How to convert a screwdriver battery to lithium-ion: step-by-step instructions. Converting a screwdriver to use Li-Ion batteries and mains power with your own hands How to convert a cordless screwdriver to Li-Ion

The advantages of cordless power tools are obvious; there is no point in discussing this issue. Negative factors include some inconveniences associated with the need to charge batteries, as well as the high cost of batteries (we are talking about high-quality energy units).

If you have to put up with charging, then manufacturers solve the second problem in a way that is not best for the consumer. Most screwdrivers in an affordable price range are equipped with nickel-cadmium batteries (Ni-Ca), the performance properties of which leave much to be desired.

The battery case contains 10-12 interconnected AA Ni-Ca batteries (typical voltage - 14 volts). Such elements have a limited service life and a rather low capacity, which is gradually lost during operation. As a result, after 2-3 years the charge retention time can decrease by 3-5 times. You have to regularly change damaged “barrels”, or even buy a new battery pack.

The best option in terms of price and quality is lithium batteries of the 18650 series. Structurally, they look like ordinary AA batteries, the size is 25% larger than the AA format.

Parameters of a typical Li-ion battery:

  • voltage 3.6-3.7 V
  • capacity from 800 to 4500 mAh
  • output current - about 35A

The optimal capacity is 2500 mAh; values ​​that are too high are not true and lead to an unjustified increase in cost. A 2500 mAh battery from a more or less decent manufacturer (for example, LG) can be bought for 300-600 rubles.

How to calculate the parameters of a new battery

  1. The current consumption of a screwdriver usually does not exceed 10-15 amperes. Accordingly, the typical output (discharge) current of a Li-ion battery (30-35A) is sufficient with a reserve.
  2. The supply voltage is calculated using an old Ni-Ca battery. Typically, the unit consists of 12 1.2 volt batteries, that is, a total value of 14.4 V. Lithium batteries cannot be discharged to a voltage below 2.74 volts. The operating voltage is 3.0-3.5 V, that is, to replace it you need to connect 4 18650 batteries in series.

The resulting operating voltage of 12 V to 14 V is more than enough. Even relatively fresh standard Ni-Ca batteries rarely produce more than 12 volts.

If space allows, you can connect 2 serial assemblies of 4 batteries in parallel, doubling the battery capacity. At the same time, the relative position can be anything - according to the shape of the body. The main thing is to ensure a reliable connection of the wires.

  1. In addition, it is advisable to place a charger in a common housing. Then you won't have to remove the batteries from the case every time.

Charger - manufacturing options

The optimal design is “all in one”. That is, the battery case contains both batteries and a charger with a 220 volt input. You simply connect the power cable and charge.

There is another option - the charger is placed in a separate case to save space (this allows you to place more batteries in the battery case).

Most chargers (we are talking about factory-made boards that can be purchased in radio stores, or on Aliexpress) are designed for a certain number of Li-ion batteries in the assembly. You simply select the appropriate option.

You can assemble such a circuit yourself if you have amateur radio skills. In this case, the cost of rework will decrease.

In any option, a charge (discharge) control device must be installed. These can be indicator LEDs or a digital display.

Built-in lithium battery monitoring

Elements of this type are sensitive to overdischarge. If the battery voltage drops below 2.75 V, degradation begins and the module loses capacity. Therefore, it is necessary to monitor the parameters during operation.

Some 18650 cells are equipped with built-in discharge control boards, and simply turn off the battery when a critical voltage value is reached. When purchasing items, you need to clarify this point. If your batteries do not have protection, you can install it additionally. Such ready-made boards are also commercially available.

The circuit is installed in the common battery housing and does not interfere with battery charging at all.

Option with a ready-made kit for vapers

18650 batteries are popular among the so-called. vapers – lovers of electronic cigarettes. Ready-made kits consisting of a charger and Li-ion batteries are available for sale. To use such a set in a screwdriver, you will have to install a container with contacts in the battery case and remove the modules for charging each time.

If the dimensions of the screwdriver body allow, and there is no desire to tinker with diagrams, this is an option for you. Of course, costs will increase slightly.

Conclusion - advantages and disadvantages of converting a screwdriver battery to lithium cells

Any modification must be economically justified. If we spend money and time, we need to understand what benefits will come from it.

Advantages of Li-ion batteries

  • The energy intensity of lithium batteries is significantly higher. Therefore, with the same dimensions and weight, the duration of battery use between recharges will be longer.
  • The charging process is faster. This means that forced downtime during recharging is reduced.
  • Unlike nickel batteries, lithium batteries do not have the so-called memory effect. They can be charged without waiting for complete discharge.

Disadvantages of replacing batteries from Ni-Ca to Li-ion:

  • First of all, the cost part. The total cost of the rework can reach 2-3 thousand rubles.
  • Dependence on external temperature: lithium batteries lose their functionality at low temperatures. Therefore, in winter, on the street, you cannot use such tools.
  • Non-standard voltage of Li-ion batteries (3.6-3.7 V) leads to inaccuracies in selecting the final value.
  • 18650 batteries differ in size from standard Ni-Ca “cans”. To place them in a standard screwdriver body, a number of design problems must be solved.

The standard screwdriver device is not suitable for charging lithium batteries. We have to make a new circuit.

I welcome everyone who stopped by. The review will focus, as you probably already guessed, on two simple headsets designed to monitor Li-Ion battery assemblies, called BMS. The review will include testing, as well as several options for converting a screwdriver for lithium based on these boards or similar ones. For anyone interested, you are welcome under cat.
Update 1, Added a test of the operating current of the boards and a short video on the red board
Update 2, Since the topic has aroused little interest, I will try to supplement the review with several more ways to remake Shurik to make a kind of simple FAQ

General form:


Brief performance characteristics of the boards:


Note:

I want to warn you right away - only the blue board has a balancer, the red one does not have a balancer, i.e. This is purely an overcharge/overdischarge/short circuit/high load current protection board. And also, contrary to some beliefs, none of them have a charge controller (CC/CV), so for their operation a special board with a fixed voltage and current limitation is required.

