Makita battery charger conversion to lithium

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

Electric screwdriver is so closely squeezed into the life of modern man, that no repair or construction work at home and at work can do without it. The main convenience 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 there is a question of how to convert the battery of an electric screwdriver, because nickel-cadmium batteries have a big disadvantage compared to lithium batteries. it is a low life span. To avoid buying a new power tool with a lithium battery, you can upgrade the old battery by replacing the nickel-cadmium banks in it.

The portability of an electric screwdriver is achieved by using an independent power source. A rechargeable battery serves as such source, and its operating principle is similar to that of a regular watch or remote control battery. Only a power tool battery has several dozen times the voltage of an ordinary thumbtack battery.

The battery powers the electric screwdriver’s motor. As the electric motor armature rotates, torque is transmitted to the gearbox. The reducer reduces or increases the speed of rotation (depending on the set mode) of the working body. the chuck, in which the attachments are fixed. The independent power source in the role of the battery on an electric screwdriver is a key element, without which the work of the device simply would not be possible.

Owners of inexpensive screwdrivers are often faced with the situation of a rapidly discharging battery. The reason for this is the material of manufacture of the independent power source. There are three main types of batteries for an electric screwdriver:

  • Nickel-cadmium. the simplest, inexpensive and short-lived. Another disadvantage of this material is a small charge reserve
  • Nickel-metal hydride. an improved modification of cadmium, which have 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 are 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 after buying an electric screwdriver that comes with a nickel-cadmium battery, realize that “you 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, since a device with such a battery is several times cheaper. If you don’t believe me, you can compare the price of screwdrivers in the online store Cylinder.

makita, battery, charger, lithium

Nickel-cadmium and metal-hydride batteries. why replace them

One of the very first batteries to be used in power tools were nickel-hybrid sources. The advantages of these devices include optimal reserve capacity and low rates of battery heating when compared to hydride batteries. In addition, such sources are inexpensive, and at the same time effectively cope with their main task if they are used properly.

The advantages of nickel cadmium devices include:

  • Low risk of overheating compared to hydride units
  • Nickel-cadmium sources are contained inside a metal housing, which provides high resistance and tightness
  • If properly operated, the nickel hydride will last at least 3-5 years, but precisely because the device often has to be used in extreme conditions, the life of the battery decreases sharply from the first day of purchase
  • Low cost, which makes such devices in demand
  • Not afraid of deep discharge

To extend the service life of the battery, not to ask yourself how to convert the battery of an electric screwdriver to lithium, you need to follow the simple instructions for the use of Ni-Cd batteries:

  • It is possible and necessary to work with a tool until the battery is completely discharged
  • It is necessary to 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 disadvantage, but it can easily be eliminated by repeating three “charge-discharge” cycles

Hydride ones appeared after the cadmium ones, but they were not very popular because they discharge quickly and 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 will need to replace it. Buying a new battery for an electric screwdriver of a little-known brand or outdated model is almost impossible, so it becomes necessary to upgrade the old one. From an old cadmium battery can be made even better, but to do this you need to figure out how to remake the battery electric screwdriver.

The Makita DC1414 is a car battery charger

In the previous article I told you about rebuilding the battery charger from a Dexter electric screwdriver into a battery charger for car batteries.

In today’s article I will talk about the redesign of a Makita DC1414 charger. The Makita battery charger charges batteries up to 14.4V with up to 2.65A. Disassembled the charger, removed the panel where the battery was inserted, it was soldered to the board with a four pin connector. Got to the board started looking for a schematic of the battery charger in Yandex, but found nothing similar. Then, based on my experience started to work on the circuit board.

I found the pinout pinout of the battery connector on the Makita electric screwdriver. Turns out there are 4 pins on the board: 1. charger 2. thermal breaker 3 charger 4. thermal resistor 18k. The pinout starts from the corner of the board. I connect everything as it should be, with 2 pins kidyu jumper to minus, and between 4 pins and minus put a constant resistor of 20k.

Makita board. The trick with the battery on

Plugging the board into a 220V mains supply. The indicator light turned red, indicating that the battery is charging. To the plus and minus I connect the terminals of multimeter, the output is 27 V. I started to look why such a high voltage. After looking at the optocoupler wiring, I realized that the voltage limitation is set by the gate, which works in breakdown mode. In the original circuit is a 24V regulator, replacing it with a pair of 9.1V and 5.1V at the output was established 14.56V, which is quite acceptable for charging car batteries.

That seemed to be the end of the redesign. I have already filmed a video and uploaded it to YouTube, so that the guys could repeat after me.

