How to convert a cordless screwdriver to a lithium battery. How to convert a screwdriver to lithium batteries

In this article you will learn how to inexpensively convert a screwdriver battery from Ni Cd to Li Ion 18650 batteries, thereby modernizing screwdriver battery, making it more powerful and increasing battery life. All stages of the conversion are described in detail, so there should be no problems, all the necessary components are indicated and available.

Required components for conversion

For rewhitening, high-current 18650 batteries capacity 2500 mAh. Data batteries They have already welded leads for soldering, which is very convenient and, in addition, you can significantly save on battery compartments. You can order them online and are supplied in batches of 4 or 6 pieces. You can buy them using the links below:

Buy 18650 batteries - 6 pcs.

Buy 18650 batteries - 4 pcs.

Also for the conversion you will need two BMS 12.6V 40A boards, bought here:

Buy BMS board 12.6V 40A

The charger will also need to be redone and for this you will need a voltage and current stabilization module.

Video on how to remake Charger see the end of the article

Buy voltage and current stabilization

At the time of the conversion, all components (for two batteries) cost only 1,100 rubles, which is much cheaper than buying new battery for a screwdriver that will contain the same Ni Cd batteries. After looking at prices on the Internet, I discovered that one battery costs from 1200 rubles, and to remake TWO batteries, I spent only 1100! All links to components can also be found at the end of the article!

Battery conversion

The first step is to carefully disassemble the battery case and throw away the old Ni Cd batteries.

Then you need to disconnect the battery power terminal.

You need to solder two wires to it, preferably with a large cross-section; in this modification, wires with a cross-section of 4 mm² and a length of approximately 100 mm were used. In the photo above you can see the red wire, it was left in order not to confuse the polarity; it is advisable to also solder the red wire to this wire in order to avoid troubles and you will know for sure that it is +.

The shiny contact needs to be soldered negative wire:

Then you need to insert the terminal with the soldered wires back into the housing in its place, being sure to observe the polarity!

To fix the terminal, you can pour hot glue inside the glass; I haven’t found a better fixing option, especially since it holds very well!

Now you can start soldering the batteries. We remove the heat-shrink tube from the batteries and bend them so that they can be soldered in series.

Next, we apply hot melt glue to the side of the resulting battery, where the contacts stick out to the top, and glue the BMS board as shown in the photo below. Please note that the plus and minus of the board and battery are opposite each other!!!

Then we bend the battery contacts onto the board contacts and solder them, starting from the negative!

We solder a short wire to the contact of the B1 board, the other end of which we solder to the junction of the batteries!

We also solder a short wire to contact B2, the other end of which is soldered to the junction of the batteries on the opposite side!

Well, at the end, we solder the last, positive contact.

Now it remains to connect the terminals of the case with the resulting battery; to do this, solder the red wire to the “P+” contact, and the blue, negative wire to the “P-” contact.

This completes the battery conversion! All that remains is to secure the manufactured battery and put the second part of the case in place. No more than an hour of time and, as mentioned above, 1,100 rubles of money were spent on converting two batteries. After the tests, the screwdriver began to work no worse than with the factory battery and, I would say, much better in terms of power and the charge lasts longer. I advise everyone to remake their old batteries!))
Buy charger socket
Buy a soldering iron

For those who have no desire to remake the charger, you can buy a ready-made one using the link below.

Buy a ready-made charger

As you know, any battery sooner or later exhausts its life and needs either partial replacement of the batteries, or it should be changed completely. When it comes to a screwdriver, it can be much easier for someone to buy a new one than to replace the batteries in it, because this requires both time and a certain skill. However, if you have the skill and knowledge, replacing batteries in a screwdriver can be a good alternative to buying a new one. In many cases it is cheaper.