Board dimensions:

The dimensions of the boards are very small, only 56mm*21mm for the blue one and 50mm*22mm for the red one:




Here is a comparison with AA and 18650 batteries:


Appearance:

Let's start with:


Upon closer examination, you can see the protection controller – S8254AA and balancing components for the 3S assembly:


Unfortunately, according to the seller, the operating current is only 8A, but judging by the datasheets, one AO4407A mosfet is designed for 12A (peak 60A), and we have two of them:

I will also note that the balancing current is very small (about 40ma) and balancing is activated as soon as all cells/banks switch to CV mode (second charge phase).
Connection:


simpler, because it does not have a balancer:


It is also based on the protection controller – S8254AA, but is designed for a higher operating current of 15A (again, according to the manufacturer):


Looking at the datasheets for the power mosfets used, the operating current is stated to be 70A, and the peak current is 200A, even one mosfette is enough, but we have two of them:

The connection is similar:


So, as we can see, both boards have a protection controller with the necessary isolation, power mosfets and shunts to control the passing current, but the blue one also has a built-in balancer. I haven't looked into the circuit too much, but it looks like the power mosfets are paralleled, so the operating currents can be multiplied by two. Important note - maximum operating currents are limited by the current shunts! These scarves do not know about the charging algorithm (CC/CV). To confirm that these are precisely protection boards, one can judge by the datasheet for the S8254AA controller, in which there is not a word about the charging module:


The controller itself is designed for a 4S connection, so with some modification (judging by the datasheet) - soldering the connector and resistor, perhaps the red scarf will work:


It’s not so easy to upgrade the blue scarf to 4S; you’ll have to solder on the balancer elements.

Board testing:

So, let's move on to the most important thing, namely how suitable they are for real use. The following devices will help us for testing:
- a prefabricated module (three three/four-register voltmeters and a holder for three 18650 batteries), which appeared in my review of the charger, although without a balancing tail:


- two-register ampere-voltmeter for current monitoring (lower readings of the device):


- step-down DC/DC converter with current limiting and lithium charging capability:


- charging and balancing device iCharger 208B for discharging the entire assembly

The stand is simple - the converter board supplies a fixed constant voltage of 12.6V and limits the charging current. Using voltmeters, we look at what voltage the boards operate at and how the banks are balanced.
First, let's look at the main feature of the blue board, namely balancing. There are 3 cans in the photo, charged at 4.15V/4.18V/4.08V. As we can see, there is an imbalance. We apply voltage, the charging current gradually drops (lower gauge):


Since the scarf does not have any indicators, the completion of balancing can only be assessed by eye. The ammeter was already showing zeros more than an hour before the end. For those interested, here is a short video about how the balancer works in this board:


As a result, the banks are balanced at 4.210V/4.212V/4.206V, which is quite good:


When applying a voltage slightly higher than 12.6V, as I understand it, the balancer is inactive and as soon as the voltage on one of the cans reaches 4.25V, the S8254AA protection controller turns off the charge:


The situation is the same with the red board; the S8254AA protection controller also turns off the charge at 4.25V:


Now let's go through the load cutoff. I will discharge, as I mentioned above, with an iCharger 208B charger and balancing device in 3S mode with a current of 0.5A (for more accurate measurements). Since I don’t really want to wait for the entire battery to drain, I took one dead battery (green Samson INR18650-25R in the photo).
The blue board turns off the load as soon as the voltage on one of the cans reaches 2.7V. In the photo (no load->before shutdown->end):


As you can see, the board turns off the load at exactly 2.7V (the seller stated 2.8V). It seems to me that this is a little high, especially considering the fact that in the same screwdrivers the loads are huge, therefore, the voltage drop is large. Still, it is advisable to have a cutoff of 2.4-2.5V in such devices.
The red board, on the contrary, turns off the load as soon as the voltage on one of the cans reaches 2.5V. In the photo (no load->before shutdown->end):


Here everything is generally fine, but there is no balancer.

Update 1: Load test:
The following stand will help us with the output current:
- the same holder/holder for three 18650 batteries
- 4-register voltmeter (control of total voltage)
- car incandescent lamps as a load (unfortunately, I only have 4 incandescent lamps of 65W each, I don’t have any more)
- HoldPeak HP-890CN multimeter for measuring currents (max 20A)
- high-quality copper stranded acoustic wires of large cross-section

A few words about the stand: the batteries are connected by a “jack”, i.e. as if one after another, to reduce the length of the connecting wires, and therefore the voltage drop across them under load will be minimal:


Connecting cans on a holder (“jack”):


The probes for the multimeter were high-quality wires with crocodile clips from the iCharger 208B charger and balancing device, because HoldPeak’s do not inspire confidence, and unnecessary connections will introduce additional distortions.
First, let's test the red protection board, as it is the most interesting in terms of current load. Solder the power and can wires:


It turns out something like this (the load connections turned out to be of minimal length):


I already mentioned in the section on remaking Shurik that such holders are not really designed for such currents, but they will do for tests.
So, a stand based on a red scarf (according to measurements, no more than 15A):


Let me briefly explain: the board holds 15A, but I don’t have a suitable load to fit into this current, since the fourth lamp adds about 4.5-5A more, and this is already beyond the limits of the board. At 12.6A, the power mosfets are warm, but not hot, just right for long-term operation. At currents of more than 15A, the board goes into protection. I measured with resistors, they added a couple of amperes, but the stand was already disassembled.
A huge plus of the red board is that there is no protection blocking. Those. When the protection is triggered, it does not need to be activated by applying voltage to the output contacts. Here's a short video:


Let me explain a little. Since cold incandescent lamps have low resistance, and are also connected in parallel, the board thinks that a short circuit has occurred and the protection is triggered. But due to the fact that the board does not have a lock, you can warm up the coils a little, making a “softer” start.

The blue scarf holds more current, but at currents of more than 10A, the power mosfets get very hot. At 15A the scarf will last no more than a minute, because after 10-15 seconds the finger no longer holds the temperature. Fortunately, they cool down quickly, so they are quite suitable for short-term loads. Everything would be fine, but when the protection is triggered, the board is blocked and to unlock it, you need to apply voltage to the output contacts. This option is clearly not for a screwdriver. In total, the current is 16A, but the mosfets get very hot:


Conclusion: My personal opinion is that a regular protection board without a balancer (red) is perfect for a power tool. It has high operating currents, an optimal cut-off voltage of 2.5V, and is easily upgraded to a 4S configuration (14.4V/16.8V). I think this is the best choice for converting a budget Shurik for lithium.
Now for the blue scarf. One of the advantages is the presence of balancing, but the operating currents are still small, 12A (24A) is somewhat not enough for a Shurik with a torque of 15-25Nm, especially when the cartridge almost stops when tightening the screw. And the cutoff voltage is only 2.7V, which means that under heavy load, part of the battery capacity will remain unclaimed, since at high currents the voltage drop on the banks is significant, and they are designed for 2.5V. And the biggest disadvantage is that the board is blocked when the protection is triggered, so use in a screwdriver is undesirable. It is better to use a blue scarf in some homemade projects, but again, this is my personal opinion.

