Conversion of an 18v screwdriver to lithium

Converting a screwdriver to lithium batteries 18650

Every craftsman is faced with the problem of reduced tool performance, or complete failure due to the battery. Manufacturers use nickel-cadmium batteries in 12, 14, 18-volt screwdrivers. The sequential assembly of several elements creates the required voltage. Replacing nickel-cadmium batteries with lithium batteries extends battery life by making the design lighter. Mandatory BMS board installation adds reliability. Therefore, the conversion of a screwdriver to lithium batteries, mainly to the 18650 form factor, is justified.

The meaning and procedure for converting screwdrivers to lithium batteries

Why do nickel cadmium batteries fail quickly? In a garland of series-connected cans, each one is special. The chemical process is individual, the charge in closed systems is different. In the event of a malfunction in one bank, the design does not provide the required voltage. The control system and charge balancing in individual components is not provided.

Each Ni-Cd bank provides 1.2V and Li-ion 18650 3.6V.
The capacity of a lithium battery is 2 times that of a nickel-cadmium battery, similar in size.
An overheated li-ion battery threatens an explosion and fire, therefore, the installation of control of the uniformity of the charge in the banks is mandatory. BMS is not installed in nickel-cadmium batteries. the manufacturer is not interested.
Lithium cells have no memory effect, unlike Ni-Cd, they can be charged at any time and within an hour.
The screwdriver becomes much easier after converting the battery to li-ion, using 18650 cells.

There are only two obstacles to converting a screwdriver for lithium batteries. it is impossible to work with it at minus. The capacity of cans decreases, starting from a decrease already from 10 0 C. Lithium batteries are expensive.

Knowing what input voltage is required for the screwdriver, the charger is reworked, taking into account the placement of the lithium battery cans and control elements in the factory container. You can also do with a flashlight by upgrading the socket for a block of 18650 cells.

Let’s say you need to rework a 12 V screwdriver using Ni-Cd cans on li-ion. If you use 3 cans, the output voltage is not enough: 3.6 x 3 = 10.8 V. With 4 components, the power of the apparatus will be higher: 3.6 x 4 = 14.4 V. This will make the instrument 182 g lighter. its power will increase slightly, capacity. solid pluses. But when dismantling, it is necessary to leave the terminals and the native thermal sensor.

Conversion of a screwdriver to lithium batteries 18650 14 V

When converting screwdrivers of different power and flashlights from Ni-Cd to Li-ion, batteries of the form factor 18650 are more often used. They easily fit into a container or a nest, since instead of two or three relatives, one lithium is installed. Alteration of the screwdriver battery should be carried out taking into account the peculiarities of lithium 18650 batteries.

This type of energy source does not tolerate deep discharge and excessive charge. Hence, it is necessary to use voltage control boards. Since each battery has its own character, their charge is corrected by a balancer. The point of reworking a screwdriver with a voltage of 14.4 V lies in creating a device using lithium batteries to facilitate a hand tool and increase its performance. Lithium 18650 batteries are most suitable for these purposes.

When selecting components, it should be taken into account that the starting current of the screwdriver is high, you must select the appropriate BMS for the required number of cans and at least 30 A. To convert the charging of the screwdriver to a lithium battery, you must stock up on a good soldering iron, non-acidic flux and thick wires to make jumpers.

Lithium-ion cans in the amount of 4 pcs.
4 cell li-ion battery controller, CF-4S30A-A works well. It has a built-in balancer that controls the charge of each element.
Hot melt glue, flux for soldering TAGS, solder.
Heat-resistant tape;
Connecting jumpers or thick insulated wire with a cross section of at least 0.75 squares, cut for bridges.

The procedure for converting a screwdriver for 18650:

Disassemble the case and remove a bundle of 12 Ni-Cd cells from the container.
Remove the garland, leaving the connector with the “” and “-” pins. Instead of a temperature sensor, a thermocouple from the controller will be installed.
Solder the assembly, considering that you cannot use acid, only neutral flux and pure solder. During the connection period, do not warm up the covers. Work pointwise.
Connect the balancing points to the controller according to the diagram. The board has connectors.
Connect assembly with plus and minus pins.
Check the functionality of the circuit. If everything works, assembled the battery, place the controller in the socket, secure with a sealant.

