Alteration of a battery of an electric screwdriver to li-ion 12v

Putting together a lithium-ion battery

Here are the new elements of Sanyo UR18650NSX (according to this article they can be found on Aliexpress) with a capacity of 2600 mAh. For comparison, the old battery had a capacity of only 1300 mAh, half the size.

alteration, battery, electric, screwdriver, li-ion

It is necessary to solder the wires to the elements. The wires must be taken with a cross section of at least 0.75 sq. Mm, because we will have considerable currents. A wire with such a cross section normally works with currents of more than 20 A at a voltage of 12 V. You can solder lithium-ion cans, 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 you’re done.

We solder the other ends of the wires to the board according to the diagram.

I always put even thicker wires of 1.5 sq. Mm on the battery contacts. because the space allows. Before soldering them to the mating contacts, I put a piece of heat-shrinkable tube on the board. It is necessary for additional isolation of the board from battery cells. Otherwise, the sharp edges of the solder can easily rub or puncture the thin film of the lithium-ion cell and cause a short. It is possible not to use heat shrinkage, but at least something insulating to be laid between the board and the elements is absolutely necessary.

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

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

The battery is charged with a standard charger. True, the algorithm of work is changing.

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

How to disassemble a screwdriver battery

How to disassemble an old battery? There are batteries where the halves of the case are fastened with screws, but there are also glue ones. My batteries are one of the last ones, and I generally believed for a long time that they could not be disassembled. It turned out that it is possible if you have a hammer.

In general, with the help of intense 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 in the hand by weight), the gluing site is successfully separated. In this case, the case is not damaged in any way, I have already disassembled 4 pieces this way.

From the old circuit, only contact plates are needed. They are permanently spot welded to the upper two elements. You can pick out the welding with a screwdriver or pliers, but you need to pick it 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 thermal sensor and disconnector, 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 a standard charger. Therefore, I highly recommend saving them.

Battery conversion of Black & Decker Cordless Screwdriver

Converting the battery of the screwdriver to Li-Ion

I won’t say anything new in this article, but I just want to share my experience of upgrading the batteries of my old Makita screwdriver. Initially, this tool was designed for nickel-cadmium batteries (which have long since died, just as those bought for replacement have died). The disadvantages of Ni-Cd are well known: low capacity, short lifespan, high price. Therefore, cordless tool manufacturers have long since switched to lithium-ion batteries.

Well, what about those who have an old instrument? Yes, everything is very simple: throw away the Ni-Cd cans and replace them with Li-Ion of the popular 18650 format (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 1.3 Ah battery. At the maximum charge level, it has a voltage of 10.8 volts. Lithium-ion cells have a nominal voltage of 3.6 volts, with a maximum voltage of 4.2. Therefore, to replace the old nickel-cadmium cells with lithium-ion cells, I need 3 cells, their operating voltage will be 10.8 volts, the maximum is 12.6 volts. Exceeding the rated voltage will not damage the motor in any way, it will not burn out, and with a larger difference, there is no need to worry.

Bosch Cordless Drill Ni Cd to Li Ion Battery Conversion

Lithium-ion cells, as everyone has known for a long time, categorically do not like overcharging (voltage above 4.2 V) and excessive discharge (below 2.5 V). When the operating range is exceeded, the element degrades very quickly. Therefore, lithium-ion cells always work in tandem with an electronic board (BMS. Battery Management System), which controls the cell and monitors 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 out of the operating range. Therefore, in addition to the elements themselves, such a BMS board is 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 cells themselves and the maximum operating current of the BMS board.

In a screwdriver, operating currents at high load reach 10-20 A. Therefore, you need to buy elements that are capable of delivering high currents. Personally, I have successfully used Sony VTC4 30-amp 18650 cells (2100 mAh capacity) and 20-amp Sanyo UR18650NSX (2600 mAh capacity). They work fine in my electric screwdrivers. But, for example, Chinese TrustFire 2500 mAh and 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 with the maximum permissible discharge current.

Likewise, the BMS board must be rated for high operating currents. I saw on YouTube how people collect batteries on 5 or 10-ampere boards. I don’t know, personally, when I turned on the screwdriver, such boards immediately went into defense. In my opinion, this is a waste of money. I will say that the Makita company itself puts 30-ampere boards in its batteries. Therefore, I use 25 Amp BMS bought from Aliexpress. They cost about 6-7 and are searched for “BMS 25A”. Since you need a board for an assembly of 3 elements, you need to look for such a board, in the name of which there will be “3S”.