Possible application schemes or how to convert Shurik’s power supply to lithium:

So, how can you change the power supply of your favorite Shurik from NiCd to Li-Ion/Li-Pol? This topic is already quite hackneyed and solutions, in principle, have been found, but I will briefly repeat myself.
To begin with, I’ll just say one thing - in budget shuriks there is only a protection board against overcharge/overdischarge/short circuit/high load current (analogous to the red board under review). There is no balancing there. Moreover, even some branded power tools do not have balancing. The same applies to all tools that proudly say “Charge in 30 minutes.” Yes, they charge in half an hour, but the shutdown occurs as soon as the voltage on one of the banks reaches the nominal value or the protection board is triggered. It is not difficult to guess that the banks will not be fully charged, but the difference is only 5-10%, so it is not so important. The main thing to remember is that a balanced charge lasts for at least several hours. So the question arises, do you need it?

So, the most common option looks like this:
Network charger with stabilized output 12.6V and current limitation (1-2A) -> protection board ->
The bottom line: cheap, fast, acceptable, reliable. Balancing depends on the state of the cans (capacity and internal resistance). This is a completely working option, but after a while the imbalance will make itself felt in the operating time.

More correct option:
Network charger with stabilized output 12.6V, current limitation (1-2A) -> protection board with balancing -> 3 batteries connected in series
In summary: expensive, fast/slow, high quality, reliable. Balancing is normal, battery capacity is maximum

So, we’ll try to do something similar to the second option, here’s how you can do it:
1) Li-Ion/Li-Pol batteries, protection boards and a specialized charging and balancing device (iCharger, iMax). Additionally, you will have to remove the balancing connector. There are only two disadvantages - model chargers are not cheap, and they are not very convenient to service. Pros – high charging current, high can balancing current
2) Li-Ion/Li-Pol batteries, protection board with balancing, DC converter with current limiting, power supply
3) Li-Ion/Li-Pol batteries, protection board without balancing (red), DC converter with current limiting, power supply. The only downside is that over time the cans will become unbalanced. To minimize imbalance, before altering the shurik, it is necessary to adjust the voltage to the same level and it is advisable to take cans from the same batch

The first option will only work for those who have a model memory, but it seems to me that if they needed it, then they remade their Shurik a long time ago. The second and third options are practically the same and have the right to life. You just need to choose what is more important – speed or capacity. I believe that the last option is the best option, but only once every few months you need to balance the banks.

So, enough chatter, let's get to the remodeling. Since I don’t have experience with NiCd batteries, I’m talking about the conversion only in words. We will need:

1) Power supply:

First option. Power supply (PSU) at least 14V or more. The output current is desirable to be at least 1A (ideally about 2-3A). We will use a power supply from laptops/netbooks, from chargers (output more than 14V), units for powering LED strips, video recording equipment (DIY power supply), for example, or:


- Step-down DC/DC converter with current limiting and the ability to charge lithium, for example or:


- Second option. Ready-made power supplies for Shuriks with current limiting and 12.6V output. They are not cheap, as an example from my review of the MNT screwdriver -:


- Third option. :


2) Protection board with or without balancer. It is advisable to take the current with a reserve:


If the option without a balancer is used, then it is necessary to solder the balancing connector. This is necessary to control the voltage on the banks, i.e. to assess imbalance. And as you understand, you will need to periodically recharge the battery one by one with a simple TP4056 charging module if imbalance begins. Those. Once every few months, we take the TP4056 scarf and charge one by one all the banks that, at the end of the charge, have a voltage below 4.18V. This module correctly cuts off the charge at a fixed voltage of 4.2V. This procedure will take an hour and a half, but the banks will be more or less balanced.
It’s written a little chaotically, but for those in the tank:
After a couple of months, we charge the screwdriver battery. At the end of the charge, we take out the balancing tail and measure the voltage on the banks. If you get something like this - 4.20V/4.18V/4.19V, then balancing is basically not needed. But if the picture is as follows - 4.20V/4.06V/4.14V, then we take the TP4056 module and charge two banks in turn to 4.2V. I don’t see any other option other than specialized chargers-balancers.

3) High current batteries:


I have previously written a couple of short reviews about some of them - and. Here are the main models of high-current 18650 Li-Ion batteries:
- Sanyo UR18650W2 1500mah (20A max.)
- Sanyo UR18650RX 2000mah (20A max.)
- Sanyo UR18650NSX 2500mah (20A max.)
- Samsung INR18650-15L 1500mah (18A max.)
- Samsung INR18650-20R 2000mah (22A max.)
- Samsung INR18650-25R 2500mah (20A max.)
- Samsung INR18650-30Q 3000mah (15A max.)
- LG INR18650HB6 1500mah (30A max.)
- LG INR18650HD2 2000mah (25A max.)
- LG INR18650HD2C 2100mah (20A max.)
- LG INR18650HE2 2500mah (20A max.)
- LG INR18650HE4 2500mah (20A max.)
- LG INR18650HG2 3000mah (20A max.)
- SONY US18650VTC3 1600mah (30A max.)
- SONY US18650VTC4 2100mah (30A max.)
- SONY US18650VTC5 2600mah (30A max.)

I recommend the time-tested cheap Samsung INR18650-25R 2500mah (20A max), Samsung INR18650-30Q 3000mah (15A max) or LG INR18650HG2 3000mah (20A max). I haven’t had much experience with other jars, but my personal choice is Samsung INR18650-30Q 3000mah. The Skis had a small technological defect and fakes with low current output began to appear. I can post an article on how to distinguish a fake from an original, but a little later, you need to look for it.

How to put all this together:


Well, a few words about the connection. We use high-quality copper stranded wires with a decent cross-section. These are high-quality acoustic or ordinary SHVVP/PVS with a cross-section of 0.5 or 0.75 mm2 from a hardware store (we rip the insulation and get high-quality wires of different colors). The length of the connecting conductors should be kept to a minimum. Batteries preferably from the same batch. Before connecting them, it is advisable to charge them to the same voltage so that there is no imbalance for as long as possible. Soldering batteries is not difficult. The main thing is to have a powerful soldering iron (60-80W) and an active flux (soldering acid, for example). Solders with a bang. The main thing is to then wipe the soldering area with alcohol or acetone. The batteries themselves are placed in the battery compartment from old NiCd cans. It is better to arrange it in a triangle, minus to plus, or as popularly called “jack”, by analogy with this (one battery will be located in reverse), or there is a good explanation a little higher (in the testing section):


Thus, the wires connecting the batteries will be short, therefore, the drop in precious voltage in them under load will be minimal. I do not recommend using holders for 3-4 batteries; they are not intended for such currents. Side-by-side and balancing conductors are not so important and can be of smaller cross-section. Ideally, it is better to stuff the batteries and the protection board into the battery compartment, and the step-down DC converter separately into the docking station. The charge/charged LED indicators can be replaced with your own and displayed on the docking station body. If you wish, you can add a minivoltmeter to the battery module, but this is extra money, because the total voltage on the battery will only indirectly indicate the residual capacity. But if you want, why not. Here :

Now let's estimate the prices:
1) BP – from 5 to 7 dollars
2) DC/DC converter – from 2 to 4 dollars
3) Protection boards - from 5 to 6 dollars
4) Batteries – from 9 to 12 dollars ($3-4 per item)

Total, on average, $15-20 for a remodel (with discounts/coupons), or $25 without them.