But the following happened, testing the charger loaded it on a lamp 12V 100W and after 5 minutes, the unit went into protection. At the output voltage of 1V

Started to understand how the protection is set up, a little bit finalized it and drew the following scheme.

I set voltage 0,25V to the inverting input with the help of divider on the resistors, and cut off the track from the processor. When the voltage drop at the shunt 20,2 Ohm reaches this threshold, on the output Oh there is a constant voltage and through the diode voltage goes to the optocoupler. The circuit operates in current limiting mode.

Well, on this circuit is finally remade and the charger works as it should. The batteries charge perfectly

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Reverting an electric screwdriver to lithium with your own hands

Greetings, DIYers! You can find almost anything at a flea market, from antiques to pretty good power tools. So, during one more trip to the local flea market the author of the YouTube channel “AKA KASYAN” purchased this electric screwdriver for only 1000.

I chose this particular electric screwdriver because, firstly, it is almost new, secondly, it is a complete set with two batteries and a charger, and thirdly, who can refuse such an offer for such a ridiculous price?

There was also a fourth reason. The fact that it is not just a two-speed electric screwdriver, in addition to that there is also a mode of drilling with impact. In cheap screwdrivers this is quite rare, and the good ones with this option cost a lot. Naturally, the modest blow mechanism is in no comparison with the pneumatic mechanism of the peorator, but the strike mechanism is there, and it is a nice bonus.

Included with this electric screwdriver were 2 old nickel-cadmium batteries at 14.4 volts.

The tool is based on the 550th motor. The screwdriver is quite bulky and heavy, but these tools also have. Such an electric screwdriver can be used wherever long autonomous work and a lot of torque is needed.

In general, this article will talk about the redesign of the power tool. The point of this modification is to replace the old nickel-cadmium batteries with lithium-ion ones. Besides the capacity of a new battery has to be at least two-times bigger than the old one, which will increase the time of the electric screwdriver autonomous work. We also assemble a new battery charger for lithium batteries. The charger must be powerful enough to easily be able to charge a high-capacity battery in a couple of hours, give or take.

1) 18650 batteries; 2) Protection board; 3) Heat-resistant adhesive tape; 4) Heat-resistant wire; 5) Fixing compound for 18650

The battery consists of 6 lithium-ion batteries of the 18650 standard. Each two banks are connected in parallel to increase the capacity and current output, and 4 sets of 2 banks in series to increase the total voltage. In other words, it’s a 4s2p battery.

Parameters of the battery are as follows: voltage 14.8V, capacity 4000mAh, it is desirable to use high-current banks with a current return of 15 to 30A.

If you plan to use used batteries, it is important to choose batteries with the same internal resistance. The lower the resistance, the better.

The technical documentation of these batteries says that the bank can be discharged with a maximum current of 4.5A and with a short time current of up to 8A. Peak discharge current is 14A, but not more than 4 seconds. Our battery has 2 banks in parallel, which means that the maximum discharge current can be up to 9A, short-term up to 16A, peak up to 28A respectively. To install the batteries, the holders were printed on a 3d printer.

Of course you can buy the same ones on Aliexpress for pennies, and besides the quality will be much better.

Protection card. Without this thing, you can’t put lithium batteries into service. This circuit board protects the battery against deep discharge, overcharge and short circuits. In this case we used an inexpensive protection card for a 4-cell lithium-ion battery. Board protection current is 15A.

Batteries should preferably be connected by means of nickel tape and a contact welding machine, but you can use, for example, several layers of tinned copper tape, these are used to connect solar modules. When soldering, the main thing is not to overheat the batteries.

Soldering must be fast enough. The soldering process of one solder pad should not exceed 2-3 seconds.

To connect the protection circuit board, you must use wire in heat resistant silicone insulation.

Fix the protection board to the battery through the insulator and fix it with sealant.

Making a home-made battery charger for a converted Li-Ion electric screwdriver.

Adjustable output voltage and charging current. It’s pretty warm but it works.

Adjust the output voltage to 16.8 В. Current to taste 2-3A. For those who want to save batteries at 1-2A. Connect a sufficiently powerful power supply to the input. If the power supply will not give enough current to your settings on the board, then it will not give the current set.

I put everything in the case. Cracked open the old battery charger and glued the top to the new case. There are two small smd leds on the board. One burns when powered on. The second when charging. Soldered LEDs on wires instead of them and built them into the body of the charger.

