Restoring a screwdriver battery. Repairing or restoring a screwdriver battery How to repair a lithium battery for a screwdriver

Let me start with the fact that there are a lot of videos on the Internet on restoring batteries from screwdrivers, and they are all the same as a mirror, short description The recovery process that these people propose is that we take the battery, push it with a power supply or another battery, then charge it and use it, and it’s strange that no one looks at what voltage will be on it when it sits for a week or two. I propose a completely different way of recovery

Which doesn’t just charge and use until the battery dies again. And this is what you did and use it as a new battery until the need arises. This method was filmed in a rough version about a month ago, but I never dared to post it on the site, I just didn’t want to re-shoot it for a more correct explanation. And to be honest, I don’t have time Lately very little free.

But time has passed, which has shown that the recovery option that many people on the network suggest using is not destined to survive for more than a certain period of time. And my version, even after 2-1 months of inactivity, as if nothing had happened, quietly works and charges, I still tried to shoot new video a video where I’ll try to tell you everything in a nutshell.

In fact, everything turned out to be very simple, and the NI-CAD 1.2V battery I disassembled helped me with this, which showed me that even with all zeros on the outside of the device, inside the patient is more alive than dead and feels very good.

An attempt to regenerate the tire relative to the slip plate was made using distilled water, and the process was quite successful, as a result of which I came up with the easiest way to restore them even without disassembling the batteries!

It is enough to drill a hole in the battery in the place behind the rolling +, and pour 20-40 ml of distilled water into it. After a couple of cycles, cover the hole lightly with silicone.

If you are not sure or are afraid of ruining a damaged battery, you can do this with one battery as an example.

If your batteries have voltage and it is within the operating range, then you may have a problem with the following:

- charger faulty

— the thermal protection of the battery pack worked

— in the battery pack there is one battery drained to 0 Volts.

Also, if you notice that the drill has begun to work somewhat sluggishly and at the same time works for the same long time after charging, then you most likely have a problem in one or more batteries that are at zero!

Repairing screwdriver batteries with your own hands is a very real task, although somewhat labor-intensive. Before starting work, it is planned to carry out high-quality diagnostics of the device, because it is not always possible to clarify and specify the breakdown immediately. In this way it is possible to identify fault locations and take right decisions for repair or replacement of elements. It is worth noting that several faults can be detected at the same time and all of them must be eliminated by restoration or replacement, therefore there is no need to delay resolving this issue.

What is a cordless screwdriver?

A cordless screwdriver is a tool designed for screwing in bolts, screws, self-tapping screws and other elements necessary to provide fixed fasteners. In addition, with the help of this unit you can carry out drilling work on surfaces made of metal, brick, wood and plastic.

Screwdrivers belong to the category necessary tools, which should be in the arsenal of both professional builders and home craftsmen. One of the most popular elements for a tool is a battery such as a battery for a Makita screwdriver. The quality of the battery for the Interskol screwdriver is not inferior to it.

What causes self-reproduction of battery repair

The price of the tool is based on the cost of factory-assembled elements, 70% of which is the battery, which is essentially the most expensive part of it. This structure must be handled carefully, strictly adhering to the prescribed instructions and taking breaks between work.

However, as practice shows, when breakdowns occur regarding the battery, technicians often wonder what to do in such a situation? Either repair the tool or buy a new screwdriver, because replacing the battery will not be cheap. However, it is worth considering such an option as repairing screwdriver batteries yourself.

It turns out that if you set such a goal, then it is quite possible to put the tool in order and continue to use it successfully without spending extra money. There is no doubt that you will have to tinker a little and delve into all the intricacies, but the result is worth it.

Types of batteries for cordless screwdrivers

In order to reproduce the repair of screwdriver batteries with your own hands, you need to have an idea of ​​the types of batteries. All screwdrivers, regardless of their brand and manufacturer, are identical in structure.

The structure of a screwdriver battery can be understood if you disassemble its unit, which consists of several elements assembled in a certain sequence. The provision of electricity at the moment is carried out by different basic elements that differ significantly from each other.