Update 2, a few more ways to remake Shurik:

The next option (suggested from the comments, thanks I_R_O And cartmann):
Use inexpensive 2S-3S type chargers (this is the manufacturer of the same iMax B6) or all kinds of copies of B3/B3 AC/imax RC B3 () or ()
The original SkyRC e3 has a charging current per cell of 1.2A versus 0.8A for copies, should be accurate and reliable, but twice as expensive as copies. You can buy it very inexpensively at the same place. As I understand from the description, it has 3 independent charging modules, something akin to 3 TP4056 modules. Those. SkyRC e3 and its copies do not have balancing as such, but simply charge the banks to one voltage value (4.2V) at the same time, since they do not have power connectors. SkyRC's assortment actually includes charging and balancing devices, for example, but the balancing current is only 200mA and costs around $15-20, but it can charge life-changing devices (LiFeP04) and charge currents up to 3A. Those who are interested can familiarize themselves with the model range.
In total, for this option you need any of the above 2S-3S chargers, a red or similar (without balancing) protection board and high-current batteries:


As for me, it’s a very good and economical option, I’d probably stick with it.

Another option suggested by comrade Volosaty:
Use the so-called “Czech balancer”:

It’s better to ask him where it’s sold, it’s the first time I’ve heard about it :-). I can’t tell you anything about currents, but judging by the description, it needs a power source, so the option is not so budget-friendly, but seems interesting in terms of charging current. Here is the link to. In total, for this option you need: a power supply, a red or similar (without balancing) protection board, a “Czech balancer” and high-current batteries.

Advantages:
I have already mentioned the advantages of lithium power supplies (Li-Ion/Li-Pol) over nickel ones (NiCd). In our case, a head-to-head comparison – a typical Shurik battery made of NiCd batteries versus lithium:
+ high energy density. A typical 12S 14.4V 1300mah nickel battery has a stored energy of 14.4*1.3=18.72Wh, while a 4S 18650 14.4V 3000mah lithium battery has a stored energy of 14.4*3=43.2Wh
+ no memory effect, i.e. you can charge them at any time without waiting for complete discharge
+ smaller dimensions and weight with the same parameters as NiCd
+ fast charging time (not afraid of high charge currents) and clear indication
+ low self-discharge

The only disadvantages of Li-Ion are:
- low frost resistance of batteries (they are afraid of negative temperatures)
- balancing of the cans during charging and the presence of overdischarge protection is required
As you can see, the advantages of lithium are obvious, so it often makes sense to rework the power supply...

Conclusion: The scarves under review are not bad, they should be suitable for any task. If I had a shurik on NiCd cans, I would choose a red scarf for conversion, :-)…

The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.

Has the meaning. The advantage is that they have a high electrical density. As a result, by installing such a device in the screwdriver body, we can achieve an increase in the operating time of the tool many times over. The charging current for high-power lithium batteries, especially for new modifications, can reach 1-2 C. Such a device can be recharged in 1 hour, without exceeding the parameters recommended by the manufacturer and without spoiling the quality of the product.

What do lithium batteries look like?

Most lithium devices are housed in a prismatic body, but some models are cylindrical. These batteries use roll electrodes and separators. The body is made of aluminum or steel. The positive pole goes to the housing cover.

In prismatic configurations, the electrodes are in the form of rectangular plates. To ensure safety, the battery is equipped with a device that acts as a regulator of all processes and opens the electrical circuit in critical situations. Increased sealing of the housing prevents electrolyte from leaking out and oxygen and moisture from penetrating inside.

What precautions should be taken to avoid damaging the lithium battery?

  • Due to technology limitations, the charge level of lithium batteries should not be higher than 4.25-4.35 V. The discharge should not reach 2.5-2.7. This condition is indicated in the technical data sheet for each specific model. If these values ​​are too high, you may damage the device. Special charge and discharge controllers are used that keep the voltage on the lithium cell within normal limits. Converting the screwdriver to a lithium battery with a controller will protect the device from malfunction.
  • The voltage of lithium batteries is a multiple of 3.7 V (3.6 V). For Ni-Mh models this figure is 1.2 V. This phenomenon is understandable. in lithium devices it is stored in a separate cell. The 12 volt lithium battery will never be assembled. The rating will be 11.1V (three cells in series) or 14.8V (four cells in series). In addition, the voltage indicator of the lithium cell changes when operating when fully charged by 4.25 V, and when fully discharged - by 2.5 V. The voltage indicator 3S (3 serial - three serial connections) will change when the device is operating from 12.6 V (4.2x3) to 7.5 V (2.5x3). For the 4S configuration, this figure ranges from 16.8 to 10 V.
  • Converting a screwdriver to 18650 lithium batteries (the vast majority of products have this exact size) requires taking into account the difference in dimensions with Ni-Mh cells. The cell diameter 18650 is 18 mm and the height is 65 mm. It is very important to calculate how many cells will fit in the case. It should be remembered that for a model with a power of 11.1 V you will need a number of cells that is a multiple of three. For a model with a power of 14.8 V - four. The controller and patching wires must also fit.
  • The charging device for a lithium-based battery differs from the device for Ni-Mh modifications.

The article will discuss how to convert a screwdriver to lithium. The tool is equipped with a pair of Ni-Mh rechargeable batteries with a voltage of 12 V and a capacity of 2.6 Ah. Hitachi screwdriver conversion will be considered. Lithium batteries will provide the device with long-term service.

Selecting the nominal voltage

First of all, you should decide on the choice of voltage rating for a lithium-based device. The choice should be made between the 3S model (its voltage range is from 12.6 to 7.5 V) and the 4S-Li-Ion battery (voltage range is from 16.8 to 10 V).

Advantages of the second option

The second option is more suitable because the voltage in the battery drops quite quickly from maximum to minimum (from 16.8 to 14.8 V). For an electric motor, which, strictly speaking, is a screwdriver, exceeding 2.8 V is not a critical level.

The lowest voltage indicator is for the 3S-Li-Ion modification. It is equal to 7.5 V, which is insufficient for the normal functioning of the electrical device. By mounting four configurations, we will increase the battery capacity.

How to decide on the choice of lithium cells?

To select lithium-based cells, limiting factors must be identified. Currently, lithium devices are produced with a permissible current load value of 20-25 A.