Lithium Battery BMS Nicd/Nimh Charger, Is it possible? Bosch cordless drill 14.4V PSR 1440

If the charger is not universal, additional alteration will be required. Screwdrivers for 12 V with a universal charger are assembled in the same way, but a protective circuit for connecting 3×18650 3.7 V for lithium batteries is used. In the same way, a screwdriver is reworked using a set of 18650 batteries in the amount of 2 elements.

Conversion of the Makita screwdriver to the lithium battery

There is a “Makita” screwdriver with a 1.3 A / h battery and a voltage of 9.6 V. To change the power source to a lithium-ion one, you will need 3 18650 components. The alteration will give the old tool new possibilities: it will increase the operating time on a single charge. will add power as the operating voltage rises to 10.8V.

The design will require the use of a BMS, a control controller that maintains the lithium cell operating mode within operating limits. With this breaker, each cell will be charged evenly without exceeding 4.2V, the lower voltage is 2.7V. The built-in balancer is used here.

The parameters of the controller should accompany the operation of the instrument when the operating current rises to 10-20 A. The Sony VTC4 30 A board, designed for a capacity of 2100 A / h, can ensure operation without shutdown. Of the 20 amperes, the Sanyo UR18650NSX accepting 2600A / h energies is suitable. The board is needed for 3 elements, which is marked in the 3S classification. In this case, the board must have 2 contacts, plus and minus. If the conclusions are designated with the letters “P-“, “P”, “C-“, they are intended for later models of screwdrivers.

Step-by-step instructions for converting a Makita screwdriver to lithium batteries looks like this.

It is possible to disassemble the battery with glue if you tap the junction with a soft-headed hammer on the weight. Direction of impact downward, butt-joint along the lower part of the body.
Take only the contact plates from the old assembly, carefully disconnecting them from the battery. The sensor and the breaker must be left.
Solder 3 elements in series using TAGS flux and insulated jumpers. The wire cross-section must be greater than 0.75 mm2.
Assemble the circuit with the controller, and connect the power supply to the contact connectors with 1.5 square wires.
Check the functionality of the circuit and reassemble the case by placing it on the glue again.

In a screwdriver with an old DC9710 charger, after charging the 18650 lithium battery, the red LED on the panel will turn off. The built-in controller monitors the charge level.

The Makita DC1414 T charger is used to charge 7.2-14.4 V power sources. While charging, the red light is on. But when charging a lithium battery, its voltage does not fit into the standards of salt products, and after 12 V the charger will flash red and green. But the necessary charging is already there. The screwdriver is ready to work.

Accumulators and batteries

Energy storage information website

Alteration of the “Hitachi” 12 V screwdriver for lithium batteries 18640

Features of reworking the 12 V Hitachi screwdriver for lithium batteries. The very compact battery compartment is designed for finger cells. Therefore, you should prepare a place for 18650 cells. It is necessary to cut one side of the partition in order to tightly place 1 element.

You need to get a gumboil, a flat metal connecting tape, hot glue. It is necessary to install lithium batteries in a screwdriver during rework through a protective controller. It should serve 3 18650 cells, 3.7V, and rated for 20-30 amps.

Remove the old battery from the socket, carefully disconnect the contacts in the assembly with the temperature sensor and the power indicator. Clean up and sign contacts. They should be brought out to one side, connected with solder to the leads from thick wires and filled with hot melt glue on the assembly.

Assemble a power source with one of the 3 cell controllers. Build a serial circuit of 3 Li-ion cells. Connect the controller. The conversion of the 12-volt lithium battery is completed when the structure is installed in the unit, secured, and the charging indicator lights up. After fully charging, the measurements show 12.17 volts in the external network. But this is enough for trouble-free long-term operation of the device.

Alteration of the Interskol screwdriver for lithium batteries 18650

Sooner or later, the nickel-cadmium assembly of 15 cans fails. One or two elements are lazy, and it is no longer possible to get the output voltage. Modern DSh “Interskol” on lithium batteries serve much better. Alteration of a screwdriver for 18 volt lithium batteries mastered by craftsmen.