Among the batteries are:

Nickel-cadmium;
nickel metal hydride;
lithium-ion.

Characteristics of batteries and the possibility of their “reanimation”

Lithium-ion battery cells for screwdriver repair are of the highest quality and have a long service life. However, they do not have a memory effect, and their only drawback is the inability to function when sub-zero temperature. However, as practice shows, manufacturers simply try not to advertise the negative aspects of their products. For example, lithium, as it expires service life tends to decompose, and unfortunately nothing can be done about it.

As for nickel-cadmium batteries, they dry out after a certain period of time. But here, unlike lithium-ion cells, with the proper attitude and the right approach to their “reanimation”, there is the possibility of refilling. And if the banks were affected by the memory effect, then, according to electricians, they need to be reflashed. However, these processes are painstaking and long, so most often the issue is resolved by completely replacing the elements.

Well, if we start talking about repairs regarding nickel-metal hydride batteries, then unfortunately there is no other option other than replacing them.

Charging the screwdriver battery

It goes without saying that if by repairing a cordless screwdriver we mean repairing the battery, then in this situation, every structure without exception is subject to restoration. Today it is possible to buy lithium-ion, nickel-metal hydride, and nickel cadmium batteries for a relatively low price. Installing them yourself involves disassembling and assembling the battery and replacing the filling, which in principle should not cause any particular difficulties.

Carrying out fault diagnosis

The first step is to disassemble the battery and accurately determine the location of the fault. The entire circuit will be non-functional if at least one element is damaged. A faulty one is determined using a multimeter and a 12-volt lamp. To do this, the battery is charged until it is completely charged.

Next, the housing is disassembled and the voltage is determined. It should be measured in each element of the circuit. If “cans” with performance below the nominal value are detected, they are marked, after which the battery must be assembled and put into operation until the power drops.

Then the structure is disassembled again and the voltage of the elements is measured again. In the marked subsidence areas, the stress is monitored more clearly. The presence of a difference in different elements, starting from 0.5 V, indicates their imminent failure, even if they continue to work for some time.

Possibility of restoring the battery capacity of a screwdriver by flashing nickel-cadmium batteries

Repairing screwdriver batteries in this way with your own hands can only be suitable when the batteries are not subject to drying out. If this does happen, then unfortunately, we can state that they cannot be restored, and there is nothing left to do except send them to a landfill. It is possible to verify the state of the electrolyte in the cells only by practical means: if the method does not work, then they are dry. If it works, then everything is in order, very soon you will be able to use the screwdriver as usual. Charging of the screwdriver elements is carried out using high current and voltage.

The procedure for restoring the battery using flashing

The entire flashing process is as follows:

The battery is disassembled;
the charging of all elements included in its composition is checked, without exception;
then a high-power charger is connected to the batteries and adjusted accordingly to ensure that each cell is supplied with a voltage of approximately 3.6 V.
Charging of the screwdriver battery is reproduced with a short-term current supply: 5 seconds;
then the result is checked by measuring the voltage readings with a multimeter. If these numbers in each charged element reach the limit of 1.5 volts or higher, then everything went well;
After control, the battery is assembled and used as usual.

This method allows you to neutralize the memory effect of nickel-cadmium batteries. If charging fails, the cells are desoldered and disposed of. The only option in this situation is to install new batteries in place of the damaged ones.

Identifying and replacing used containers in a screwdriver

When deciding whether to repair a screwdriver battery, you should take into account the difficulty that arises when opening the battery. The fact is that they are almost always carefully sealed. And this is understandable, because it is profitable for manufacturers to motivate the average person to buy a new element, and not to repair it themselves. Therefore, one way or another, you will have to “sweat” a little.

If you want to carefully get to the internal contents of the battery, it is still possible, which is the main task.