Pulse current values ​​(short, up to 1-2 seconds) reach 30-35 A. The battery configuration will not be damaged.

How many cells will fit in the case?

It will not be possible to assemble 4S2P (four serial connections and two parallel ones). Converting a screwdriver to 18650 lithium batteries assumes the presence of eight cells. How can they make it to four? Each cell will bear the maximum current load.

How to determine the maximum current in a screwdriver?

Converting a 12V screwdriver to lithium batteries involves connecting the device to a laboratory power source with a maximum current of 30 A. The limiter regulator is set to the maximum value. Having created the voltage level of the power source close to the nominal value of the future battery, we begin to smoothly pull the trigger. The current consumed by the screwdriver will rise to 5 A. Now you should sharply pull the trigger. This will short out the power circuit. The current will reach a power of 20-30 A. Perhaps its indicator would be much higher, but the power of the power source will not allow this to be recorded. This will be a short-term load current when you sharply press the trigger of the screwdriver. Any model of such a device will react similarly.

Next, you should clamp the tip of the screwdriver with a vice and observe to what value the current consumption will increase during the operating mode when the ratchet in the screwdriver is activated. The current indicator in this case increases to 10-12 A.

This way you can determine the value of the load current. In this case, it will be equal to 5 A at idle and 30 A at a sharp start, and at maximum load it will be 12 A. The manufacturer must select lithium cells whose nominal load current will be 10-20 A, and the pulse current - 25-30 A.

How to choose a controller?

So, the screwdriver is being converted to lithium batteries. Regular charging for the device is required. When choosing a controller, please note that the device must meet two parameters:

  • rated operating voltage indicator;
  • rated operating current.

With voltage, everything is very clear: if the battery is 11.1 V, then the controller will have the same voltage.

The term “rated operating current” refers to the protection capacity of the board. Thus, a 4 A controller is designed for a current mark of 4 A, and at 8 A an additional load is placed on it. In this case, the protective device will operate. All these technical data are presented in the passport of each controller modification. In this case, one modification may have a limiting current indicator of 30 A, and another - 50 A. And both of these devices will formally be suitable for operation. Also, when creating a lithium battery, there is a limitation in size. Therefore, you should purchase a controller that will fit in the body of an old battery.

Disassembly and assembly

Converting a screwdriver to lithium batteries includes the following steps:

  • You should open the old battery by unscrewing five screws.
  • Remove the Ni-Mh battery from the housing. It will be noticeable that the contact pad that engages with the contact group of the screwdriver is welded to the negative contact of one of the Ni-Mh cells. Welding points should be cut using a tool with a cutting stone built into it
  • Wires are soldered to the contacts, the cross-section of which is at least 2 mm 2 for power terminals and 0.2 mm 2 for the thermistor. The contact pad is glued into the battery case using hot-melt adhesive.
  • Based on the internal resistance indicator, four cells are selected on the meter. The value must be the same for all four devices.
  • Lithium cells are glued together with hot glue so that they are compactly located in the housing.
  • Welding of cells is carried out on a resistance welding machine using a nickel welding tape (its cross-section should be 2X10 mm).

Installing the protection board

This stage can show how lightweight the lithium battery design is. The weight of the Ni-Mh device was 536 g. The weight of the new lithium device is 199 g, which will be quite noticeable. We managed to win 337 g in weight. At the same time, an increase in energy capacity is observed.

The battery is mounted in the housing. The voids are filled with soft material from the packaging.

Connection to a screwdriver

  • A sharp pull on the trigger triggers the current protection mechanism. But in reality, such a protective mode is unlikely to be needed when using the tool. If you do not specifically provoke the defense, the operation of the screwdriver will be stable.
  • The tip should be clamped in a vice. The battery power freely activates the ratchet, which limits the increase in rotation speed.
  • The screwdriver is discharged by The discharge current indicator should be 5 A.
  • The battery is inserted into the standard charger. The measured charge current is 3 A, which is acceptable for lithium cells. For the LG INR18650HG2 configuration, the maximum charge current will be 4 A, which is indicated in the technical specifications.

How long does it take to replace batteries?

Converting a screwdriver to lithium batteries will take approximately 2 hours. If all parameters are checked, then it will take 4 hours.

You can do everything yourself, without the help of another person. But resistance welding and selection of batteries cannot be carried out without specialized equipment.

How else can you test the degree of charge besides the controller?

The screwdriver has been converted to use lithium batteries. The standard charger built into the case is an ideal option. But the cost of the controller is quite high. The device will cost $30, which is the same as the cost of the battery itself.

To test the charge level of a lithium battery on the go, without using a charger, you can use a special indicator RC helicopter lipo battery AKKU portable voltage meter tester alarm 2-6S AOK. The cost of the device is very low. It has a balancing and charging connector similar to the iMax6 device. The device is connected to the battery using an adapter. This voltage level control device is very convenient. It can measure from two to six lithium cells connected in series, and also give the total indicator or voltage of each element separately with extreme accuracy.

How much will it cost to replace a Ni-Mh with a lithium device?

What financial costs will it require to convert a screwdriver to a lithium battery?

The price of such a device consists of the cost of several components:

  • the lithium-based 4S battery configuration costs RUB 2,200;
  • purchasing a controller for charging and discharging plus a balancer costs 1,240 rubles;
  • the cost of welding and assembly is 800 rubles.

It turns out that a do-it-yourself lithium battery costs 4,240 rubles.

For comparison, let's take a similar configuration from factory-produced lithium. For example, the Makita 194065-3 device is designed for a screwdriver. It has similar parameters. The cost of such a device is 6500 rubles. It turns out that converting a screwdriver to lithium batteries saves 2,300 rubles.

The cost of a new screwdriver is approximately 70% the cost of its battery. Therefore, it is not surprising when, faced with a battery failure, we ask ourselves the question - what next? Should I buy a new battery or screwdriver, or maybe there is an opportunity to repair the screwdriver battery with my own hands and continue working with an already familiar tool?

In this article, which we will conditionally divide into three parts, we will consider: the types of batteries that are used in screwdrivers (part 1), their possible causes of failure (part 2) and available repair methods (part 3).

Screwdriver battery: design and types

It should be noted that regardless of the brand of screwdriver and the country of manufacture, the batteries have an identical structure. The assembled battery pack looks like this.

If we take it apart, we will see that it is assembled from small elements that are assembled sequentially. And from the school physics course we know that elements that are connected in series balance their potentials.

Note. The sum of each battery element gives us the final voltage at the battery contacts.

Set-up parts or “cans”, as a rule, have a standard size and voltage; they differ only in capacity. Battery capacity is measured in Ah and is indicated on the cell (shown below).