Nickel-cadmium or lithium-ion cells are usually used as batteries in screwdrivers. more unpretentious and, if a partial replacement of elements in such a block is carried out, it will still work for a long time. Partial replacement lithium batteries It can also be done, but it is a little more difficult to implement. It should be borne in mind that not only the elements themselves will have to be soldered, but also the balancing board. Also, recently, electronics enthusiasts often change screwdriver batteries with their own hands, with nicd batteries to lithium. This is a good way out if the screwdriver has to work frequently and intensively. The capacity is much higher and the number of cycles is greater.

How to repair a nickel-cadmium battery in a screwdriver

The specificity of nickel-cadmium jars is that at the end of their service life, the contents of their electrolyte can dry out. In this case, refilling with distilled water sometimes helps.

But if you think about what is better and obviously more efficient, you should still decide to replace the screwdriver batteries. Filling does not always help. There is a much higher probability that the tool will work well with a battery in which the cans will be partially replaced. Of course, provided that everything is done correctly.

Finally, the filling process itself is no less labor-intensive than the battery repair process. And if it turns out to be ineffective because the batteries are simply dry, it will be very annoying.

We disassemble the block and look for the “weak link”

Before you start with your own hands, you should keep in mind that the battery pack itself should be handled as carefully as possible. Sometimes this requires a lot of patience, because block manufacturers always strive to make it as difficult as possible to get to the batteries. This is understandable. Most manufacturers are interested in ensuring that craftsmen do not repair the screwdriver battery themselves and do not tinker with cans, but, without hesitation, purchase a new tool, often at a fairly high price.

After opening the battery, remove all batteries from its plastic case. Important point: do not forget to pre-charge the battery before carrying out this manipulation . You can charge for no more than three hours. Then, after removing the cans, you will need to use a multimeter to measure the voltage readings on each of them.

• After measuring the U of each jar, write down the results. Most likely, the elements with the lowest voltage will have to be removed later.
• Now the battery pack. You can connect a load in the form of a light bulb to it.
• Repeat the charging process again , measure the voltage on each battery and unsolder those with the weakest performance .

Of course, before replacing the batteries in a screwdriver, you should purchase new elements similar to the old ones, preferably with a small margin. Buy batteries with the same capacity.

Installing new banks

Before installing new batteries in the battery pack, it is important to take into account certain subtleties, without which it will be impossible to do everything correctly. First of all, It is important to remember to maintain polarity when soldering . And also understand the difference between conventional soldering and the principle of spot welding. Because the plates connecting the batteries to each other must be soldered in the usual way Not recommended.

If you don't have a spot welder, try using a regular soldering iron. But everything should be done clearly, carefully and as quickly as possible. The main thing is to prevent critical overheating of the batteries. Use only high quality lead solder.

By the way, it is in such cases that one of the main advantages of nickel-cadmium batteries manifests itself. Being exposed to a certain risk during repairs, they have a fairly high chance of “withstanding” high temperatures due to the strong metal body and composition, which does not have an increased explosion hazard. Lithium cells are much less resistant to flashing and are more capricious.

Place each battery in the same order as in the old bundle and reassemble the battery pack. After the battery is reassembled, you need to “swing” it properly in order to balance the potential of all elements and remove what is called the “memory effect”. Give the new battery at least two or three charge-discharge cycles. As you know, it is not recommended to constantly “recharge” nickel-cadmium batteries without first completely discharging them, which is not always possible during operation.

In the future, when using the repaired battery It is necessary to completely discharge it from time to time and then fully charge it - to prevent the frequent occurrence of the “memory effect”. It is recommended to do this at least once every six months. This way you can extend the life of nickel-cadmium cells with optimal utilization of their resources, without them accumulating unnecessary information about previous recharges.

Replacing nickel-cadmium batteries in a screwdriver with lithium ones

Recently, on forums dedicated to electrical tools, the process of replacing nickel-cadmium screwdriver batteries with Li Ion batteries is often described. And this is no coincidence. More modern Lithium based cells have much higher capacity . A they have more work cycles at least one and a half to two times.