The remaining steps here are quite simple, and their order is as follows:

Before starting manipulations, the 12V battery for the screwdriver is charged;
after opening the battery, the batteries are removed from it;
then the voltage on each element is checked. The readings are recorded;
the next stage in the work: connecting voltage to identify weak points;
then the voltage is measured again and those that are poorly charged are identified: they must be replaced with new ones;
items are purchased according to the labeling. If you decide to replace them in full, it will be a little more expensive, but you won’t have to worry about looking for a weak link:
all elements are soldered in a strict sequence of plus and minus, installed in the battery and resealed

What to pay attention to

The most important thing in this matter is to look at things soberly and not worry that something may not work out. However, one cannot do without taking into account the subtleties, and self-repair you will have to be as pedantic as possible. The factory technological process involves welding the plates used to connect the elements.

At home, you can only use a soldering iron. It is important to take into account that the elements should not be subjected to severe overheating, and it is necessary to know that they all must be similar in capacity and voltage output. Repairing a screwdriver battery with your own hands is not such a difficult task for good master. The main thing here is to have incentive, desire and love for this business.

Those of us who use a tool like cordless screwdriver, must remember that at some point the battery that powers it may become unusable. Moreover, in in this case we're talking about not about détente, but about the loss of her quality characteristics, as a result of which you will have to think about replacement, and this will require large expenses from the owner.

Finding yourself in such a situation, the consumer may consider purchasing a new screwdriver, which will be more simple solution problems rather than equipping old tools with new batteries. However, in such difficult situation a solution can be found. If the screwdriver uses a certain type of power supply, you can try to restore the battery.

In terms of implementation, repairing batteries for a screwdriver looks like a completely simple task, so even if you fail, it will not lead to any serious consequences or expenses for you. Next, the most important points regarding repairing a screwdriver battery with your own hands will be covered in detail.

Do-it-yourself screwdriver battery repair: which batteries can be repaired

As a power source in models of screwdrivers produced today One of the following battery types can be used:

• nickel-cadmium batteries;
• nickel metal hydride batteries;
• lithium-ion batteries.

Moreover, each of these power sources has its own characteristics.

Lithium-ion

If we evaluate these batteries based on characteristics such as workmanship and service life, then lithium-ion batteries are beyond competition. Due to their lack of memory effect, they can be considered practically ideal option of such a power source, however, it is necessary to mention that they have such a disadvantage as the impossibility of their operation at subzero temperatures.

This is precisely the statement made by the manufacturers of such batteries, although in reality they have other Negative consequences. For example, when such a battery loses its service life, lithium decomposes in them, and this reaction cannot be affected by any influence.

Nickel-cadmium

These batteries are different from the previous ones in that the moment they reach the end of their shelf life, they dry out. Therefore, those owners who know how to deal with such batteries in such a condition, they are just re-uploaded. However, this is not so easy to do, and therefore there are very few people who decide to take such a step.

After all, there is a less expensive solution to the problem, which is to place new cans for the screwdriver battery in the battery. In some situations, when the cause of the problem is the memory effect, which is usually considered one of the significant disadvantages of nickel-cadmium electrical capacitors, you can solve the problem of restoring their functionality by flashing it.

Nickel metal hydride

As for nickel-metal hydride batteries, nothing can be done about them when they use up their service life. In such situations, home handyman There is only one way out - to look for a replacement for this battery.

If, when a screwdriver battery fails, we consider replacing the power source, then such a solution will be appropriate regardless of the type of battery the screwdriver is equipped with. Currently, you can find many stores online that offer every user to buy quite affordable prices battery of any type, including lithium-ion, nickel-cadmium power supplies. True, in this case the buyer will have to be prepared for the fact that he will have to install this power source himself.

First you will have to disassemble the battery constituent elements, replace the failed one with a working filling, after which The assembly process is performed in reverse order. It is this procedure that will be given further attention, but first it will be useful to consider the operation of restoring nickel-cadmium batteries.

How to restore the battery capacity of a screwdriver: flashing nickel-cadmium batteries

It makes sense to use this method only when the most unpleasant thing has not yet happened to the power source - it has dried out. If all the signs of this phenomenon are present, then all that remains is to throw it away. Understand, What is the state of the electrolysis of such batteries?, you can conduct the following experiment with them: if after charging they also do not show signs of life, then we can conclude that the elements are dry.