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Another important point: some boards have different contacts for charging (designation “C”) and load (designation “P”). For example, the board can have three pins: “P-“, “P” and “C-“, as on the native Makitov lithium-ion board. Such a fee will not work for us. Charging and discharging (charge / discharge) must be done 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 threw out a lot of money both on the wrong elements and on the wrong boards, having made all the mistakes that could be made. But I got invaluable experience.

Makita DC9710 charger and lithium-ion battery

Previously, the battery 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 have installed is engaged in level control and power off. 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. Off. charging completed, battery 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 goes 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 with a maximum total voltage of 12.6 V), the charger will blow the roof. Because he will not understand what kind of battery he is charging: either 9.6-volt, or 14.4-volt. And at this moment Makita DC1414 will enter error mode, alternately blinking red and green LED.

This is normal! Your new battery will still charge. though 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 you can survive.

In total, the battery upgrade cost about 1000 rubles. Makitov’s new Makita PA09 costs twice as much. over, we ended up with twice the capacity, and further repairs (in the event of a slight failure) will consist only in replacing lithium-ion cells.

Note: This article and the images in it are subject to copyright. Partial or complete reproduction on other resources without consent is prohibited.

Alteration of the native charger (eerie collective farm):

We will remake with the calculation of the possibility of charging the old type of batteries.

We take our Chinese board, connect it to the laboratory power supply unit, set it to 19v, or disassemble the charging and cling to the diode outputs.

We turn the voltage trimmer resistor and set the output voltage to 15V. native Ni-Cd batteries have a full charge voltage of 1.4v-1.5v, and we have 10. For a new battery assembly, this parameter is indifferent, the main thing is more than 12.6v.

UPD: The protection board with the balancer automatically disconnects the batteries when the voltage on the batteries is 12.6V, so the 15V voltage is not important to us. It is important to us when charging old batteries. there is no protection board.

We switch the multimeter to the current measurement mode. We unscrew the current trimming resistor counterclockwise (like in this direction) to the end, i.e. we set the minimum output current. We connect the ends of the multimeter to the output, close the circuit, set the current to 1A. The more current, the faster our battery will charge, but everything will also get hotter. Don’t put more than 1.5A out of harm’s way. This completes the board setup.

We disassemble our memory. To implement the new board, we will need to unsolder the native memory board, remove everything except two LEDs, a diode bridge, and a smoothing capacitor, as well as the battery connector itself. This is done because we will not be able to plug in the new board. the body kit interferes with the board. I decided to leave the original board intact and make a collective farm.

Berm a breadboard, diode bridge, capacitor, two LEDs, or we solder it all from the motherboard. We also solder the contact connectors.

Next, we need to collect on the layout, see fig. (as I could) what is circled in black line.

And solder our LEDs as shown. Brown is a minus for us, and orange is a plus (what wires were there). So that we do not break off the wires at the soldering point, we will fill them with hot melt glue. We solder everything according to the scheme. Do not mix up the polarity of the capacitor and all connections. We attach the LEDs in the case with hot melt glue.

As a result, we have such a collective farm.

Now we check everything, collect and use. For me, the protection with this board does not work when pressed, but with a hand, perhaps, make it work. The charge lamp turns off when the charge current is less than 10% of the set, i.e. less than 0.1A


We use batteries with ponytails already welded on. First of all, we remove the protection from the tails, then we need to tin the ends. Tinning without the use of acid (carefully) you will not succeed in such a way that we take acid, a soldering iron and solder and tinker. We trick from both ends. We apply the acid in a thin layer, this is quite enough, otherwise you will get splashes in different directions.

If you bought acid without a brush, you can pour it into a tube of nail polish, or you can use a disposable syringe, where you squeeze out a drop and immediately pull it back, leaving a thin film. We also need to tin the pluses of the first two batteries, in these places we will connect the batteries to each other.

After you have tinned everything, we solder the batteries in series, see fig. On one of the batteries, the tab is turned in the opposite direction. We also make soldering with a powerful soldering iron, simply by attaching the tongue and pressing the tip of the soldering iron. This is what we should get.

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Now we fix everything with electrical tape or it can be done in advance before soldering. Glue double-sided tape to fix the board.

BOSCH Upgrade Battery / Change Old Dead Li Ion Cell / GSR BAT411

We disassemble the native battery. We take out the old batteries (Caution).

We bite off the black piece and solder it. We need thick wires. we will have currents up to 25A in periods or more. that with thin wires can lead to their fire, as well as we will have a loss in power. Carefully put the batteries aside.

Now we need to find a thick, wide, relatively soft pad of 1.5-2cm. I tore it from the packaging of a certain gadget. Cut out the size of the case and put it on the bottom, glue the double-sided tape and glue the batteries. We fix that black thing, the protruding end should be of such length that it rested against our batteries and allowed the case to be closed with a certain interference. Do not mix up polarity!

