Converting a 12v electric screwdriver to a lithium battery

Learn how to convert an electric screwdriver to lithium-ion batteries with your own hands

the electric screwdriver is so tightly squeezed into the life of modern man that no repair or construction work at home and at work can do without it. The main advantage of the tool is its mobility, which is ensured by a removable self-contained battery. This is why the device in question is called a “cordless electric screwdriver”. Often in operation the question arises about how to convert the battery of an electric screwdriver, because the nickel-cadmium batteries have a big disadvantage in comparison with lithium batteries. it’s low life. To avoid buying a new power tool with a lithium battery, you can upgrade your old battery by replacing the nickel-cadmium banks in it.

The portability of an electric screwdriver is ensured by the use of an independent power source. As such source is a rechargeable battery, the principle of operation of which is similar to the usual battery for a clock or remote control. Only the battery for power tools has a voltage several tens of times greater than that of an ordinary finger-tip battery.

The battery powers the electric screwdriver motor. As the electric motor armature rotates, torque is transmitted to the gearbox. The reducer reduces or increases the rotation speed (depending on the set mode) of the working organ. the chuck in which the bits are fixed. Independent power source as a battery on an electric screwdriver is a key element, without which the operation of the device is simply impossible.

Often owners of inexpensive screwdrivers are faced with such a situation as a rapid discharge of the battery. The reason for this is the material of manufacture of the independent power source. There are three main types of batteries for electric screwdriver:

  • Nickel-cadmium. the simplest, inexpensive and short-lived. Another disadvantage of this material is a small reserve of charge
  • Nickel-metal hydride, an improved version of the cadmium ones, which have an increased resistance to frequent charges and discharges (but they discharge quickly). Exposure to low temperatures has a negative effect on battery life
  • Lithium-ion batteries. this is a new era of batteries, which not only hold a long charge (slow consumption due to high capacity), but can also serve for at least 10 years

Often owners only realize after buying an electric screwdriver that comes with a nickel-cadmium battery that they “should have chosen a power tool with a lithium battery”. The reason for buying a power tool with a nickel-cadmium source is also easy to explain, because with such a battery the device is several times cheaper. If you don’t believe me, you can compare the price of screwdrivers at Cylinder’s online store.

Nickel-cadmium and metal hydride. why you need to replace them

One of the very first batteries to be used in power tools were nickel-hybrid sources. The advantages of these devices include an optimal capacity reserve and a low heat build-up of the cans when compared to hydride ones. In addition, such sources are inexpensive, yet effectively perform their primary function when used properly.

The advantages of nickel cadmium devices include:

  • Low risk of overheating compared with hydride sources
  • Nickel-cadmium sources are contained inside a metal case that provides high stability and sealing performance
  • If properly used, the nickel hydride will last at least 3-5 years, but precisely because the device has to be used frequently in extreme conditions, the life of the battery decreases sharply from the first day of purchase
  • Low cost, which makes these devices popular
  • Not afraid of deep discharge

To extend the service life of the battery, so you don’t have to ask yourself how to convert your electric screwdriver battery to lithium, you need to follow the simple instructions for using Ni-Cd batteries:

  • It is possible and necessary to work with the tool until the battery is completely discharged
  • Charge the source until its capacity is completely replenished
  • Unlike lithium batteries, it is better to store cadmium batteries in a discharged state
  • The “memory effect” is a drawback, but it can easily be eliminated by repeating three charge-discharge cycles

Hydride power supplies appeared after the cadmium ones, but they did not become very popular, because they quickly lose their charge, and they are not suitable for high-power models of screwdrivers. Hydride batteries have no “memory effect” and are less harmful to the environment than cadmium batteries. If your battery, which consists of cadmium or hydride sources, sooner or later you will need to replace it. Buy a new battery for an electric screwdriver of little-known brand or outdated model is almost impossible, so it becomes necessary to modernize the old one. From the old cadmium battery can be made even better, but this will need to figure out how to remake the battery electric screwdriver.

Budget electric screwdriver conversion to Li-ion battery with balancing for 100.