The following types of elements are used to assemble screwdriver batteries:

  • nickel - cadmium (Ni - Cd) batteries, with a nominal voltage on the “banks” of 1.2V;
  • nickel-metal hydride (Ni-MH), element voltage - 1.2V;
  • lithium-ion (Li-Ion), with a voltage of 3.6V.

Let's take a closer look at the advantages and disadvantages of each type.

  • The most common type due to its low cost;
  • Low temperatures are not scary, for example, like Li-Ion batteries;
  • It is stored in a discharged state, while retaining its characteristics.
  • Produced only in third world countries due to toxicity during production;
  • Memory effect;
  • Self-discharge;
  • Small capacity;
  • A small number of charge/discharge cycles means they do not “live” for a long time with intensive use.
  • Environmentally friendly production, it is possible to purchase a high-quality branded battery;
  • Low memory effect;
  • Low self-discharge;
  • Large capacity compared to Ni - Cd;
  • More charge/discharge cycles.
  • Price;
  • Loses some of its characteristics when stored for a long time in a discharged state;
  • At low temperatures it does not “live” for long.
  • No memory effect;
  • Almost no self-discharge;
  • High battery capacity;
  • The number of charge/discharge cycles is many times greater than that of previous types of batteries;
  • To set the required voltage, a smaller number of “cans” are needed, which significantly reduces the weight and dimensions of the battery.
  • High price, almost 3 times compared to nickel-cadmium;
  • After three years, a significant loss of capacity occurs, because Li decomposes.

We have become familiar with the elements, let's move on to the remaining elements of the screwdriver battery pack. Disassembling the unit, for example, to repair the battery of a Hitachi screwdriver (shown below), is very simple - unscrew the screws around the perimeter and disconnect the case.

The housing has four contacts:

  • Two power ones, “+” and “-”, for charge/discharge;
  • The upper control is switched on via a temperature sensor (thermistor). The thermistor is necessary to protect the batteries; it turns off or limits the charging current when a certain temperature of the elements is exceeded (usually in the range of 50 - 600C). Heating occurs due to high currents during forced charging, the so-called “fast” charging;
  • The so-called “service” contact, which is connected through a 9Kohm resistance. It is used for complex charging stations that equalize the charge across all battery cells. In everyday life, such stations are useless due to their high cost.

That's the whole design of the battery. Below is a video on how to disassemble the block.

Troubleshooting

We have figured out the purpose of the battery design elements, now let’s look at how to determine the malfunction, this is part 2 of repairing a screwdriver battery. Let us immediately note that all elements cannot fail at once, and since our circuit is sequential, if one element fails, the entire circuit does not work. This means our task is to determine where the weakest link is in our chain.

​

To do this, we will need a multimeter, and for the second method of troubleshooting, a 12V lamp, if your battery for the screwdriver is also 12 volt. The procedure is as follows:

We put the battery on charge and wait for a signal about full charge.

We disassemble the case and measure on each battery bank. For Ni - Cd we should have 1.2 - 1.4V, for lithium - 3.6/3.8V.

Mark all “banks” in which the voltage is less than the nominal voltage. For example, most Ni-Cd elements have a voltage of 1.3V, and one or more have a voltage of 1.2/1.1V.

We assemble the battery and work until there is a noticeable loss of power.

We remove, disassemble and measure the voltage drop on the battery “banks”. On the marked elements the voltage “sag” will be greater than on others. For example, they are no longer 1.2V, but 1.0V or even lower.

Note. A difference between the elements in a battery of 0.5 - 0.7V is considered significant, which means that the element becomes unusable.

Thus, we found candidates for “reanimation” or “amputation” and replacement with new elements.

If your screwdriver operates on a voltage of 12 or 13V, you can search using a simpler method. We disassemble a fully charged battery and connect a 12 volt lamp to the “+” and “-” contacts. The lamp will be a load and will drain the battery. Next, we take measurements on the battery elements, where the voltage drop is greatest, there is a weak link.

There are other ways, instead of a lamp you can select a resistance, but this already requires the basics of electrical engineering, and it is doubtful that a resistor with the necessary resistance would be at hand.

Other malfunctions are very rare. For example, loss of contact in the soldering areas of batteries or power contacts of the unit, failure of the thermistor. This problem is more common with fakes. Due to its rarity, we will not focus on the battery elements.

The “problematic” elements have been dealt with and need to be repaired. How to repair a screwdriver battery? In general, there are 2 methods available for repair, so to speak. This is the restoration and replacement of elements that have become unusable.

Is it possible to “reanimate” elements and how?

Let's proceed to Part 3 of screwdriver battery repair and immediately make a reservation that the concept of “reanimation” for lithium-ion batteries is not applicable. There is no memory effect in them; most likely, lithium decomposition has occurred, and nothing can be done about it. In such batteries, it is necessary to find out what is the cause of the malfunction: the element itself or the control circuit. There are two options here:

  • we change the control circuit from another, but similar to ours, battery, if it helps, we find a replacement and change it;
  • supply 4V to the element with a current of approximately 200mA, for this you need a regulated charger. If the voltage on the element increases to 3.6V, the element is working properly, the problem is in other elements, or in the control circuit.

Screwdriver battery repair is available primarily for Ni-Cd batteries, but they are usually the most common in household screwdrivers.

So, how to reanimate a screwdriver battery? There are two types of “reanimation” for these types of batteries:

  1. Compaction or compression method (this will work in cases where the electrolyte is still available, but volume has been lost);
  2. “Firmware” with voltage and current greater than the nominal one. This method allows you to eliminate the memory effect, and although not completely, restore the lost capacity.

This method is shown in the video below.

Note. As a rule, in a nickel-cadmium battery the main reason for loss of capacity is boiling away of the electrolyte, and if it is critically low, no amount of “firmware” will help.

This method, if its result is positive, will not solve the problem of element failure. Rather, it will only delay the replacement of those that have become unusable, and in the future you will still need to repair the battery of a Makita screwdriver or any other.

Repair and replacement of screwdriver battery elements

A more effective way to repair batteries for a screwdriver is to replace the elements that we have identified as faulty.

To carry out repairs, we need either a “donor” battery, in which some of the elements are working, or new “banks”. Purchasing them will not be difficult; even on the Internet you can easily find a dozen stores that are ready to send these items by mail. The price is not particularly bad, for example, a nickel-cadmium cell with a capacity of 2000 mAh costs around 100 rubles.

Note. When purchasing a new element, make sure that its capacity and dimensions match the original elements.

We will also need a soldering iron, low-corrosive flux (preferably alcohol flux with rosin) and tin. We are not talking about spot welding, since for a one-time battery repair there is hardly a need to purchase or assemble it...

There is nothing complicated about the replacement itself, especially if you have at least some experience in soldering. The photographs show everything in sufficient detail; we cut off the faulty element and solder a new one in its place.