Charging red is on. Since the red LED is more powerful than the green, while charging the green goes out and only the red remains lit, when the charging is over the red goes out and the green lights up.

Lithium batteries

Next I bought 10 lithium batteries and assembled the batteries in 2 parallel and then connected the 5 units in series. The batteries were connected by soldering with the pre-tempered copper plates. There’s one basic rule for soldering. Do not overheat the battery! So solder with a powerful soldering iron and as fast as possible in 1-2 seconds. If it did not work at once it is better to wait and not to boil the battery.

The consequences of overheating can lead to fire and burns. Be careful!

Who has a spot weld. There will be no problem with connection. As a result, the battery assembled at a voltage of 21 V and a capacity of 5.2 Ah. Connection of the battery to the control board is shown in the figure.

Then everything is packed in the case and tested under load.

I built an LM2596 module into the standard charger. The power supply should be a couple of volts more than the voltage of the charged battery. Set the voltage at idle 21 V. Then I connected the battery and set the charging current to 0,8 A. Why so? Because I have found the power supply unit for 24 V with maximal voltage of 25 V. at 0.8A. I did not need to buy it specially. It is better to charge longer. This is not a production version, but a home one.

While charging a small minus was revealed. When the battery is fully charged the charger should switch from CC phase to CV phase. That is, firstly the battery is charged with the current set (0,8A in my case), and when you reach 21V voltage is maintained at this level, and the current gradually drops to 0,1Iust (in my case 0,08A, set by the middle potentiometer). At this point the charging process stops. On this module the middle LED indicates this, but only signals that the battery is ready to work, but in fact charging continues, which is not critical in principle. The battery is not recharged anyway. And the problem is that because the control board has its own protection against overcharging, it shuts down the charger before it reaches the phase CV.

To get around this I had to lower the voltage of the charger module to about 20,7-20,8V. CV phase starts earlier, but in any case the battery is charged more fully than without it at all. If you don’t know about this little disadvantage, you won’t notice the difference in operation.

On the whole I like the finished device. Compared to what it used to be, it feels like this electric screwdriver. Specially for Radioscheme site. SssaHeKkk.

Forum for the discussion of the material FOR CHARGING THE SHURPPER FOR LITHUANIA BATTERIES

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How to rebuild and assemble?

Often a craftsman already has an old cordless electric screwdriver, which he is completely satisfied with. But the unit is equipped with outdated nickel cadmium batteries. Since the battery pack will still have to be replaced, there is a desire to replace the old battery with something newer. This will not only provide more comfortable work, but also save you from having to search the market for batteries of an obsolete model.

The simplest thing that comes to mind is to assemble in the housing of the old battery power unit from an electronic transformer. Now it is possible to use an electric screwdriver by connecting it to a household power supply.

14-volt models.4 volt can be connected to automotive batteries. If you assemble the adapter-extender with terminals or the cigarette lighter plug from an old battery case, you will get an indispensable device for garage or work “in the field”.

If we are converting an old battery pack to lithium, we can take into account the fact that lithium cells of the 18650 standard are extremely widespread on the market. Thus, we can make batteries for an electric screwdriver based on readily available parts

What’s more, the prevalence of the 18650 standard allows you to choose batteries from any manufacturer.

It is not difficult to open the case of an old battery and take out the old parts

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

Depending on the voltage for which the old battery was designed, you need 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 V instead of 1.2 В). So, each “lithium” cell replaces three “nickel” cells connected in series.

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

After you have managed to determine the number of consecutive stages, you will probably find that there is still room in the old case. This allows two cells to be joined in parallel in each stage, which doubles the capacity of the battery. To connect lithium batteries with each other in industries use nickel tape. Tape strips are joined together and to the lithium cells by means of contact welding. But soldering is quite acceptable at home.

Solder lithium cells with extreme care. The area to be joined should be thoroughly cleaned beforehand and a good flux should be applied. Soldering is done very quickly, with a well heated soldering iron of sufficiently high power.

Soldering itself is done by quickly and surely warming up the place where you connect the wire to the lithium element. To avoid the dangerous overheating of the cell, the duration of soldering must not exceed three to five seconds.

Good thing that nowadays you can buy prefabricated electronic control and balancing modules at fairly low prices. It is enough to choose the solution that is appropriate in your case. Basically, such controllers differ in the number of “steps” connected in series, the voltage between which must be equalized (balanced). In addition, they differ in the allowable load current and method of temperature control.

In any case, you can no longer charge a homemade lithium battery with the old charger for nickel batteries. They have fundamentally different charging algorithms and control voltages. You need a dedicated battery charger.