I have an old electric screwdriver, lay idle for a long time, respectively, the batteries have told a long life. And then recently I needed it, the kitchen to assemble. If you’re wondering how I got it back to life with a lithium conversion for less than 100, you’re welcome to come under the hood. My drill is such. 18 volt, 9Nm at a glance I had three options 1. Buy a new inexpensive electric screwdriver for 1500-2500r. easy, fast, but this is not our way, because the old drill will be dead weight, and throw the hand will not do, 2. order NiCd batteries. about 900-1200r. and the point, if you can get a new one for 1500r? 3. to convert to lithium, but here the budget can be different. After reading the question on the maschka found out that to convert to lithium you ideally need:. board 3S, 4S or 5S depending on the size of the battery (I need 5 banks of batteries for 18 volt drill, respectively 5S. about 800r). preferably the balance board (if the protection board without balancer), especially desirable if the batteries are not new or from different lots. Li-ion batteries themselves, preferably current, those are designed for high current operation. from 350r per piece, for 5 pcs. from 1700r. In the end is a bit expensive for my cheap old drill (see 1 point), so it was decided to do my ultra-budget version with blackjack balancing. I had an old laptop battery (gave it away for nothing), disassembled it and found these Samsung banks. With the exception of 2 cans the rest were quite working, charged each bank checked them after charging the current short circuit (no more than 1 second. it can be dangerous, since banks are without protection). As you can see, the banks are quite alive. short-term short-circuit current of 10 to 20A. Outlined the scheme of modification, it and will do. Since batteries are not current to facilitate their work was decided to put two batteries in parallel (at operating current of 10A for example, the current produced by each ac will be 10/2 = 5A). It is desirable to pick up pairs with similar characteristics of current output. Fixing the circuit: Basically, my drill, judging by the characteristics of not particularly powerful, so in principle it would be possible and one bank to put, though they are likely to live less, but as the battery I had in the amount of 10 pieces decided to put all 10. Assembling process is not photographed, in principle there is nothing interesting, the batteries can be soldered to the already welded blades without fear of overheating. Since all 10 batteries in the old unit did not fit, turned out a little kolhozno well, take the blue (what was) duct tape and hide all the extra. already better) As you see on the side I brought out the charging and balancing connector, which I soldered out of the broken graphics card (or motherboard, I do not remember). Since I need 10 contacts, I had to use a db15, if the battery less applied here would db9. they are easier to find Remains soldered charger. I took five unnecessary cell phone chargers as 5 volt power supplies. I found five of them, but they are all different, with different current from 600 to 900mA. Ideally use the same ones, so the charging would happen about the same time and you could estimate which banks are longer charged. Important! To do exactly according to the scheme using for each controller has its own separate power supply 5-8V, that is, power supplies should be galvanically isolated from each other. One powerful power supply for all controllers can not be used. will be a short circuit the battery (TP4056 common on the input and output case. minus). To reduce the size I took the chargers out of their cases. On the back side glued on the double-sided adhesive tape TP4056 charge controller and put the construction in a separate case This is what it looks like when you turn in a 220V blue charge controller. indicating that the load is not connected (or the ac is charged), red and green. cell phone charger LEDs. Now connect the battery, you can see that only 3 cans are charged (red diode is lit) and the other 2 are not (blue diode is lit). That’s because I charged it recently, and only 3 of the 5 acb’s discharged. So, you can see that each charge is balancing the entire battery. this is a major plus of this scheme, especially important when using these old batteries from a laptop battery. For clarity, took a video, maybe something is missing in the story, then look at the video

To summarize. Pros 1. Cheap. I only needed to buy TP4056 charge controllers, which cost me 60 for 5 pieces, the rest were or got for free. Now shipping from this seller is only paid, about 1 more, you can find cheaper probably. 2. Balancing the batteries on each charge.

Cons 1. No current protection, so I do not put the chuck lock on the lock (drill icon) so the current protection is purely mechanical. the chuck is clicked and not blocked when clamped, no short-circuit current. In principle I think this protection is enough. 2. If you do not have old chargers from cell phones, it will be a little more expensive. But you can ask around, many of your friends probably have them lying around. 3. No overdischarge protection. You need to see if the power dropped, immediately recharge! It’s lithium, you don’t have to wait for the battery to run out like you do with nickel.