In this case, the brown wire is minus, and the black wire is plus. Brown is an order of magnitude thicker than black.

We cut the wires, making them as short as possible, so as not to lose current through losses, but we must take into account that we still need to be soldered to the board. We solder and assemble the case, the battery is ready.


You can use 6 pcs. 18650 battery, which will double our battery capacity, but will require a higher charge current, which will require abandoning the original power supply without alterations, and our charging will last oooooooooo long.

I want to draw your attention and this is very important, the batteries in the photo are not suitable for our task, this is my jamb, I bought it without thinking. Use only high amperage batteries. But since I had no options, I did on them.

Why do we need high-current batteries. lithium batteries are designed for use under certain conditions of discharge charge, those in the photo allow them to be rarefied with currents of 2C i.e. in this case, it is about 6 A. The electric screwdriver at the moment of start consumes a current from 15A to 25A and at a constant load of about 10A. As we can see, we have exceeded the manufacturer’s requirements. High-current batteries are designed for higher discharge currents from 10A, which guarantees us a longer service life, as well as fewer surprises in the future from improper use. Read about such batteries: read

Board with protection and balancing. will allow us to operate lithium batteries within the limits recommended by manufacturers. It will protect our batteries from deep discharge, as well as from overcharging, which is very critical for lithium batteries and violation of this point will lead to very rapid degradation of the battery, i.e. loss of its capacity. Also, this board has a balancing circuit, which is designed to equalize the charge on each battery cell. Our batteries have a serial connection, which during operation will lead to their uneven charge read, which will lead to see paragraph 1, but this board will eliminate this effect. The presented board, upgraded at the request of workers and self-healing when the protection is triggered.

You can use a ready-made battery with an existing charger, but:

  • – there are complaints that the case will be very hot, which many fear. But the design of the charger uses a transformer and heating is normal for it. In my experiments at a current of 1A, it warmed up to 60C. The design does not provide for a current limiting system so that the current in the system can be several times higher and the heating is higher. At the same time, now we need more time to charge the batteries.
  • – in the design of the charger there is a system for limiting the charging time and it is one hour. Those. we will have to juggle the battery to fully charge it.
  • – It will be hard to use the native charger if we decided to use 6 18650 cells, since the maximum current given out according to the manufacturer’s statement should be 1.8A. Those. prolonged use at currents above this value may lead to unknown consequences. For 3 cells with a capacity of 3000mAh and a recommended charge current of 0.5C.1C (1.5A. 3A), we fit into the parameters of the charger. For 6 cells, we need a charge current twice as much. And yes, as I said before, there is no charge current limiting circuit in the charger, i.e. in a certain period of time we will charge our batteries at the aisles of the charger’s capabilities, which is tolerable for 3x, but not for 6 cells.

In principle, these are the main nuances of using a native charger.

Charger (no need to remodel):

  • – buck DC-DC voltage converter (XL4015). Read the article about these converters
  • – breadboard, for example. We need a plump board.
  • – 4 diodes from 100V 3A or a ready-made diode bridge, I used to watch. Or it will be taken from the original charging board.
  • – capacitor from 470mkf 35V. Or it will be taken from the original charging board.
  • – two LEDs of different color 5mm.
  • – hot melt
  • – wires of various lengths and cross-sections.
  • – drills 2mm

For the alteration according to my version, we need:

  • – electric screwdriver Interskol Da-12ER-02)))
  • – soldering iron from 60W because less powerful you cannot dissolve
  • – multimeter (tester)
  • – “Soldering acid”. there are many variations of them, we take with a brush


If you do not have something from the list above, then it is better not to start work because crap you yourself will create more than you will do work.


  • lithium batteries 18650, for example, we take batteries with tails. We need high current batteries.
  • balancer protection board 3S 40A 12.6V 40A lithium battery protection board
  • wires are short, but thick with a cross section of 1.5
  • Double-sided tape
  • thick wide relatively soft pad 1.5-2cm

The advantages of lithium-ion batteries

Nickel-cadmium batteries have a low price, withstand many charging cycles, and are not afraid of low temperatures. But the capacity of the battery will decrease if you put it on charge without waiting for a full discharge (memory effect).

Lithium-ion batteries offer the following benefits:

  • high capacity, which will provide a longer operating time for the electric screwdriver;
  • smaller size and weight;
  • keeps charge well when inoperative.