If you managed to restore the battery's functionality, then this will be a great success for you. If we talk in more detail about the technology for solving this issue, then restoring a screwdriver battery involves influencing its elements using current and voltage of a significant value.

Sometimes, after repeated charging of certain elements, the desired result cannot be achieved. In this case, all you have to do is throw them away. We will have to replace the elements that have become unusable with working batteries. I would like to repeat once again that the described method is effective in combating the memory effect that nickel-cadmium batteries have. If the battery has exhausted its resource, then this method will be ineffective.

Replacing the battery in a screwdriver: identifying and changing used containers

The most common difficulties that arise when repairing a screwdriver battery are the following: it is important to open the batteries in such a way as not to damage them.

As a rule, manufacturers provide this possibility, and therefore trying to seal their batteries tightly in order to avoid situations in which craftsmen try to repair the screwdriver battery on their own. Thus, they force owners to abandon such an idea and force them to visit the store to buy a new battery.

In principle, this is not surprising, because companies pursue their own goals. However, in this case, a solution can be found. But you should immediately be prepared for the fact that repairs will take some time. However, if you are willing to spend your personal hours on such work, this means that by following all the recommendations, you will achieve your goal and be satisfied with the operations performed.

In the process of performing this work, you should be aware of certain nuances - without them it will be difficult for you to correctly assemble the elements into a single battery. During factory assembly, the plates used to connect the elements are not soldered. For these purposes, spot welding is used. Since you do not have such an opportunity, you will have to spend time on soldering, using a regular soldering iron.

While performing this operation, keep in mind that the state of the elements severe overheating may have a negative impact, which should not be allowed. Also important point It is also important that each element has the same capacity, as well as the output voltage.

You should also take a closer look at overclocking the new battery. It is necessary to resort to this procedure when you have already been able to reflash the old elements. A similar procedure is recommended for nickel-cadmium batteries, which should be carried out every 6 months. The main thing this procedure allows you to achieve is to ensure maximum charging of the battery and subsequent complete discharge. This work must be done in two steps, or even better, in three.

The condition of most nickel-cadmium batteries is negatively affected by repeated charging without prior discharging. If you ignore this recommendation, then this may cause memory effect. Its essence can be described as follows: the place from which they began to charge them begins to be considered as a starting point.

Conclusion

If, while using a screwdriver, you find that its battery has exhausted its entire working life, then you should not prepare to buy a new device. If you find yourself in a similar situation, you can try to restore its functionality. There are many ways to estimate the chances successful repair, after which you can begin to implement the plan. In some situations, this approach allows you to save a lot of money and continue to perform the necessary operations on the same day.

And needs replacing. Buying a new one is often difficult, and if you succeed, it is at a very high price. That's why they say it's easier to buy new tool, or repair the screwdriver battery yourself.

On the Internet there is a large number of videos in which electronics enthusiasts clearly show how to repair a screwdriver battery with their own hands. If you are seriously concerned about the issue, think about saving Money and whether it is possible to repair a screwdriver battery with your own hands, watching such videos can be a good start for repairing the battery yourself in the future.

How to disassemble the battery

Battery packs home tool their design is almost identical to each other, regardless of the model of the tool (Bosch, Makita, Hitachi). They are packaged in a plastic case consisting of two parts. The number of batteries may vary depending on the output voltage of the tool used. All elements are soldered in a certain sequence. The lead ends or terminals at which the battery voltage is usually measured are brought out.

Most screwdriver or drill battery packs are designed so that they are very easy to disassemble, regardless of whether we are repairing the battery of an Interskol screwdriver or another model. Several mounting screws need to be removed using a regular screwdriver. There are batteries that are difficult to disassemble, but can be removed with a screwdriver and a pocket knife. The adhesive layer is removed with a knife, and the two mating surfaces are moved apart with a sharp self-tapping screw.