In general, I think this scheme has the right to life, especially for the reanimation of such inexpensive and not superpowerful screwdrivers. ps in the Комментарии и мнения владельцев gave a link 60r with shipping

Components needed for conversion

Beforehand it is necessary to pick up components which will help to transform an electric screwdriver. The composition is determined by the peculiarities of the process, namely by soldering, using special cassettes or spot welding. Cassettes are not recommended due to their vulnerability to current. The rest of the list includes:

  • Li-ion18650 batteries
  • A circuit board or module that ensures an even load when charging;
  • contact welding machine. It is preferable to soldering because lithium batteries are sensitive to heat and can fail;
  • Wires with a cross section of 0.75 mm², 1.5 mm², 2.5 mm²;
  • shrink;
  • screwdriver
  • circular knife.

The battery must match the capacity of the old components in the proportion of 1/3. Т.е. Lithium cell is a full replacement for 3 nickel cadmium batteries. Usually use 3 pcs. Li-ion instead of 10 Ni-Mh, which will slightly reduce the power of the unit. It is possible to install 4 batteries, but this will reduce the operating life of the electric motor.

The current value listed on the data sheet of the electric screwdriver is the key. It ranges from 15-40 A, respectively selected elements with similar kickback parameters. This applies to both the batteries and the protection boards. A 25 amp or 30 amp BMS module is a universal option. It is undesirable to use batteries from an old laptop, because they are not designed for high load.

How to remake

The direct replacement of the batteries in an electric screwdriver does not depend on the capacity of the power cells. The process is performed in several steps, starting with the case disassembly of the battery.

Dismantling power supply for new charging

Better if it has a screwed or riveted assembly. Worse if there is an adhesive bonding, in which case everything is done with the utmost care.

Then all elements except the contact plates or terminals are removed from the inside. New batteries are connected to each other in series by the method of your choice (soldering, spot welding). Consistency is the key to success, ensuring consistency of capacity and voltage. For the connection, wires with a cross section of 2.5 mm², capable of withstanding the high voltage during operation, are suitable.

Soldering of wires to stabilization module

Battery module and BMS protection board are connected with wires. Preferably use 1.5 or even 2.5 mm² cross-section. Direct connection scheme consists of:

  • Connect the wire going to the plus side to the corresponding pin of the board, marked B;
  • Connecting the wire going to the minus to the corresponding pin of the board, marked B-;
  • Wires from other contacts of the unit are connected to the terminals marked on the board as B1, B2, B3. Number of connections depends on the number of batteries.

To avoid short circuits, the protective module is insulated from the batteries with a heat shrink, this will keep it from soldering or welding contacts.

Wires soldering of power supply unit with module

On the BMS board itself there are 2 more contacts marked P and P-. From them the wires go to the corresponding terminals of the old chip.

Voltage setting

Set the output voltage on the resistors. Each element must not exceed 4.2 volts.

Placement in enclosure

The final step is to assemble the battery. Enclosure parts are thoroughly cleaned and the battery pack is inserted into the cavities. Given its smaller size, it is attached to the surface by means of glue or sealant.

Wires plus and minus are soldered to the terminals, the terminal block is also placed in the case, followed by a neatly placed protective plate BMS. At the end, the parts of the housing are connected with screws, staples or glue.

The difference between the battery charger and the power pack is the presence of charging current. It determines the voltage level and corresponding limitations. The controller reacts to overload, incorrect polarity, mismatching the output value. As a rule, the device is simply disconnected.

The transformation consists of the addition of the CU, which includes such element as a BMS module, with the adjustment of the resistors. It remains to set the necessary values, upon reaching which the charge stops. Often, when redoing the charger, the green light does not turn on. Instead, the red light just goes out.

Most modern screwdrivers are equipped with a universal battery charger. They work for both nickel-cadmium and lithium. You can buy a ready to use charger, but it is an additional investment.

Summarizing, to remake the battery of an electric screwdriver to Li-ion 12 volt or 14, 18 volt, you need a set of components, experience in working with electrical equipment and a little free time. It is advisable to calculate the total cost of the investment in advance. Repair. a long procedure, so sometimes it is easier to buy a new electric screwdriver, their price today is not high.