Which Lithium Battery to Choose?

In 7 out of 10 cases, 12-volt batteries are used for screwdrivers.

Voltage magnitude is a determining factor when choosing. It can be specified in the technical documentation to the device, on the Internet.

  • The value of the discharge current. Screwdrivers are powered by batteries with a high discharge current. Clarify the required parameter for a particular model can be in the technical documentation. It is a mistake to choose a battery only by its capacity, because the main parameter is the current. It can range from 15-30A, sometimes up to 40A.
  • Characteristics of Lithium-ion cells. Batteries of the 18650 standard should have the same capacity characteristics.
  • Number of new batteries. The calculation is easy to do. Ratio is as follows: 3 Ni-CDs equal 1 Li-ion. Replace the 12 volt old 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) will increase wear and tear of the equipment, will shorten the life of. But the power will increase. Therefore it is necessary to weigh up the pros and cons. You should not be in a hurry with the installation of sources in the tool. They need to be fully charged first.

Which BMS board is needed and how to connect it

Lithium batteries 18650 are afraid of overcharging and deep discharging. If cells are connected in series, synchronous operation of the cells cannot be guaranteed. If one bank has a lower capacity, it will replenish energy faster than the others when charging, and overcharging will occur during further charging. When working, a battery with a lower capacity will discharge faster than the others, which can lead to a deep discharge.

All of these problems can be solved by a protection board with balancing. BMS board:

  • protect against short circuits;
  • are restored after a protection trip;
  • monitor the voltage of each bank and switch off the load when at least one of the cells is completely discharged (deep discharge protection);
  • carry out the balancing (overcharge protection).

BMS board for an electric screwdriver must be able to withstand a maximum peak current of at least 30 A. in addition, the choice should be guided by the number of banks connected in series. 12 volt electric screwdriver requires 3 batteries, choose a 3S board. If you need a 14V supply, buy a 4S, and for 18V buy a 5S.

How to connect 2, 3 or 4 banks in series to a BMS board is shown in the picture.

Mixed, series-parallel connection can also be used. In this case connect the same number of batteries in parallel to the banks connected in series.

Charging device

What remains to be understood is how to charge the tool. It can not be connected to a standard power supply. A battery charger is needed.

In most cases the native accessories have no problem charging lithium batteries.

Charge comes through the controller. If the factory device is not suitable, it can be remade by installing the missing circuit components. This includes the charging stop nodes, protective components etc. The circuit is adjusted to the main determinant. the charging current.

If the circuit of the charger is thoroughly reworked it is not cost-effective to make an upgrade. It can easily be replaced with universal equipment or purchased new. Even with the purchase of the charger, the owner of an electric screwdriver acquires a powerful tool with extended battery life for a minimum price.

And how many batteries to buy?

A charged 18650 battery produces 4.2 volts. Divide the voltage from which the electric screwdriver works by 4.2 and round up (for a 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 pad that goes from the terminal to the battery, above the welding. Dispose of the removed battery at the designated point.


The project implies a quick removal of batteries (so that when the work is done, you can easily put them on a stationary charger, such as NITECORE I4 (On the website https://sdelaysam-svoimirukami.)), that’s why there were used holders of 2 x 18650 and how to build a budget charger for these batteries.

To reach the desired voltage it is necessary to connect the batteries in series (In this connection the plus of the battery is connected to the minus of the following one). As I used two holders, they need to be connected to each other to make a current exchange

The original holders wires were too thin, so they lost some heat and had to be rewired for bigger diameter to avoid this, taking into account the new battery setup.

for approximate indication of battery charge level a 12v LED connected in series with a 1kOhm current-limiting resistor was used.

Power LED should be brought out in parallel with the power supply of an electric screwdriver. To do this, the thick wires of the plus and minus of the battery block are soldered to a wire with a smaller cross section.

Wires with a larger cross section should be soldered to the terminals of the battery pack of an electric screwdriver, in my case they are put on a separate plate, and then, the plate is returned to its normal position, if desired, fixing glue.

To observe the LED in the case of the battery compartment is necessary to make a hole (this is well suited heated nail).

Since the LED serves as an indicator, but not as a lighting device, you can fix it in the hole, applying hot melt on it (this will make the glow softer). The photo of the electric screwdriver after recycling.

Note that for the batteries to work properly in series connection, they must be “married”, in other words, they must be from the same batch, the same capacity and model. If you follow this rule they will be discharged simultaneously. To check the charge of the batteries and prevent them from overdischarging. 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).