Very often, cadmium batteries are replaced with the popular lithium 18650, so named based on their size. You can change batteries to lithium if the tool is used daily or very often. Large number of cycles lithium-ion batteries optimally suited for professional craftsmen who use the tool every day.

In order to convert a screwdriver from “cadmium to lithium”, you will need 18650 batteries and a special charging module. This module allows you to charge the battery and transfer the load on the same terminals (the same protective board that was mentioned at the beginning). Such modules have protection against short circuit between elements.

How to solder elements

Soldering is strongly recommended to be carried out exactly resistance welding machine - due to the fact that lithium batteries even more sensitive to heat than cadmium. If nickel-cadmium batteries can withstand manipulation with a soldering iron, then for lithium it is still better to use the resistance welding method.

To connect the batteries to each other you will need a thin metal strip. The strips themselves can be cut from soft tin cans. All surfaces to be joined must first be wiped with alcohol, and then begin spot welding using the device. The pulse duration is selected experimentally so that there is no burning and the connection is reliable. To ensure a reliable connection between the plate and the contact surface of the battery, it is better to make several point connections.

The excess part of the strip is cut off, and its free edge is connected to another battery. Next, all the elements are connected to each other according to the same principle. Of course, observing polarity.

The entire finished assembly is fixed to each other using electrical tape. It is better to make two turns of electrical tape on one side and two turns on the other - for greater reliability. After this, the battery contacts are connected again with a metal strip. It turns out ready new battery, to which you now need to attach the board (module).

The module can be soldered to the new battery with a regular soldering iron.

The negative wire of the battery assembly is connected to the B- terminal on the board, and the positive wire to the B+ terminal. Contact terminals are connected to terminals P- and P+, balancing taps are connected to terminals B1, B2 and B3. For solder, it is better to use high-quality flux, which spreads very well over the entire surface. The positive wire is soldered directly, and a thick wire with a cross-section of at least 0.5 mm 2 is soldered to the negative contact, since a current of at least 10 amperes will flow through it.

After this, balancing wires with a small cross-section are soldered.

• to contact B3 connect the connection point third And fourth batteries;
• to contact B2- connection point second And third;
• to contact B1- connection point first And second(we start counting from the positive contact).

After charging the battery, check the voltage on all its elements. U on each of them should not exceed 4.2 volts.

After the new battery pack is ready, we disassemble the old nickel-cadmium battery. We only remove the old batteries, and leave the old temperature sensors in place, because the screwdriver charger will not work without them. We solder a new block inside the plastic case, and fill the space remaining inside with foam plastic.

Thus, if there is a need to replace the battery in a screwdriver, you can do it yourself. In the case of old but reliable cadmium batteries, you can use the method partial replacement for new ones. And if you want to build yourself a “professional and powerful screwdriver” yourself, you can successfully completely replace the battery pack with lithium-ion cells.

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-quality is lithium batteries of the 18650 series. Structurally, they look like ordinary ones AA batteries, size is 25% larger than AA size.

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 general indicator 14.4 V. Lithium batteries should not be discharged 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.

If anyone read my previous writing, you may remember that after they gave me standard screwdriver batteries, and I urgently needed to continue working, I soldered quite powerful converter at 8 A nominal and up to 15 A short-term load. From 24 volts to 15 V. Two 7 Ah 12 V batteries were connected in series. I have a 14.4 V screwdriver.

Having trained a lot and suffered through the entire last construction season, I decided that in the new season I need normal batteries.

I scoured the Internet and realized Bosch’s marketing trick regarding my original batteries. One new battery costs the same as a new screwdriver with two batteries in the set. There was no point in buying this crap for that kind of money.

There were no lithium-ion batteries for my screwdriver model. New screwdrivers for Li-ion were of inadequate cost. Some kind of orgy of divorce of suckers.

Then the idea came to me to convert the screwdriver to lithium myself. Lithium-ion banks are 3.7 V, but we need 15–16 V. Let’s connect four batteries in series and get 16.8 V in a fully charged version (4.2 V per bank).