The difference between screwdriver batteries and each other may lie in the presence or absence of a temperature sensor, which automatically turns off the battery under critical heating conditions (above 50°C). The sensor constantly monitors the temperature not only under load, but also under the conditions of the current battery charge. The controller reads all the data and processes it, “remembers” the capacity and other indicators. As soon as the capacity reaches 80-90% and the voltage reaches 14 V, the control unit turns everything off. Such batteries last for years without losing their technical characteristics.

The market offers a large number inexpensive models screwdrivers.
Cheaper devices do not have these technical devices, and you need to monitor all processes yourself.

Types of battery repairs

How to reanimate a screwdriver battery? There are three ways:

• express battery repair using zapping method ;
• replacing individual elements in the battery ;
• replacement of all elements of the battery pack .

Express repair of nickel-cadmium batteries using zapping method

In English it means to burn, applying short pulses of high current over a period of several seconds. We can say that this is a kind of emergency resuscitation of batteries. It should be noted right away that this option is quite risky, and not every battery is able to withstand such “shock therapy” with high current. It is only possible to use high current if the screwdriver has nickel-cadmium batteries installed. Other batteries ( , ) cannot be subjected to such effects.

The essence of purging is to destroy the crystals formed inside nickel-cadmium batteries with high current. These crystals are called dendrites, and due to their growth, the battery capacity gradually decreases. “Pumping” with high currents quickly destroys the formed crystals and sharply reduces the self-discharge of the battery.

It is stated that zapping can be effective for any NiСd, even if they are completely discharged to zero or have been lying unused for 10 or 20 years. The question is always about the likelihood of successful repair in such “difficult” cases - when batteries are “repaired” in this way, it will either be successful or not. However, it doesn't hurt to try to revive them. Of course, while maintaining maximum caution.

To carry out zapping you will need:

• any high current charger ;
• multimeter to monitor voltage ;
• welding machine ;
• crocodile clip ;
• zapping electrode ;
• protective equipment .

You should not use a regular power supply as a charger. Even if the current strength of such chargers is 10-15 A, they will not withstand high voltage. Using a double-sided clamp, tight contact is ensured on one terminal, and the electrode itself will be held on the other terminal. It is impossible to hold it with your fingers: during burning it will become hot. A zapping electrode is a piece of wire that is rolled into a tight bundle (there is no insulation). Its cross-section is maximum 1.5 mm 2, and its length is 6-7 cm.

Instead of higher quality welding machine Especially daring electronics enthusiasts repair batteries using a regular soldering iron. But a spot soldering tool will be preferable for repairs. Protective equipment (robe, goggles, special non-flammable substrate) is necessary because sparks always appear during high current blowing.

Work progress

It is better to blow through each battery separately, the algorithm is as follows:

• Attach the electrode with a minus sign to its minus pole. Do not confuse the polarity, an important point.
• “Blow out” the positive electrode with short pokes, their frequency is 2-3 times per second . Typically, for a can with an output voltage of 1.2 V, blowing must be done for 3-4 seconds with a frequency of 2-3 small pokes per second;
• Measure voltage readings after the first stage . It should be raised to a maximum of 1.3 V. If the voltage is higher, the time of pokes or their number should be reduced.

You need to poke very quickly and carefully, not allowing the electrode to weld even for a short time to the pole of the Ni Cd battery of the screwdriver, in order to avoid completely burning the battery. It is recommended to put a protective intermediate electrode on the positive electrode, or to hook on an alligator clip to protect the surface of the battery pole.

The procedure is repeated up to 25 times until the battery capacity is restored. During the entire process, it is necessary to constantly monitor the temperature of the batteries. The intervals between zappings should be at least 15 minutes. Only in this case will the reanimated battery have a chance to extend its service life.

Replacing individual elements in the battery

If the battery capacity drops, it means that at least several of its elements have failed. All batteries cannot die at once, so first you need to find the lowest-capacity batteries in the chain, and then disassemble the battery and replace them with new ones.

New batteries can be ordered from any online store. At the same time, it is important to buy those elements whose type and capacity fully correspond to the previous ones. If the screwdriver is nickel-cadmium batteries, then it’s worth purchasing the same ones, with a similar level of capacity. If you can get the same battery, you can remove the most capacious elements from it and put it in the one that is being repaired.