Several points need to be noted:

  • When soldering with a soldering iron, try to solder quickly so that the battery does not heat up, because you risk ruining it;
  • if possible, make the connection using original plates, or use copper plates of the same size, this is important because the charging currents are large and if the connecting wires are of the wrong cross-section, they will heat up, and accordingly the thermistor protection will be triggered;
  • Do not under any circumstances confuse the plus of the battery with the minus - the connection is in series, which means that the minus of the previous can goes to the plus of the new can, and the minus of the new one goes to the plus of the next one.

After the new elements have been soldered, it is necessary to equalize the potentials on the “banks”, since they are different. We carry out a charge/discharge cycle: set it to charge overnight, give it a day to cool down and measure the voltage on the elements. If we did everything correctly, the picture will be something like this: all elements have the same multimeter reading, within 1.3V.

Next, we proceed to discharge the battery, insert the battery into the screwdriver and load it “to its fullest.” The main thing is to spare the screwdriver itself, otherwise you will have to repair it too. We bring it to full discharge. We repeat this procedure two more times, i.e. charge and completely discharge.

It should be noted that the procedure for erasing the “memory effect” should be carried out once every three months. It is carried out in a similar way to the training described above.

This not-so-tricky procedure will prolong the operation of your screwdriver, at least until it has to be replaced with a new one.

“How much will it cost to replace the old nickel batteries with lithium-ion batteries in my screwdriver” is perhaps one of the most popular questions we hear from our customers.
And indeed, the problem is quite common. Many people have an old cordless screwdriver (wrench, hammer drill, jigsaw, trimmer, etc.) in which the standard batteries are out of order, and there is either no way to buy new ones, since they may be discontinued or you simply don’t want to spend money on outdated technology, but I want to immediately replace Ni-Mh batteries with Li-Ion and give, often, expensive and high-quality power tools a second life.

There are indeed many reasons for such a desire:
- the first and main thing is that Li-Ion batteries have a much higher electrical density than Ni-Mh batteries.
Simply put, with the same weight, a Li-Ion battery will have a higher electrical capacity than a Ni-Mh battery. Accordingly, by installing Li-ion batteries in the old case, we get a much longer operating time of the tool.

The charge current for high-power Li-ion batteries, especially for new models, can reach values ​​of 1C - 2C (single or double capacity value).
Those. such a battery can be charged in 1 - 0.5 hours, without exceeding the parameters recommended by the manufacturer and, accordingly, without reducing the battery life.

But there are enough stopping factors to implement such an idea:
- Due to technological limitations, Li-ion batteries cannot be charged above 4.25-4.35V and discharged below 2.5-2.7V (indicated in the technical specifications for each specific battery). Exceeding these values ​​may damage the battery and render it inoperable. To protect the Li-Ion battery, special charge-discharge controllers are used that keep the voltage on the Li-Ion cell within the permitted limits. That is, in addition to the batteries themselves, you will also need a charge-discharge controller.
- The voltage of Li-ion batteries is always a multiple of 3.7V (3.6V), while for Ni-Mh batteries it is a multiple of 1.2V. This is due to the rated voltage (the voltage value that is maintained on the Li-Ion battery for a sufficiently long time in the middle of the current-voltage characteristic of the discharge curve) on an individual cell. For Li-ion batteries this voltage is 3.7V, for Ni-Mh batteries it is 1.2V. Therefore, you will never be able to assemble a 12V battery from Li-Ion batteries. In nominal terms, it can be 11.1V (3 in series) or 14.8V (4 in series). Moreover, the voltage of the Li-Ion cell changes during operation from fully charged - 4.25V to completely discharged -2.5V. Thus, the voltage of the 3S (3 serial - 3 serial connections) battery will change during operation from 12.6V (4.2x3) to 7.5V (2.5x3). For 4S batteries - from 16.8V to 10V.
- Li-Ion battery size 18650, and 99 percent of all Li-Ion batteries consist of cells size 18650, has different overall dimensions from Ni-Mh cells. The 18650 cell measures 18mm in diameter and 65mm in height. It is important to “estimate” how many Li-Ion cells will fit into your case. At the same time, you need to understand that for an 11.1V battery you will need a number of Li-ion cells that is a multiple of 3. For a 14.8V battery - four. In this case, there should be space left for placing the charge-discharge controller and switching wires.
- The charger for Li-ion batteries differs from the charger for Ni-Mh batteries. To be fair, it should be noted that the chargers supplied with many screwdrivers are universal chargers and can charge both NI-Cd, Ni-Mh and Li-ion batteries. Make sure your memory has this capability.
- Cost of Li-ion batteries. and it, compared to Ni-Mh batteries, can differ significantly.

If all of the above does not scare you away, then consider an example of the process of manufacturing a Li-Ion battery to replace the Ni-Mh battery we have from a DEWALT DC840 impact wrench.

This impact wrench is equipped with two Ni-Mh rechargeable batteries with a voltage of 12V and a capacity of 2.6Ah.

To begin with, we will decide on the choice of nominal voltage for our Li-ion battery.

The choice is between a 3S Li-ion battery with a voltage range of 12.6V - 7.5V and a 4S Li-Ion battery with a voltage range of 16.8V - 10V.
We will focus on the second option, because:
a) The voltage on the battery drops quite quickly from maximum to nominal, i.e. from 16.8V to 14.8V, and for an electric motor, which is what a wrench actually is, an excess of 2.8V is not critical.
b) The minimum voltage of a 3S Li-Ion battery will be 7.5V, which is extremely low for normal operation of the power tool. And the efficiency of a 4S battery in this case will be higher than the efficiency of a 3S Li-Ion battery.
c) By installing 4 Li-ion cells, we will thereby increase the electrical capacity of our battery.

So, we’ve sorted out point 1: we’re making a 4S (14.8V) Li-Ion battery.

Second. We decide on the choice of Li-ion cells.

To do this, we need to identify the limiting factors.
In the case of the manufacture of Li-Ion batteries for power tools, the main limitation is the maximum load current. Currently, there are Li-Ion batteries with a permissible rated (long-term) load current of 20-25A. Pulse (short-term, up to 1-2 seconds) load current values ​​can reach 30-35A. In this case, you will not damage the structure of the battery.

Up to 6 Li-Ion 18650 cells can comfortably fit into our case from an old Ni-Mh battery. Accordingly, we cannot assemble a 4S2P (4 serial connections and 2 parallel) Li-ion battery, which will require 8 cells but must fit into 4 cells . Naturally, in this case, each of the cells must “hold” a single value of the maximum load current throughout the entire range of operating modes of the power tool.