If you have a 12 V screwdriver, you can connect three cans in series.

Banks, that is, individual batteries from which our battery is assembled into one big battery I decided to take the 18650 type.

These are now fashionable to use in flashlights. They are also found in laptop batteries.

This is a Sony vtc4 type battery. Capable of delivering as much as 30 Amperes to the load (max). Ideal for our purpose.

Everything would be fine, but lithium is a dangerous thing, you can make a boom if you recharge it.

In addition, our individual batteries are connected in series and over time there will be a large imbalance, i.e. some banks will be recharged, while others, on the contrary, will be greatly undercharged. As a result, such a battery will quickly fail.

Our Chinese friends again came to my aid. There is such a thing called a balancer. Controls the voltage during charging on each individual bank and in case of fully charged turns it off, and the rest continue to charge, and so on until all the individual banks in our sequential battery chain are fully charged.

This thing costs the Chinese pennies. But I took it from them something a little more serious.

A little more expensive, but worth it. The fact is that these batteries have no protection. In general, I also ordered a battery controller. This thing includes the balancer discussed above, as well as a whole set of protections. In particular, it contains: short circuit protection, overheating protection, overcurrent protection, etc.

Board contacts:

• B+: battery +plus;
• B3: 1st battery -minus and 2nd battery +plus;
• B2-: 2nd battery -minus and 3rd battery +plus;
• B1-: 3rd battery -minus and 4th battery +plus;
• B: 4th battery - minus;
• P+: load/charging V+ (to screwdriver +/or to charging +);
• P-: load/charging V- (to screwdriver+/or to charging +).

Having collected everything into a single pile, I tried the screwdriver in action and nothing worked. What the hell, did the Chinese really give me bullshit, but no, they had nothing to do with it. The thing turned out to be that during the assembly process, I apparently shortened something somewhere, in general it was the protection that worked, completely disconnecting the battery from the load.

To remove the protection (guess the type yourself, this is not in the seller’s instructions) you need to apply voltage from the load side, i.e. You can simply put the battery on charge. The protection will be removed instantly.

I put everything in the standard battery case, having first removed the old nickel-cadmium cans from it. Soldered to the contact pads. To prevent them from falling out, I filled the whole thing with hot glue.

The resulting battery is charged normally by standard charging, although the voltage is not enough (18V is recommended), but I haven’t gotten around to it yet. No need to worry about recharging. The controller will automatically turn off the banks after they are fully charged.

Homemade Li-ion battery for a screwdriver it turned out to be 2.1 Ah (2100 mAh). Against the standard one with a capacity of 1.2 Ah. The new battery weighs three times less.

I tested the product while dismantling the floor formwork. Simply super, very pleased with the result. Works great, doesn't sit down for a long time, pulls powerfully.

Then I encountered a small minus. When you forget to set the force on the screwdriver (drilling mode), especially when it gets stuck, then under heavy loads stopping the engine, the protection is triggered. I don't know if this is good or not. If you also take not a balancer, but a full controller, then take a larger load for the current, otherwise you will get tired of removing the protection. Or look for a controller with auto release.

My controller has a load current of 8 A.

At first, I took the second old Akum with me, connecting to it and removing the protection. Then I made a button that switches the circuit to operating mode directly without a controller and at the same time removes the protection using the voltage of the battery itself.

• Those. You can either remove the protection by briefly pressing the button back and forth (it is latched).

• Or enable bypass mode and remove the protection at the same time.

If you want, you can buy jars for a larger capacity, but be careful in this regard, they are complete fakes. The seller from whom I took it and constantly take it has already been verified and his declared capacity corresponds to the real one.

Finally, here it is:

Happy assembly :)

The industry has been making screwdrivers for a long time, and many people have older models with nickel-cadmium and nickel-metal hydride batteries. Converting a screwdriver to lithium will improve performance characteristics device without buying a new tool. Now many companies offer services for converting screwdriver batteries, but you can do it yourself.