The process of remaking

The first thing to do is to disassemble the battery and take out the old banks. From them, you will also need to separate the plates with which they are soldered, because they will solder the new batteries.

It is also necessary to remove the terminal part.

Next, you need to disconnect these terminals and prepare two thick power wires.

It is necessary to buy a special board and three high-current batteries format 18650. (references to all components will be in the description of the video). In terms of cost comes out within 1k. It is better not to save money on batteries and buy good ones.

I think everything is clear from the photo below. Just solder everything as pictured and it will work just fine. Already on such a principle has remade more than one electric screwdriver and all works fine.

I also soldered two power wires and a socket for recharging. The socket is taken from the modem circuit board. The battery charger comes from my second 12v electric screwdriver, which is already powered by lithium batteries, but if you do not, then there are chargers where you order the board. You can’t charge it with the regular charger after the conversion. Preliminary check everything before packing in the case.

It is now necessary to remove all the innards from the battery case.

As you can see all the batteries and board fit just fine in the housing.

I made the charging jack on top of the battery. It is easy to charge it without removing it.

The terminal part and the charging jack fixed with hot melt glue. It’s holding up well.

After reassembly, everything works perfectly. Everything you need from an electric screwdriver works great. clearly you can see in the video below.

The board does a good job with charging. As you can see from the photo below, the red indicator light is on when charging.

After the batteries are charged, the indicator light turns green.

So, in this simple way we gave the screwdriver a second life! I hope my article was helpful!

What are the complications of remodeling?

Before we start, we need to determine the feasibility of modification. It’s better not to overhaul a tool that has been in use for a long time, because it’s not profitable.

The price of necessary materials and efforts will be 2/3 of the cost of the equipment.It is more reasonable to buy a new electric screwdriver or drill. It is worth thinking about other things:

  • Lithium rechargeable batteries of the 18650 standard (only they will fit as a replacement) are 6.5 cm and a diameter of 1.8 cm. Ni-CD socket is not suitable for Li-ion. Batteries must be placed in the battery case. You will need to wire and wire the protective circuitry yourself.
  • Li-ion output voltage is 3.6 В. This parameter of Ni-CD is equal to 1.2 В. New batteries may not be compatible with your equipment.
  • Lithium-ion battery packs will not withstand a recharge voltage greater than 4.2V and a discharge of up to 2.7 В. Operating in this mode will very quickly destroy the battery cells, so installing a protective plate is mandatory.
  • The original battery charger (provided with your Ni-CD equipment) cannot be used with Li-ion in 8 out of 10 cases. A new one will have to be purchased. If not in the plan to buy, then it is also necessary to convert the charger of the electric screwdriver to work on lithium batteries, which can also have its own difficulties.

Reworking your tool is not the way to avoid all the inconveniences.

The new lithium battery exhibits poor performance at low temperatures. It is necessary to weigh all the pros and cons, starting to work.

Pros and cons of electric screwdriver upgrade

One disadvantage is already mentioned. the rapid decrease of battery capacity at ambient temperatures below 7-100C. There is another. the price of batteries, but unlike Ni-CD cells, lithium-ion batteries are much more durable. Nickel-cadmium batteries are chemically unpredictable. If one battery fails, the remaining ones will not provide the voltage needed to operate the equipment.

  • Lithium-ion batteries have twice the capacity of nickel-cadmium batteries with the same parameters;
  • No “memory effect” on the charge. Charging can be done with any cell discharge, at any time.
  • The 18650 standard will lighten the weight of the design. It will be easier and easier to work.

Do not forget about the need to install a protective circuit board (overheating, the Li-ion cell explodes, can provoke a fire) in the course of the work.

