The cordless tool is more mobile and easier to use compared to its networked counterparts. But we must not forget about the significant disadvantage of cordless tools; as you yourself understand, the fragility of batteries. Buying new batteries separately is comparable in price to purchasing a new tool.

After four years of service, my first screwdriver, or rather the batteries, began to lose capacity. To begin with, I assembled one from two batteries by choosing working “banks,” but this modernization did not last long. I converted my screwdriver to a corded one - it turned out to be very inconvenient. I had to buy the same, but new 12 volt “Interskol DA-12ER”. The batteries in the new screwdriver lasted even less. As a result, two working screwdrivers and more than one working battery.

There is a lot written on the Internet about how to solve this problem. It is proposed to convert old Ni-Cd batteries to Li-ion batteries of size 18650. At first glance, there is nothing complicated about this. You remove the old Ni-Cd batteries from the case and install new Li-ion ones. But it turned out that not everything is so simple. The following describes what you should pay attention to when upgrading your cordless tool.

For the remodel you will need:

I'll start with 18650 lithium-ion batteries. Purchased at.

The nominal voltage of the elements is 18650 - 3.7 V. According to the seller, the capacity is 2600 mAh, marking ICR18650 26F, dimensions 18 by 65 mm.

The advantages of Li-ion batteries over Ni-Cd are smaller dimensions and weight, with a higher capacity, as well as the absence of the so-called “memory effect”. But lithium-ion batteries have serious disadvantages, namely:

1. Negative temperatures sharply reduce capacity, which cannot be said about nickel-cadmium batteries. Hence the conclusion - if the tool is often used at subzero temperatures, then replacing it with Li-ion will not solve the problem.

2. Discharge below 2.9 - 2.5V and overcharge above 4.2V can be critical, and complete failure is possible. Therefore, a BMS board is needed to control charge and discharge; if it is not installed, the new batteries will quickly fail.

The Internet mainly describes how to convert a 14-volt screwdriver - it is ideal for modernization. With four 18650 cells connected in series and a nominal voltage of 3.7V. we get 14.8V. - just what you need, even with a full charge plus another 2V, this is not dangerous for the electric motor. What about a 12V instrument? There are two options: install 3 or 4 18650 elements, if three then seem to be not enough, especially with partial discharge, and if four - a bit too much. I chose four and in my opinion I made the right choice.

And now about the BMS board, it is also from AliExpress.

This is the so-called battery charge and discharge control board, specifically in my case CF-4S30A-A. As you can see from the markings, it is designed for a battery of four 18650 “cans” and a discharge current of up to 30A. It also has a built-in so-called “balancer”, which controls the charge of each element separately and eliminates uneven charging. For proper operation The batteries for assembly are taken from the same capacity and preferably from the same batch.

In general, there are a great variety of BMS boards on sale with different characteristics. I don’t recommend taking it for a current lower than 30A - the board will constantly go into protection and to restore operation, some boards need to be briefly supplied with charging current, and to do this you need to remove the battery and connect it to a charger. The board we are considering does not have such a drawback; you just release the trigger of the screwdriver and in the absence of short circuit currents, the board will turn on itself.

The original universal charger was perfect for charging the converted battery. In recent years, Interskol has begun to equip its tools with universal chargers.

The photo shows to what voltage the BMS board charges my battery together with the standard one. charger. The voltage on the battery after charging is 14.95V, slightly higher than that required for a 12-volt screwdriver, but this is probably even better. My old screwdriver became faster and more powerful, and the fears that it would burn out gradually dissipated after four months of use. That seems to be all the main nuances, you can start remaking.

We disassemble the old battery.

We solder the old cans and leave the terminals along with the temperature sensor. If you also remove the sensor, it will not turn on when using the standard charger.

According to the diagram in the photo, we solder 18650 cells into one battery. The jumpers between the “banks” must be made with a thick wire of at least 2.5 square meters. mm, since the currents when operating a screwdriver are large, and with a small cross-section, the power of the tool will sharply drop. They write online that Li-ion batteries cannot be soldered because they are afraid of overheating, and they recommend connecting them using spot welding. You can only solder by needing a soldering iron with at least 60 watts of power. The most important thing is to solder quickly so as not to overheat the element itself.