Benefits of lithium-ion batteries

Nickel-cadmium batteries have a low price, withstand many charging cycles, and are not afraid of low temperatures. But the battery capacity will decrease if you charge it before it is completely discharged (memory effect).

Lithium-ion batteries have the following advantages:

• high capacity, which will ensure longer operating time of the screwdriver;
• smaller size and weight;
• Retains charge well when not in use.

But a lithium battery for a screwdriver does not withstand full discharge well, so factory tools on such batteries are equipped with additional circuit boards that protect the battery from overheating, short circuit, and overcharging to avoid explosion or complete discharge. When the microcircuit is installed directly into the battery, the circuit opens if the unused battery is located separately from the tool.

Difficulties in reworking

IN Li-Ion batteries there are objective shortcomings, such as poor performance when low temperatures. In addition, when converting a screwdriver to 18650 lithium batteries, you may encounter a number of difficulties:

1. The 18650 standard means that the diameter of one battery cell is 18 mm with a length of 65 mm. These dimensions do not coincide with the dimensions of the nickel-cadmium or nickel-metal hydride elements previously installed in the screwdriver. Replacing batteries will require placing them in a standard battery case, plus installing a protective microcircuit and connecting wires;
2. The output voltage of lithium cells is 3.6 V, and for nickel-cadmium cells it is 1.2 V. Let’s say the nominal voltage of the old battery is 12 V. This is the voltage when connected in series Li-Ion cells cannot be provided. Voltage fluctuations during charge-discharge cycles ion battery also change. Accordingly, converted batteries may not be compatible with the screwdriver;
3. Ion batteries differ in the specifics of their operation. They do not withstand overcharge voltages greater than 4.2 V and discharge voltages less than 2.7 V until they fail. Therefore, when the battery is rebuilt, a protective board must be installed in the screwdriver;
4. The existing charger may not be able to be used for a screwdriver with a Li-Ion battery. You will also need to remake it or purchase another one.

Important! If a drill or screwdriver is cheap and not of very high quality, then it is better not to remodel it. This may cost more than the cost of the tool itself.

Battery selection

Screwdrivers often use 12 V batteries. Factors to consider when choosing Li-Ion battery for a screwdriver:

1. Such instruments use elements with high discharge current values;
2. In many cases, the capacity of the element is inversely related to the discharge current, so you cannot select it based on capacity alone. The main indicator is current. The value of the operating current of the screwdriver can be found in the tool passport. Usually it is from 15 to 30-40 A;
3. When replacing a screwdriver battery with a Li-Ion 18650, it is not recommended to use cells with different capacity values;
4. Sometimes there are tips to use a lithium battery from an old laptop. This is absolutely unacceptable. They are designed for a much lower discharge current and have unsuitable technical characteristics;
5. The number of elements is calculated based on the approximate ratio - 1 Li-Ion to 3 Ni-Cd. For a 12-volt battery, you will need to replace 10 old cans with 3 new ones. The voltage level will be slightly reduced, but if you install 4 elements, then increased voltage will shorten the life of the electric motor.

Important! Before assembly, it is necessary to fully charge all elements for equalization.

Disassembling the battery case

The case is often assembled using self-tapping screws, other options are assembled using latches or glue. The glued block is the most difficult to disassemble; you have to use a special hammer with a plastic head so as not to damage parts of the body. Everything from inside is removed. You can reuse only the contact plates or the entire terminal assembly for connecting to a tool or charger.

Battery Cell Connection

CompoundLi– Ionbatteries for screwdriverperformed in several ways:

1. The use of special cassettes. The method is fast, but the contacts have a high transition resistance and can quickly be destroyed by relatively high currents;
2. Soldering. A method suitable for those who know how to solder, since you need to have certain skills. Soldering must be done quickly, because the solder cools quickly, and prolonged heating can damage the battery;
3. Spot welding. Is the preferred method. Not everyone has welding machine, such services can be provided by specialists.