How to identify “weak links”

Searching for dead batteries in a circuit can be done in two ways:

• using a multimeter ;
.

For the first method, you only need a multimeter:

• charge the battery completely ;
• disassemble the battery case ;
• measure the nominal U on each battery (rated for nickel-cadmium batteries - 1.2 V, for lithium-ion batteries - 3.6 V);
• mark with a cross the elements where U is below nominal so as not to be confused with others;
• assemble the battery ;
• turn on the screwdriver ;
• work until there is a noticeable reduction in power ;
• disassemble the battery again, measure the U values ​​again .

On batteries marked with a cross, the “dips” in voltage will be significantly greater than with others - most often below 1 V. As for the difference between the U values ​​in the battery, if it is at least 0.5-0.7 V, this is quite significant.

The second method of finding dead batteries is less labor-intensive and simpler. If the screwdriver output voltage is 12 V, you will need a lamp with the same output voltage.

Procedure:

• charge the battery completely ;
• connect the lamp as a load to both poles of the battery ;
• wait until the battery is completely discharged ;
• use a multimeter to measure the voltage readings at the terminals of all elements one by one .

“Dead” batteries are easy to separate because their voltage drops the most after discharge.

Repair

So, the failed elements have been found, new ones have been purchased, and now you can proceed directly to repairing the battery.

To repair the battery you will need:

• soldering iron;
• low corrosive flux ;
• tin;
• copper plates (in case the “original” ones broke during disassembly) .

It is not necessary to use spot welding in case of partial battery repair. But during soldering you need to be careful not to overheat the elements. It is best to connect the batteries to each other using the plates that they had. If they break during disassembly of the battery into individual elements, then new plates will need to be made from copper.

Don't forget about polarity. Each battery element for a screwdriver is connected to its neighbor according to a certain sequence. The minus of one can must be connected to the plus of another, and the minus of another can must be connected to the plus of the third, and so on.

After the chain is reassembled, care must be taken to ensure that the voltage potential of all elements is equal. To do this, you should leave the batteries on charge for the whole night, then they should cool down over the next 24 hours. After this, the voltage is measured on each element. If soldering and the charging cycle were carried out correctly, then the multimeter will show approximately the same U figure on all batteries - 1.3 V.

Now you need to carry out at least two charge-discharge cycles for the battery in a natural way: place the repaired battery in a native screwdriver and work with it until it is completely discharged.

By the way: partial renovation Li-ion battery screwdriver can be done in a way that requires minimal financial costs. If the unit has 18650 batteries installed, you can actually borrow the same ones from an old non-working laptop, if possible.

Replacing all elements of the battery pack

The required number of cells can be ordered at any online store, depending on the number of old batteries. It is important to pay attention to the fact that they all initially have the same capacity.

You can completely replace all elements of the battery pack with new nickel-cadmium batteries. They are much cheaper than nickel-metal hydride batteries, and, compared to other batteries, they are the most durable and hardy. However, recently it has become increasingly common to independently convert batteries “from cadmium to lithium”, in other words, installing new lithium-ion batteries instead of old Ni-Cd.

Despite their reliability, nickel-cadmium batteries can quickly fail because they have serial connection to each other without a balancing board. If the batteries are from the same production batch, their parameters will still have a wide spread between them. With this connection, one element will charge faster, another slower, and the third may overcharge.

To make a complete switch from nickel-cadmium to lithium-ion, you will need:

• number of elements equal to the number of previous ones (with the same capacity);
• balancing board 5S (its amperage depends on how many volts the screwdriver is designed for);
• tester or multimeter ;
• soldering iron with a good tip ;
• high quality flux and lead solder ;
• silicone wires AVG 16 ;
• heat-resistant tape and hot melt adhesive .

Before starting soldering, discharge the batteries. Remove the old batteries from the unit and release the contacts. It is better not to throw away the old temperature sensor, but to leave it as additional protection against lithium overheating.