We determine the maximum current flowing in the battery during operation of the impact wrench.
The video below shows that we connected the impact wrench to a laboratory power supply (PS) with a maximum current of 30A. We set the maximum current limiter regulator to the maximum possible value. Having set the IP voltage close to the nominal voltage of our future battery, we begin to smoothly pull the trigger. Current consumed by the impact wrench. rises to 5A.

Now we pull the trigger very sharply - thereby we practically “short-circuit” the power circuit. The current pulses up to 20 - 30A. Maybe he would have flown higher, but the power of the IP does not allow him to see this. You must understand that this will be a short-term load current in the event of a very sharp pull on the trigger of the impact wrench. And any screwdriver/anything with an electric motor will behave exactly this way. That’s why it’s funny to hear buyers’ statements, saying that you have non-working controllers and bad batteries, because, you see, my screwdriver consumes only 4A - I measured it - and I took Samsung 22F batteries with a capacity of 2200 mAh (the cheapest with the maximum current of 3A) and a controller of 8A and nothing works for me... And unprotected Li-ion batteries and controllers are not subject to exchange/return. Here, I think, everything is clear... Ignorance of the laws does not exempt you from responsibility...
Now let’s clamp the tip of the impact wrench into a fixed vice and see to what value the current consumption will increase under operating modes when the ratchet in the impact wrench is activated. The current value jumps to 10-12A.


At this stage, we have decided on the load current value. In our case, it will be: at idle 5A, with a sharp start 30A, at maximum load - 12A. Respectively. we choose Li-ion cells with a rated load current of 10-20A and a pulse current of 25-30A.

Li-ion battery models are suitable for us (in stock at the time of writing): 18650 2000mAh LG INR18650HD2 3.7V 25A, 18650 2500mAh LG ICR18650HE4 3.7V 20A, 18650 2600mAh SONY US18650VTC5 3.6V 30 A, 18650 3000mAh LG INR18650HG2 3, 7V 20A.

We settled on the 18650 3000mAh LG INR18650HG2 3.7V 20A for maximum capacity.

Selecting a controller (overdischarge-overcharge protection board).

The controller must satisfy two parameters:

Rated operating voltage (in our case 14.8V)
rated operating current.

With voltage, everything is clear: if the battery is 14.8V, then the controller should be 14.8V, if the battery is 11.1V, then the controller should be selected with a nominal voltage of 11.1V.

The "rated operating current" parameter determines the "throughput" of the protection board. Those. The 4A controller is designed for a current of 4A and at 8A it will have overload protection. A controller with a 16A rated load will “go into protection” at 30±10A. All these parameters are indicated on the "Characteristics" tab for each specific controller model.

In this case, for one controller instance the limiting current may be 30A and for another 50A. And both of these controllers will be formally operational. But we are also limited in size, so the controller should be chosen in such a way that it fits into your case from an old battery.

Based on the conditions described above, we chose a protection board for a 14.8V battery model HCX-D177 with a rated operating current of 16A and a maximum current threshold of 30±10A.

So, we have decided on the components for our Li-ion battery. There were no problems with the charger, since it is designed to work with both Ni-Mh and Li-ion batteries.



Plus, provided that we install a charge-discharge controller, we are insured against overcharging our battery.

Let's begin the disassembly and assembly process.

We open the old battery by unscrewing 5 screws.

We take out the old Ni-Mh battery

It can be seen that the contact pad, which engages with the contact group of the impact wrench, is welded to the plane of the negative contact of one of the Ni-Mh cells.

We cut off the weld points using a DREMEL 4000 multi-tool with a cutting stone installed. As a result, we are left with a direct contact group from the battery.

We solder wires with a cross-section of at least 2mm2 for power terminals and 0.2mm2 for connecting the thermistor to the contacts and glue the contact pad into the battery case using hot-melt adhesive.

We select 4 LG INR18650HG2 3000mAh cells based on internal resistance using a battery internal resistance meter. Its value should be the same for all four batteries in our battery.

We glue the Li-Ion cells of LG INR18650HG2 with hot glue in such a way as to ensure the most convenient location in the case.




We weld the cells on a resistance welding machine using nickel welding tape with a cross-section of 2x10mm.


Install the protection board.





At this stage, we can already estimate how much we have lightened the weight of our battery.



The weight of old Ni-Mh batteries was 536 g. The weight of the new Li-Ion battery is 199g. Thus, the weight gain is 337 grams, which is quite noticeable during operation. At the same time, our energy capacity increases from 31.2Wh (12V * 2.6Ah) in the original Ni-Mh battery to 44.4Wh (14.8V * 3Ah)

Install the battery into the case. We fill the voids with soft packaging material.

Battery ready

We connect it to our impact wrench.

The video demonstrates that when the trigger is pulled sharply, the current protection on our protection board is triggered. But in real conditions, this mode will most likely not be used. If you do not specifically try to force the protection to operate, the impact wrench behaves absolutely predictably.
We clamp the tip into the jaws of the vice. As expected, the battery power is more than enough to activate the ratchet, which limits the torsional force.

We discharge the Li-ion battery of our impact wrench on an electronic load. The discharge current is set to 5A. The discharge graph is shown in the illustration below.

We insert the battery into the standard charger. The charge current, when measured, was 3A, which fits within the permissible charge current values ​​for these Li-ion cells (for LG INR18650HG2 the maximum charge current is 4A, which is indicated on the Characteristics tab).

In terms of time, the work of replacing Ni-Mh batteries with Li-Ion batteries took about 2 hours (with checking all parameters on the equipment - about 4 hours). In principle, all this can be done on your own, but resistance welding and selection of batteries cannot be done without special equipment.

The cost of replacing a Ni-Mh battery with Li-Ion.

Let's see what we get in terms of cost:
- the cost of 4 Li-ion batteries 18650 3000mAh LG INR18650HG2 3.7V 20A, at the time of writing, is 4 x 550 rubles = 2200 rubles
- the cost of a charge-discharge controller with a balancer HCX-D177 is 1240 rubles
- the cost of welding and assembly work is 800 rubles

In total, it turns out that a homemade Li-ion battery 14.8V 3Ah costs 4240 rubles

Let's find a similar factory-made Li-Ion battery for some other screwdriver. The Makita 194065-3 battery has absolutely identical parameters.


At the time of writing, such a battery cost from 5,500 rubles to 6,500 rubles.

It turns out that direct savings amount to 1300 to 2300 rubles. And, at the same time, we should not forget that the battery we made is impossible to buy in principle!

The company Reserve Power carries out work on converting Ni-Mh batteries from screwdrivers to Li-Ion. You can calculate the cost yourself in the same way as we did above, i.e. the total cost of batteries, controller and cost of work.

The warranty for the services provided is 6 months. The guarantee is provided only if the work was carried out using our components

PS. Special thanks for providing the experimental impact wrench and moral support :) to the company

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