It is necessary to purchase a protection board for 5S, 3.7 V and 40-50 A. You will need a balancing board and the energy sources themselves. 5 lithium 18650 batteries, you can leave them with factory thermistors by extending the wires. During installation, create a contact pad, insert the assembly, check the operability, secure. The assembly features of the wizard’s advice are given in detail in the video. See here for full details on reworking an 18-volt lithium screwdriver

Conversion to Makita lithium batteries

battery 1422, Ni-Cd 14.4V 2.0Ah
replacement for lithium cells, capacity: 2.0Ah, current output 20A
battery Makita PA14 14.4V 1.3Ah
MAKITA PA14 NiCd, 14.4V, 1.3Ah (repackaging Li-Ion 1.5Ah)
Screwdriver Makita 6270D 12V
Screwdriver Makita 6317D
Screwdriver Makita 6281D 14,4V
Screwdriver Makita 6260D 9.6V
Makita 6271D screwdriver, 12V battery
Screwdriver Makita 6337D, battery 14.4V
MAKITA PA12 NiCd, 12V, 1.3Ah (repackaged with Li-Ion 2.5Ah)
MAKITA PA12 NiCd, 12V, 1.3Ah (repackaging Li-Ion 1.5Ah)

Conversion to AEG lithium batteries

AEG BS 12X screwdriver, battery B1220 2,0Ah 12V
AEG B 1214G NiCd, 12V, 1.4Ah (repackaged with Li-Ion 1.5Ah)

Conversion to Sparki lithium batteries

battery Sparky BR 12E-B1HR 12 volt 1.5 Ah
battery Sparky BR 15E-B1HR NiCd 1,5Ah 14,4V
for Sparky professinal BR 15E 14.4V screwdriver
SPARKY BR12E-B1HR NiCd, 12V, 1.5Ah (repackaged for 1500mAh lithium)

Conversion to lithium batteries Sturm

battery for Sturm CD3012C screwdriver 12V 1.3Ah NiCd
NiCd cells were replaced with LiIon 18650 cells with a capacity of 5.2 Ah with the installation of a battery charge / discharge controller in the battery case. An additional charger is not required to charge the battery; you can use the standard charger to charge it. The controller does not allow the cells to be discharged below the threshold value and will not allow the cells to recharge above the norm.
battery for Sturm CD3014C screwdriver 14,4V 1.3Ah NiCd
battery for Sturm CD31181 18V 1.3Ah NiCd screwdriver
replaced the cells with lithium 18650. Inside the battery case, an assembly of 5 series Li-Ion 18650 cells plus a 5S charge / discharge controller is installed.
STORM 18V NiCd, 18V, 1.3Ah (repackaging for lithium 5s1p 2500mAh)

Conversion of Hitachi batteries to lithium

Cordless drill Hitachi DS 12DVF3 12V,
battery EB1214S 12V 1.4Ah (battery base height 40-45mm). Alteration is possible by removing the retaining lock. The battery holds well in the screwdriver body, we recommend using a rubber band or ring as additional fixation.
Cordless drill Hitachi DS12DVF3.
Battery AKKU BCC 1215 12v 1.5Ah (battery base height 50-53mm). Conversion is possible WITHOUT removing the locking lock.
HITACHI AKKU EB 1214 NiCd, 12V, 1.4Ah (repackaged to Li-Ion 3s1p 2.5Ah)
HITACHI AKKU EB 1414S NiCd, 14.4V, 1.4Ah (repackaged with Li-Ion 1.5Ah)
HITACHI AKKU EB 1814SL NiCd, 18V, 1.4Ah (repackaged for 2.5Ah lithium)

Conversion to Pitatel lithium batteries

battery Pitatel TSB-009-BOS18A-30M 18V 3.0Ah

Conversion to lithium batteries Interskol

battery for DA-12ER-01 (replacement for lithium cells, capacity 2.6 Ah)
battery for DA-14.4ER-F (replacement for lithium cells, capacity 2.5 Ah)

Conversion to Dorkel lithium batteries

Battery 18 Volt 1.3 Ah for the DORKEL DRA-18/2 drill Art.1428 Zip 116
replacement for lithium cells Samsung INR18650-20R 5S charge / discharge controller, capacity: 2.0Ah, current output 20A

Converting a screwdriver battery from Ni-Cd to Li-ion using a BMS protection board

Price: 3.50

Hello everyone, today I want to tell you about my next alteration of a home tool, without which any repair cannot do. This time I decided to remake my old, well-working Chinese Tandem screwdriver. It all started with the fact that native Ni-Cd batteries stopped not only holding a charge, but also being charged. It is not profitable to buy a new battery, it costs as much as a new inexpensive screwdriver with two Ni-Cd batteries. After reading some information on the Internet, it was decided to convert it to li-ion 18650 batteries, which have proven themselves well.