It should be approximately so that it fits into the battery case.

“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 technical specifications for each specific battery). Exceeding these values ​​may damage the battery and render it inoperable. For Li-Ion protection The battery uses special charge-discharge controllers 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 is 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 excellent 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 " throughput"protection board. That is, a 4A controller is designed for a current of 4A and at 8A it will have overload protection. A 16A rated load controller will "go into protection" at 30±10A. All these parameters are indicated on the "Characteristics" tab " for each specific model controller.

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

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 most optimal 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), power supplies 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've already written a couple small 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. Anyone interested can check out model range.
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.

Well, what should those who have an old instrument do? Yes, everything is very simple: throw away the Ni-Cd cans and replace them with Li-Ion of the popular 18650 format (the marking indicates a diameter of 18 mm and a length of 65 mm).

What board is needed and what elements are needed to convert a screwdriver to lithium-ion

So, here is my 9.6 V battery with a capacity of 1.3 Ah. At maximum charge level it has a voltage of 10.8 volts. Lithium-ion cells have a nominal voltage of 3.6 volts, a maximum voltage of 4.2. Therefore, to replace the old nickel-cadmium cells with lithium-ion ones, I will need 3 elements, their operating voltage will be 10.8 volts, maximum - 12.6 volts. Exceeding the rated voltage will not harm the motor in any way, it will not burn out, and with a larger difference, there is no need to worry.

Lithium-ion cells, as everyone has long known, categorically do not like overcharging (voltage above 4.2 V) and excessive discharge (below 2.5 V). When the operating range is exceeded in this way, the element degrades very quickly. Therefore, lithium-ion cells always work in tandem with electronic board(BMS – Battery Management System), control element and controlling both the upper and lower voltage limits. This is a protection board that simply disconnects the can from the electrical circuit when the voltage goes beyond the operating range. Therefore, in addition to the elements themselves, such a BMS board will be required.

Now there are two important points that I experimented with unsuccessfully several times until I came to the right choice. This is the maximum permissible operating current of the Li-Ion elements themselves and the maximum operating current of the BMS board.

In a screwdriver, the operating currents at high loads reach 10-20 A. Therefore, you need to buy elements that are capable of delivering high currents. Personally, I successfully use 30-amp 18650 cells manufactured by Sony VTC4 (capacity 2100 mAh) and 20-amp Sanyo UR18650NSX (capacity 2600 mAh). They work fine in my screwdrivers. But, for example, the Chinese TrustFire 2500 mAh and the Japanese light green Panasonic NCR18650B 3400 mAh are not suitable, they are not designed for such currents. Therefore, there is no need to chase the capacity of the elements - even 2100 mAh is more than enough; the main thing when choosing is not to miscalculate the maximum permissible current discharge.

And in the same way, the BMS board must be designed for high operating currents. I saw on Youtube how people assemble batteries on 5 or 10-amp boards - I don’t know, personally, such boards immediately went into protection when I turned on the screwdriver. In my opinion, this is a waste of money. I will say this, that Makita itself puts 30-amp circuit boards in its batteries. That's why I use 25 amp BMS purchased from Aliexpress. They cost about 6-7 dollars and are searched for “BMS 25A”. Since you need a board for an assembly of 3 elements, you need to look for a board with “3S” in its name.

Another important point: some boards may have different contacts for charging (designated “C”) and load (designated “P”). For example, the board may have three contacts: “P-”, “P+” and “C-”, like on a native Makita lithium-ion board. Such a fee will not suit us. Charging and discharging (charge/discharge) must be carried out through one contact! That is, there should be 2 working contacts on the board: just “plus” and just “minus”. Because our old charger also only has two pins.

In general, as you might have guessed, with my experiments I wasted a lot of money on both the wrong elements and the wrong boards, making all the mistakes that could be made. But I gained invaluable experience.

How to disassemble a screwdriver battery

How to disassemble an old battery? There are batteries where the case halves are attached with screws, but there are also ones with glue. My batteries are just one of the last ones, and I generally for a long time believed that they were impossible to disassemble. It turns out it's possible if you have a hammer.