Converting electric screwdriver to Li-ion without BMS

Many craftsmen have a cordless electric screwdriver on duty. Over time, the battery degrades and holds less and less charge. Battery wear and tear has a big impact on battery life. Constant recharging doesn’t help. In this situation, “repacking” the battery with the same cells helps. The most commonly used cells in electric screwdriver batteries are the “SC” size. But the most valuable thing in the master is the repair with your own hands.Rebuilding an electric screwdriver with a 14 battery.4 volt. Screwdrivers often use a motor for a wide range of supply voltage. So, in this case you can use only three Li-ion 18650 cells. I will not use control boards. The discharge of the cells can be seen at work. As soon as you do not tighten the screw, for example, it is time to put on the charge.

Converting an electric screwdriver to Li-ion without BMS board

Let’s start by taking our battery apart. There are 12 cells inside. 10 pieces in one row and 2 in the second row. The contact group is welded to the second row of elements. We leave a couple of elements with a contact group, the rest we recycle.

Now we need to solder the wires for further work. The contacts are from a material that can not be tinned, so we solder the wires to the cells. Minus to the cell body and plus directly to the plus stud. The old cells serve as a support and do not participate in the work.

I will use a 18650 lithium-ion battery pack. The parts are buu. I need the high current elements for the rework. I “changed” my cells into the Sanyo shrink-wrap, the old one was pretty worn out. Checked the residual capacity Imax.Connect the batteries in series and solder the headers. The battery is almost done.

Now provide a comfortable charging. You need to install a four-pin connector. I used the connector from my old motherboard for the number of pins I needed. I took the mating part from an old computer power supply.

Cut the hole for the connector. Fill the connector with epoxy glue or super glue and baking soda. Also solder the wires.

Solder the wires to the cells. The wire from the first contact of the connector to the plus of the battery. The wire from the second pin of the plug to the plus of the second cell, the same minus of the first cell, and so on. Since I will be charging with a “smart” charger, you need to make a balancing wire.

For the connection to the charger, I will use the cable from the computer power supply unit. The wire which was used to power the floppy disk drive. Cut off all the keys from the connector and it fits perfectly under the charger. It’s simple to unsolder. Red wire to the first pin of the battery connector. The black wire to the second pin of the battery connector and t. д.

We connect it to the charger and don’t forget about the power wires. The wire is the balancing wire. Set the balance on the charger and wait for a full charge.

How to remake and assemble?

Often the craftsman already has an old cordless electric screwdriver, which he is completely satisfied with. But the device is equipped with outdated nickel-cadmium batteries. Since the battery needs to be replaced anyway, you may want to replace the old battery with something newer. This will not only provide a more comfortable operation, but also eliminate the need to search the market for batteries of an outdated model.

The easiest thing that comes to mind is to assemble a power supply from an electronic transformer in the case of an old battery. Now you can use the electric screwdriver by connecting it to a household power grid.

Models with a voltage of 14.4 volt can be connected to car batteries. If you assemble the adapter-extender with terminals or the cigarette lighter plug from the body of an old battery, you get an indispensable device for garage or work “in the field.

If we are converting an old battery into lithium, you can take into account the fact that on the market are extremely widespread lithium cells standard 18650. So we can make batteries for electric screwdrivers using readily available parts

over, the prevalence of the standard 18650 allows you to choose batteries from any manufacturer.

It is not difficult to open the casing of an old battery and remove the old stuffing

It is important not to forget to mark the contact on the housing, which previously was connected to the “plus” of the old battery pack

Depending on the voltage for which the old battery was designed, it is necessary to select the number of lithium cells connected in series. The standard voltage of a lithium cell is exactly three times that of a nickel cell (3.6 volts instead of 1 volt.2 В). So, each “lithium” cell replaces three “nickel” cells connected in series.

By providing a battery design in which three lithium cells are connected one after the other, you can get a battery with a voltage of 10.8 volts. These are common, but not very common, among nickel batteries. If you daisy-chain four lithium cells, you get 14.4 volts. This will replace a 12 volt nickel battery as well as a 14 volt.4 volts is a very common standard of nickel cadmium and nickel metal hydride batteries. It depends on the specific model of electric screwdriver.

After you have managed to determine the number of consecutive steps, you will probably find that there is still room in the old case. This will connect two cells in each stage in parallel, doubling the capacity of the battery. Production plants use nickel strip to connect lithium batteries to each other. Tape strips are joined together and to the lithium cells by means of contact welding. But in everyday life, soldering is quite acceptable.