Now the main thing is to solder the lithium correctly . Cut the wires to the required length in advance, insulated, in silicone, very thick, to avoid them melting when the lithium is heated. Use a knife to clean the battery pads for soldering.

It’s good to heat the soldering iron to 300°C and start soldering using flux and lead solder. There must be flux good quality, indelible, non-conductive. Do not use acidic fluxes under any circumstances. Soldering should not take more than 2 seconds to avoid overheating of the lithium. In order for the heat to escape faster, after soldering, you can attach any iron object to the battery that absorbs heat.

Allow the batteries to cool and connect the positives and negatives as usual. Check the overall voltage. Its indicator should be on average 20.7 V if there are 15 elements.

After measuring the voltage, the board is connected. All its wiring must be laid with special gaskets so that nothing “shorts” during operation. The entire battery pack is sealed with heat-resistant tape designed specifically to insulate batteries and their contacts.

The wires and connector are soldered. If the contacts are “dangling”, they can be attached to hot glue. Now, finally, you can finally assemble the screwdriver battery pack and check its operation.

Sometimes it seems like repairing the battery Hitachi screwdriver(or another tool) is very difficult. But if you look into general principles, such as the basics of electronics from the inside, and the main principles of proper soldering, it becomes clear how to repair a battery for a screwdriver yourself. This will not only save financial resources, but will also contribute to the acquisition of valuable and useful skills.

One day, when I took my screwdriver out of the closet, I discovered that it didn’t work. The batteries were dead, the first thing I thought was and put the screwdriver on charge. But as soon as I connected the charger to the battery, it immediately showed the full charge of the battery. I connected a tester to check charging and it turned out that the batteries had high resistance, which meant they were failing.

After browsing the forums, I found out that the problem of failure of nickel-cadmium batteries used in screwdrivers is by no means new, but rather very common. In general, in addition to being cheap, these batteries are a plus for the manufacturer; they have a lot of shortcomings that become apparent during operation. This is small life cycle, and low capacity, and short battery life.
All forum members who are faced with a similar problem without hesitation boldly change nickel-cadmium batteries to lithium-ion ones, which is what I will do as well. They may be more expensive, but the screwdriver will work much longer and harder.
Without hesitation, I purchased. Since my screwdriver is 18-volt, and one battery produces 3.7 V, therefore, I needed 5 pieces. 5x3.7=18.5 V is what you need.
I also bought battery compartments, one for two batteries, the other for three. I connected everything in series. I took out the old batteries and replaced them with new ones.

This could be the conclusion, but as it turns out, I made a terrible mistake. The fact is that lithium-ion batteries cannot under any circumstances be charged in the same way as old batteries! This is even dangerous, as they can simply explode.
How then? It's not that complicated - you need a charging controller for lithium-ion batteries.
Lithium-ion batteries are very sensitive to overcharging and being discharged below normal - all these factors quickly damage them. This is perhaps their main disadvantage. But it’s easy to get rid of it by using a controller that will take over all the functions of monitoring and limiting dangerous modes and make the operation of the battery at a high-quality level.
Purchase links:

• or specifically - .

Charging controller connection diagram

The batteries are also connected in series, except that each connection between the batteries is connected to the controller. As a result of this, the controller monitors the condition of each battery and prevents it from overcharging in the circuit.
I put together a diagram. Everything works perfectly.

Check video

Screwdriver battery assembly

Since the controller was added, from battery compartments I had to refuse because there was a catastrophic lack of space. Well, this is for the better, since the screwdriver is subject to vibration, and not tight contact could not have a very good effect in the future...
I decided to solder the batteries together. In general, lithium-ion batteries are very afraid of overheating and need to be connected resistance welding. But I don't have it. So I soldered everything with a soldering iron. If you do this, then teach: use only a powerful soldering iron of 40-60 watts. Solder with acid or active flux. And under no circumstances solder one connection for more than a second. If it doesn’t work the first time, it’s better to wait five minutes and try again.
In the end I did this:

I soldered the circuit.