In general, with the help of intensive blows to the perimeter of the edge of the lower part of the case (a hammer with a nylon head, the battery must be held suspended in your hand), the gluing area is successfully separated. The case is not damaged in any way, I have already disassembled 4 pieces like this.

The part that interests us.

From the old circuit, only contact plates are needed. They are firmly spot welded to the top two elements. You can pick out the weld with a screwdriver or pliers, but you need to pick as carefully as possible so as not to break the plastic.

Everything is almost ready for further work. By the way, I left the standard temperature sensor and circuit breaker, although they are no longer particularly relevant.

But it is very likely that the presence of these elements is necessary for the normal operation of the standard charger. Therefore, I strongly recommend saving them.

Assembling a lithium-ion battery

Here are the new Sanyo UR18650NSX cells (you can find them on Aliexpress using this article number) with a capacity of 2600 mAh. For comparison, the old battery had a capacity of only 1300 mAh, half as much.

You need to solder the wires to the elements. Wires must be taken with a cross-section of at least 0.75 sq. mm, because we will have considerable currents. A wire with this cross-section works normally with currents of more than 20 A at a voltage of 12 V. Lithium-ion cans can be soldered; short-term overheating will not harm them in any way, this has been verified. But you need a good fast-acting flux. I use TAGS glycerin flux. Half a second - and everything is ready.

Solder the other ends of the wires to the board according to the diagram.

I always use even thicker wires of 1.5 sq. mm for the battery contact connectors - because space allows. Before soldering them to the mating contacts, I put a piece of heat-shrink tubing on the board. It is necessary for additional isolation of the board from the battery cells. Otherwise, the sharp solder edges can easily rub or pierce the thin film of the lithium-ion cell and cause a short circuit. You don’t have to use heat shrink, but at least laying something insulating between the board and the elements is absolutely necessary.

Now everything is insulated as it should.

The contact part can be strengthened in the battery case with a couple of drops of super glue.

The battery is ready for assembly.

It’s good when the case is on screws, but this is not my case, so I just glue the halves together again with “Moment”.

The battery is charged using a standard charger. True, the operating algorithm is changing.

I have two chargers: DC9710 and DC1414 T. And they work differently now, so I'll tell you exactly how.

Makita DC9710 charger and lithium-ion battery

Previously, the battery charge was controlled by the device itself. When the full level was reached, it stopped the process and signaled the completion of charging with a green indicator. But now the BMS circuit we installed is responsible for level control and power shutdown. Therefore, when charging is complete, the red LED on the charger will simply turn off.

If you have such an old device, you are in luck. Because everything is simple with him. The diode is on - charging is in progress. Goes off – charging is complete, the battery is fully charged.

Makita DC1414 T charger and lithium-ion battery

There is a small nuance here that you need to know. This charger is newer and is designed to charge a wider range of batteries from 7.2 to 14.4 V. The charging process on it proceeds as usual, the red LED is on:

But when the battery (which in the case of NiMH cells is supposed to have a maximum voltage of 10.8 V) reaches 12 volts (we have Li-Ion cells, for which the maximum total voltage can be 12.6 V), the charger will go crazy. Because he will not understand which battery he is charging: either a 9.6-volt one or a 14.4-volt one. And at this moment, the Makita DC1414 will enter error mode, flashing the red and green LED alternately.

This is fine! Your new battery will still charge - although not completely. The voltage will be approximately 12 volts.

That is, you will miss some part of the capacity with this charger, but it seems to me that this can be survived.

In total, upgrading the battery cost about 1000 rubles. The new Makita PA09 costs twice as much. Moreover, we ended up with twice the capacity, and further repairs (in the event of a short-term failure) will only consist of replacing lithium-ion elements.

Converting a screwdriver battery to lithium cells

Many owners of screwdrivers want to convert their batteries to lithium battery cells. Many articles have been written on this topic, and in this material I would like to summarize the information on this issue. First of all, let's look at the arguments in favor of converting a screwdriver to lithium batteries and against it. We will also consider individual aspects of the battery replacement process itself.