Solder lithium cells with extreme care. Clean the joint thoroughly beforehand and apply good flux. Soldering is done very quickly, with a properly heated soldering iron of sufficiently high power.

Soldering itself is done by quickly and surely heating the connection point between the wire and the lithium element. Soldering time should not exceed three to five seconds in order to avoid the dangerous overheating of the cell.

The good thing is that electronic control and balancing modules are now available at fairly low prices. It is sufficient to choose the solution that suits the specific case. In general, such controllers differ in the number of “stages” connected in series, the voltage between which is to be equalized (balanced). They also differ in terms of the permitted load current and the way in which the temperature is monitored.

In any case, you can no longer charge a homemade lithium battery with your old battery charger for nickel batteries. They have fundamentally different charging algorithms and reference voltages. A specialized charger is needed.

Which Lithium Battery to Choose?

Screwdrivers use 12 volt batteries in 7 out of 10 cases.

Voltage is the deciding factor in your choice. This can be found on the internet or in the technical documentation of the machine.

  • the value of the discharge current. Screwdrivers are powered by batteries with a high discharge current parameter. To clarify the required parameter for a particular model can be found in the technical documentation. It is a mistake to choose the battery only by its capacity, because the main parameter is the current. It can range from 15-30A, sometimes up to 40A.
  • The characteristics of the lithium-ion cells. Batteries of the 18650 standard must have the same capacity characteristics.
  • Number of new batteries. The calculation is easy. The ratio is as follows. 3 Ni-CDs equal 1 Li-ion. Replace the old 12-volt block with a block of 3 lithium-ion cells.

When calculating the number of new sources remember that the increased voltage (for example, instead of 3 Li-ion instead of 10 Ni-CD take 4 lithium batteries) will increase wear and tear of the equipment, reduce life. But the power will increase. So you need to weigh all the pros and cons. Do not rush with the installation of the sources in the tool. They must first be fully charged.

Converting an electric screwdriver to lithium batteries

Over time, the native nickel-cadmium batteries of an electric screwdriver lose their capacity, the charge is enough for a couple of screws, and the charge takes a couple of minutes. If you are faced with such a problem, the first thing that comes to mind is to buy a new battery or electric screwdriver. But you can give a screwdriver a second life and convert it to lithium battery (of course, if the electric screwdriver is not killed and appropriate). As an example, I will use an electric screwdriver “Soyuzmash ASh-14M” with a voltage of 12 V.

Needed parts: Electric screwdriver Soyuzmash ASh-14M x 1 pc; Battery LiitoKala HG2, 18650, 3000 mAh x 3 pcs; BMS 3S, 40A, 12.6V with balancing x 1 pc; XL4015 step-down converter x 1 pc; 1.5 mm wire (black, red). 20 cm.

disassembly of the case:In my case, the battery case is fastened with screws, also there is a variant with latches or glue. The most difficult thing to disassemble the laminated block, for disassembly use a special hammer with a plastic base. Everything is removed from inside the battery pack, we only need the contact plates, to connect to the screwdriver and charging station.

Battery choice:Electric screwdriver ASh-14M is designed to work from a 14 V battery, so I will use three lithium-ion batteries with a total voltage of 12.6 V, of course you can use four batteries and raise the voltage to 16.8, but then you must use a separate power supply, as well as high voltage reduce the life of an electric screwdriver. Not all batteries will be suitable for the conversion of the battery, so you need to consider several factors:

It is not recommended to use rechargeable batteries with different capacities; You can not choose batteries only by capacity, the main parameter is the discharge current. Some people recommend using lithium batteries from old laptops, this is not correct, they are designed to work with a lower discharge current.

In this article, I use LiitoKala HG2 batteries, size 18650, 3000 mAh capacity and a current discharge of 30A, are available with and without soldered “tails”, in my case without, for convenience, I advise to buy batteries with “tails”

Selection of BMS board: A lithium-ion battery pack cannot be used without a BMS board. There are different numbers on the market with different parameters. The marking BMS 3S, indicates that the board is designed for three batteries. The marking BMS 3S implies for example that the board is designed for 3 cells. What you need to pay attention to:

The presence of a balancer ensures that the batteries are charged evenly. Maximum long-term operating current.