Important! The elements must be connected in series, then the battery voltage is added, but the capacity does not change.

At the second stage, the wires are soldered to the contacts of the assembled battery and to the protective board according to the connection diagram. Wires with a cross-sectional area of ​​1.5 mm² are soldered to the contacts of the battery itself for power circuits. For other circuits, you can take thinner wires - 0.75 mm²;

A piece of heat shrink tubing is then placed over the battery, but this is not necessary. You can also put heat shrink on the protective microcircuit to isolate it from contact with the batteries, otherwise sharp solder protrusions can damage the shell of the element and cause a short circuit.

Further battery replacement consists of the following steps:

1. The disassembled parts of the body are well cleaned;
2. Since the dimensions of the new battery cells will be smaller, they need to be securely fixed: glued to the inner wall of the case with Moment glue or sealant;
3. The positive and negative wires are soldered to the old terminal block, it is placed in its original place in the case and fixed. The protective board is laid, the parts of the battery pack are connected. If they were previously glued, then “Moment” is used again.

The lithium-ion battery of the screwdriver will not be able to function properly without the BMS protection board. The copies sold have different parameters. The BMS 3S marking assumes, for example, that the board is designed for 3 elements.

What you need to pay attention to in order to choose a suitable microcircuit:

1. The presence of balancing to ensure uniform charge of the elements. If it is present, the description of the technical data should include the value of the balancing current;
2. The maximum value of operating current that can be withstood for a long time. On average, you need to focus on 20-30 A. But this depends on the power of the screwdriver. Low-power ones need 20 A, high-power ones – from 30 A;
3. Voltage at which the batteries are switched off when overcharging (about 4.3 V);
4. The voltage at which the screwdriver turns off. This value must be selected based on technical parameters battery cell ( minimum voltage- about 2.6 V);
5. Overload protection current;
6. Resistance of transistor elements (select the minimum value).

Important! The magnitude of the operating current during overload does not have of great importance. This value is adjusted to the operating load current. In case of short-term overloads, even if the tool has turned off, you must release the start button, and then you can continue to work.

Whether the controller has an autostart function can be determined by the presence of the “Automatic recovery” entry in the technical data. If there is no such function, then in order to start the screwdriver again after the protection has tripped, you will need to remove the battery and connect it to the charger.

Charger

The lithium-ion battery of the screwdriver cannot be charged by connecting it to a conventional power supply. A charger is used for this. The power supply simply produces a stable charge voltage within specified limits. And in the charger, the determining parameter is the charge current, which affects the voltage level. Its meaning is limited. The charger circuit contains nodes responsible for stopping the charging process and other protective functions, for example, shutdown in case of incorrect polarity.

The simplest memory is a power supply with a resistance included in the circuit to reduce charging current. Sometimes they also connect a timer that fires after a set time period has passed. All of these options are not conducive to long battery life.

Charging methodsLI Ionbatteries for screwdriver:

1. Using a factory charger. Often it is also suitable for charging a new battery;
2. Redesign of the charger circuit, with installation additional elements scheme;
3. Purchase of a ready-made memory. A good option– IMax.

Let's say there is an old Makita DC9710 charger for charging Ni-Cd batteries at 12 V, with an indication in the form of a green LED signaling the end of the process. The presence of a BMS board will allow you to stop the charge when the specified voltage limits per element are reached. The green LED will not light up, but the red one will simply go out. The charge is complete.

The Makita DC1414 T charger is designed to charge a wide range of batteries 7.2-14.4 V. In it, when the protective shutdown is triggered at the end of the charge, the indication will not work correctly. The red and green lights flash, which also signals the end of the charge.

The cost of replacing screwdriver batteries with lithium-ion ones depends on the power of the tool, the need to buy a charger, etc. But if the drill/driver is in good functional condition and the charger does not require major alteration or replacement, then for a couple of thousand rubles you can get an improved power tool with increased battery life.

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