First you need to think, do I need this alteration? After all, this will be an outright “homemade” and in some cases can lead to failure of both the battery and the screwdriver itself. Therefore, let's look at the pros and cons of this procedure. It is possible that after this some of you will decide to abandon the conversion of Ni─Cd to lithium cells.

Pros

Let's start with the advantages:

• The energy density of lithium-ion elements is significantly higher than that of nickel-cadmium elements, which are used by default in screwdrivers. That is, a lithium battery will have less weight than a cadmium battery with the same capacity and output voltage;
• Charging of lithium battery cells occurs much faster than in the case of Ni─Cd. It will take about an hour to charge them safely;
• Lithium-ion batteries do not have a “memory effect”. This means that they do not need to be completely discharged before charging..

Now about the shortcomings and difficulties.

Cons

• Lithium battery cells cannot be charged above 4.2 volts and discharged below 2.7 volts. In real conditions, this interval is even narrower. If you go beyond these limits, the battery can be damaged. Therefore, in addition to the lithium cans themselves, you will need to connect and install a charge-discharge controller in the screwdriver;
• The voltage of one Li─Ion element is 3.6─3.7 volts, and for Ni─Cd and Ni─MH this value is 1.2 volts. That is, problems arise with assembling a battery for screwdrivers with a voltage rating of 12 volts. From three lithium cans connected in series, you can assemble a battery with a nominal value of 11.1 volts. Out of four ─ 14.8, out of five ─ 18.5 volts and so on. Naturally, the voltage limits during charge-discharge will also be different. That is, there may be problems with the compatibility of the converted battery with the screwdriver;
• In most cases, 18650 standard banks are used as lithium cells for conversion. They differ in size from Ni─Cd and Ni─MH cans. In addition, you will need a place for the charge-discharge controller and wires. All this will need to fit into a standard screwdriver battery case. Otherwise, it will be extremely inconvenient for them to work;
• A charger for cadmium batteries may not be suitable for charging the battery after it has been rebuilt. It may be necessary to modify the charger or use universal chargers;
• Lithium batteries lose their functionality at low temperatures. This is critical for those who use a screwdriver outdoors;
• The price of lithium batteries is higher than cadmium batteries.

Replacing batteries in a screwdriver with lithium ones

What do you need to consider before starting work?

You need to decide on the number of elements in the battery, which ultimately decides the voltage value. For three elements the ceiling will be 12.6, and for four ─ 16.8 volts. We are talking about converting widely used batteries with a nominal value of 14.4 volts. It is better to choose 4 elements, since during operation the voltage will drop quite quickly to 14.8. A difference of a few volts will not affect the operation of the screwdriver.

In addition, more lithium cells will give greater capacity. This means more operating time for the screwdriver.

Next, you need to choose the right lithium cells themselves. The form factor without options is 18650. The main thing you need to look at is the discharge current and capacity. According to statistics, during normal operation of a screwdriver, the current consumption is in the range of 5-10 amperes. If you press the start button sharply, the current may jump to 25 amperes for a few seconds. That is, you need to choose lithium ones with a maximum discharge current of 20-30 amperes. Then, with a short-term increase in current to these values, the battery will not be damaged.

The nominal voltage of lithium cells is 3.6-3.7 volts, and the capacity in most cases is 2000-3000 mAh. If the battery case allows, you can take not 4, but 8 cells. Connect them two by two into 4 parallel assemblies, and then connect them in series. As a result, you can increase the battery capacity. But not every case will be able to pack 8 cans of 18650.

And the last preparatory stage is the choice of controller. According to its characteristics, it must correspond to the rated voltage and discharge current. That is, if you decide to assemble a 14.4 volt battery, then choose a controller with this voltage. The operating discharge current is usually selected to be two times less than the maximum permissible current.

Above, we established that the maximum permissible short-term discharge current for lithium cells is 25-30 amperes. This means that the charge-discharge controller should be designed for 12-15 amperes. Then the protection will operate when the current increases to 25-30 amperes. Don't forget also about the dimensions of the protection board. It, along with the elements, will need to be placed in the battery case of the screwdriver.