In this article I use BMS 3S, 40A, 12.6V with balancing, it is well proven.

Battery modification (assembling): I use batteries without soldered tails. I will solder the leads directly to the terminals and I use 60W soldering iron or bigger power to avoid overheating the battery.

Warning! Never overheat the battery.

We take acid, solder and tin both sides of the battery terminals and solder wires, as well as instead of wires you can use nickel-lithium tape, which can be bought or take from an old battery. In my case I use a wire with the thickness of 1 square meter because the place does not allow to put the battery evenly and the tape will not reach. After soldering all the wires, we take all the batteries and bind them with duct tape. There are now a variety of battery holders available.

Now according to the schematic, in series solder each battery output from 0 to 12.6, so first solder to 0, then 4,2, then 8,4, then 12,6 to the BMS 3S board

Then we solder the wires with cross section not less than 1,5 squares to the contact pads and fix them in the battery case with hot melt. Some people leave two old batteries, so that the contact group does not fly out.

We solder the wires from the contact plates to the BMS board, observing the polarity and assemble the battery case in the reverse order and everything is ready.

Adaptation charger: Included with an electric screwdriver Soyuzmash ASh-14M, is the charger, but it is designed for charging nickel-cadmium batteries to charge the lithium-ion battery needs to finalize it. Of course, some people use chargers without modification, but it’s not right.

Revision is to add a board to reduce the voltage and limit current, proved to be a good board on the chip XL4015.

I don’t see the point in describing the fine tuning, because for each charger is different, but the essence is that you need to cut a couple of tracks on the charger board and from the output circuit transformer soldered to the input with XL4015. Next, you need to set the voltage to 12.6 V, in my case 3S or 16.8 V for 4S, and set the current to 1A, if you put more current, charging will go faster, but the batteries will fail quickly, if less, charging will be longer.

And how many batteries to buy?

A charged 18650 battery gives 4.2 volts. Divide the voltage from which the electric screwdriver works by 4.2 and round up (for 12 volt electric screwdriver. 3 batteries).

After that carefully open the battery compartment. There will be a battery assembled from nickel-cadmium batteries.

The upper batteries are spot-welded to the contact group of the battery compartment of the electric screwdriver. Disconnect the batteries from the terminals with a knife, if this does not work, bite the contact patch going from the terminal to the battery, above the welding point. After removing the battery, dispose of it at the point designated for this purpose.


The project implies a quick removal of the batteries (so that at the end of work, you can easily put them on a stationary charger, such as NITECORE I4 (At https://sdelaysam-svoimirukami.There are also articles on how to build a budget charger for these batteries)), so were used holders 2 x 18650.

To achieve the desired voltage, the batteries must be connected in series (In this connection, the plus side of the battery is connected to the minus side of the subsequent battery). Since I used 2 holders, they need to be connected to each other for current exchange

The original leads of the holders were too thin, which could have caused heating losses. To avoid this the leads were soldered to larger diameter leads to suit the new battery layout.

For a rough indication of the battery charge level a 12v LED connected in series with a current limiting resistor of 1kOhm was used.

The power supply of the LED should be brought out in parallel with the power supply of the electric screwdriver. For this purpose a wire with smaller cross section was soldered to the thicker plus and minus wires of the battery block.

The wires with a larger cross section should be soldered to the battery terminals of the electric screwdriver, in my case they are placed on a separate plate, and then the plate should be returned to its original position, fixing it with glue if desired.

To observe the LED in the body of the battery compartment it is necessary to make a hole (a heated nail will do well for this).

Since the LED is an indicator and not a light, you can fix it in the hole by applying thermal glue (this will make the glow softer). Photo of an electric screwdriver after recycling.

Note that in order for the batteries to work properly in series, they must be “married”, in other words, they must come from the same batch, the same capacity and model. If this rule is followed, they will be discharged at the same time. To check the batteries and prevent overdischarge, use an LED (the lower the charge, the dimmer the light it emits. It is not easy to do without proper training, so be sure to check the voltage of the batteries with a voltmeter).