Having disassembled the Ni-Cd battery and throwing out the old batteries, leaving only a block with contacts for connecting to the screwdriver itself, I placed the batteries in the case. For ease of installation and ease of use, AB decided to install it in special slots. They can be easily inserted and also easily removed for charging in another charger, if the family will not charge them. Also, these batteries can be used in another device.

After completing the assembly, I started the screwdriver, worked with it a little and even tried to charge the AB with my own charger, in which there is no charge level control. After that, I had a question, how to control the state of the AB? To do this, I installed a small voltmeter and a shutdown button, which were also bought at Aliexpress. On the voltmeter it was possible to see the battery voltage and at the right time to put or remove from charging. And if you are not too lazy and unscrew the screws, then you can calibrate the capacity on the charger.

But, as I said above, the current consumption under heavy load is very large, and the contacts and wires in the slots are very thin and flimsy, the Chinese do not provide for soldering, everything is done on crimping. They were the first to not stand it and began to retreat and break off, the constant pulling out of the elements was not very convenient and not practical. Attempts to replace wires and strengthen contacts were in vain. After much torment, I decided to solder the battery with wires, and throw out the slots.

Also, to monitor the state of each element separately (charge and discharge voltages), I bought a BMS board for 5 AB on Ali with a voltage of 21V and a current of 100A. You will not be able to do without it if you go to get a high-quality battery, moreover, the price of the issue is not too high for such a rework. It can charge and discharge cells separately and monitor voltage and current. The dimensions of this board are such that they can be placed almost anywhere. The boards are available for a different number of elements. Soldering everything together and packing the batteries into the case with hot melt glue, everything worked out for me. The weight and charging time of the battery has decreased significantly, and the operating time has increased.

The board practically does not heat up. A couple of days later, one more revision had to be made, since the button could not withstand the working current of the screwdriver and burned out. It was replaced with a new one and a 12V, 40A automotive relay was added. The relay allowed to unload the power button, but added temperature. As it turned out, it heats up quite a lot with a long operating time.

In the end, I want to say that the most important part of my rework is the BMS board. You cannot do without it, since it is impossible to control the charge and discharge of li-ion batteries in another way. And overcharging and overheating of the battery is very dangerous and can lead to a fire.

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.

Conversion of a screwdriver to lithium batteries 18650 14 V

Lithium-ion cans in the amount of 4 pcs.
4 cell li-ion battery controller, CF-4S30A-A works well. It has a built-in balancer that controls the charge of each element.
Hot melt glue, flux for soldering TAGS, solder.
Heat-resistant tape;
Connecting jumpers or thick insulated wire with a cross section of at least 0.75 squares, cut for bridges.

The procedure for converting a screwdriver for 18650:

Disassemble the case and remove a bundle of 12 Ni-Cd cells from the container.
Remove the garland, leaving the connector with the “” and “-” pins. Instead of a temperature sensor, a thermocouple from the controller will be installed.
Solder the assembly, considering that you cannot use acid, only neutral flux and pure solder. During the connection period, do not warm up the covers. Work pointwise.
Connect the balancing points to the controller according to the diagram. The board has connectors.
Connect assembly with plus and minus pins.
Check the functionality of the circuit. If everything works, assembled the battery, place the controller in the socket, secure with a sealant.

Energy storage information website

Every craftsman is faced with the problem of reduced tool performance, or complete failure due to the battery. Manufacturers use nickel-cadmium batteries in 12, 14, 18 volt screwdrivers. The sequential assembly of several elements creates the required voltage. Replacing nickel-cadmium batteries with lithium batteries extends battery life by making the design lighter. Mandatory BMS board installation adds reliability. Therefore, the conversion of a screwdriver to lithium batteries, mainly to the 18650 form factor, is justified.

The meaning and procedure for converting screwdrivers to lithium batteries

Each Ni-Cd bank provides 1.2V and Li-ion 18650 3.6V.
The capacity of a lithium battery is 2 times that of a nickel-cadmium battery, similar in size.
An overheated li-ion battery threatens an explosion and fire, therefore, the installation of control of the uniformity of the charge in the banks is mandatory. BMS is not installed in nickel-cadmium batteries. the manufacturer is not interested.
Lithium cells have no memory effect, unlike Ni-Cd, they can be charged at any time and within an hour.
The screwdriver becomes much easier after converting the battery to li-ion, using 18650 cells.