But a lithium battery for an electric screwdriver does not withstand a full discharge, so factory tools on such batteries are equipped with additional boards that protect the battery from overheating, short-circuit, overcharge in order to avoid an explosion, a complete discharge. When the microcircuit is inserted directly into the battery, the circuit is opened if the unused battery is separated from the tool.

Tips for choosing a security chip

The lithium ion battery of the electric screwdriver cannot function normally without the BMS protection board. Instances on sale have different parameters. BMS 3S marking assumes, for example, that the board is designed for 3 elements.

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

  • The presence of balancing to ensure the uniformity of the charge of the cells. If it is present, the value of the balancing current should be in the description of the technical data;
  • The maximum value of the operating current withstood for a long time. On average, you need to focus on 20-30 A. But this depends on the power of the electric screwdriver. Low-power enough 20 A, powerful. from 30 A;
  • Voltage, upon reaching which the batteries are disconnected when overcharging (about 4.3 V);
  • Voltage at which the electric screwdriver turns off. It is necessary to select this value based on the technical parameters of the battery cell (the minimum voltage is about 2.6 V);
  • Overload protection operation current;
  • Resistance of transistor elements (minimum value selected).

Important! The magnitude of the overload tripping current is not very important. This value is offset from the workload 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.

Connection diagram of elements with a protective board

Whether the controller has an autorun function can be determined by the presence of an “Automatic recovery” entry in the technical data. If there is no such function, then in order to restart the electric screwdriver after the protection is triggered, it will be necessary to remove the battery and connect it to the charger.

Battery selection

12 V batteries are often used for screwdrivers. Factors to consider when choosing a Li-Ion battery for an electric screwdriver:

  • In such instruments, elements with high values ​​of the discharge current are used;
  • In many cases, the cell capacity is inversely related to the discharge current, so it cannot be selected based on capacity alone. The main indicator is the current. The value of the operating current of an electric screwdriver can be found in the instrument’s passport. Usually it is from 15 to 30-40 A;
  • It is not recommended to use cells with different capacities when replacing the battery of an electric screwdriver with a Li-Ion 18650;
  • 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 inappropriate technical characteristics;
  • 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 install 3 new ones to replace 10 old cans. The voltage level will be slightly reduced, but if 4 cells are installed, the overvoltage will shorten the life of the motor.

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

Disassembling the battery case

The body is often assembled on self-tapping screws, other options are assembled with 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 the parts of the case. Everything is removed from the inside. You can reapply only the contact plates or the entire terminal assembly for connecting to the tool, charger.

Difficulties in rework

There are objective disadvantages in Li-Ion batteries, such as poor performance at low temperatures. In addition, when converting an electric screwdriver to lithium 18650 batteries, a number of difficulties can be encountered:

  • The 18650 standard means that a single cell has a diameter of 18 mm and a length of 65 mm. These dimensions do not match the dimensions of the nickel-cadmium or nickel-metal hydride cells previously installed in an electric screwdriver. Replacing batteries will require placing them in a standard battery case, plus the installation of a protective microcircuit and connecting wires;
  • The voltage at the output of the lithium cells is 3.6 V, and on the nickel-cadmium cells. 1.2 V. Let’s say the nominal voltage of the old battery is 12 V. This voltage cannot be ensured when Li-Ion cells are connected in series. The range of voltage fluctuations during the charge-discharge cycles of the ion battery also changes. Accordingly, converted batteries may not be compatible with an electric screwdriver;
  • Ionic batteries differ in the specifics of their work. They do not withstand overcharging voltage more than 4.2 V and discharge less than 2.7 V until they fail. Therefore, when a battery is being reworked, a protective board must be installed in an electric screwdriver;
  • An existing charger may not be used for an electric screwdriver with a Li-Ion battery. You will also need to redo it or purchase another.

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

Battery cell connection

The connection of Li-Ion batteries for a screwdriver is performed in several ways:

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

Important! The elements must be connected in series, then the voltage of the batteries is added up, and the capacity does not change.

At the second stage, wires are soldered to the contacts of the assembled battery and to the protective board according to the connection diagram. To the contacts of the battery itself for power circuits, wires with a cross-sectional area of ​​1.5 mm² are soldered. 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 required. You can also put on heat shrinkage on the protective microcircuit to isolate it from contact with the batteries, otherwise sharp soldering projections can damage the cell shell and provoke a short circuit.

Battery assembly

Further battery replacement consists of the following steps:

  • The disassembled parts of the case are well cleaned;
  • Since the dimensions of the new battery cells will be smaller, they must be securely fixed: glued to the inner wall of the case with Moment glue or sealant;
  • The positive and negative wires are soldered to the old terminal block, it is placed in the same 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.