Alteration of the Interskol screwdriver for lithium batteries 18650

It is necessary to purchase a protection board for 5S, 3.7 V and 40-50 A. You will need a balancing board and the energy sources themselves. 5 lithium 18650 batteries, you can leave them with factory thermistors by extending the wires. During installation, create a contact pad, insert the assembly, check the operability, secure. The assembly features of the wizard’s advice are given in detail in the video. See here for full details on reworking an 18-volt lithium screwdriver

If you have (or have been lying around with friends) an old Ni-Cd screwdriver and all the batteries have sat down, and even the charger has broken down (burned out), order an MT3608 board on Ali for 40r, look for an old charger from a cell phone (all in bulk) and old laptop batteries (of which we need Li-Ion 18650 batteries).

Today we will be converting an old screwdriver from nickel-cadmium batteries to lithium-ion batteries, and, accordingly, its charger.

Everything is easily redone. Let’s start with batteries.

If the screwdriver was at 12V, we will need 4 18650 batteries (16.8V maximum), if at 14.4V. 5 pcs (21V maximum), if at 18V. then 6 pcs (25.2V maximum). The safety margin of the electric motor and other mechanisms in the screwdriver is large, and we will not be in the way of increasing the power.

First, 18650 Li-Ion batteries are tested, if there is anything to choose from, they are selected with the same capacity. Expensively and accurately, this can be done using a BT-C3100 V2.2 device or similar. The approximate capacity of 18650 batteries from laptops is 1800-2200 mAh, sometimes you need to divide by 2 the capacity written on the battery case. And so it is enough to charge Li-Ion 18650 batteries up to 4.2V in any charging suitable for them with a voltage limitation, give the same load and after the same time measure the voltage on them. If it fell to the same values, then it is normal. For example, we load a fully charged 18650 on a 12V lamp from a car, and after a minute we measure how much is left of 4.2V. If about the same, the batteries are suitable.

We throw out the old dead / closed Ni-Cd batteries from the body of the replaceable battery, and instead of them we solder Li-Ion to the voltage we need. For the Li-Ion batteries themselves, it is better to leave flat connectors from the laptop, but if you still solder the wires to the Li-Ion, cool the soldering place by blowing, solder quickly with flux or acid to reduce the heating time of the battery surfaces, in order to avoid damage. Take wires for soldering from an old computer PSU, or thicker.

We check how the screwdriver turns, usually this is an increase in power by 20-40% and a decrease in the weight of a replaceable battery.

Now we turn to reworking the charging, especially if it burned out or not. They are different for different companies, Bosch, Shturm, Hitachi, everything is different. From the charging case, you can get all the stuffing, except for the terminal block. By and large, we only need a terminal block to connect a removable battery. Of course, everything will be better in the case. I had too much current from a heavy transformer, and it was heavy, so I found a better use for it (in a laboratory PSU).

We solder the output of the charger for the cell to the MT3608 board on the VIn contacts, plus, minus. We turn on, tighten the resistor to the output voltage we need, this is 16.8, 21 or 25.2V, respectively, what kind of Li-Ion battery you have.

MT3608 is a Step Up (boost) voltage converter with pulse width modulation, on ordinary boards, the output capacitor must be soldered to the large contact of the VOut output and accordingly cleaned the ground next to it to solder the capacitor. This is a deficiency of the Chinese, the board works worse from the factory.

We limit the charge current, for this we need a 5-15 Ohm resistor and the simplest and smallest diode. Solder the VOut plus wire directly to the battery plus terminal block. And VOut- through a resistor in the negative wire. From the measuring point of the resistor, we solder the diode (anode) (cathode with a strip) to the FB signal of the microcircuit, this is the 3rd contact of MT3608, fine, but it rings out on the potentiometer on the other side of the board, which is much easier to solder.

We connect the battery for charging and check the charge current, it will be from 50 mA (15 ohms) to 200 mA (5 ohms). Accordingly, the current from the cellular charging will be, for example, 50mA (21V / 5V / efficiency) = 300mA, and for 200mA (21V / 5V / efficiency) = 1200mA (it may be too large, not every cellular charging will pull it). We check the charging, if it heats up or the voltage from it sags from 5V to 2.5V, then the current should be reduced to avoid overheating.

You may ask why such a small charging current, because it will take a long time to charge. The first moment, at high charge currents, close to 1.0C (C-capacity of the Li-Ion battery), the charge time is about an hour, the battery will definitely die after 1-2 years of such atrocities. Second, even old Li-Ion batteries tend to recover at low charging currents (unless, of course, chemistry leaks and swells), and charging with a low current will definitely prolong the life of the battery.

Cons: Long full charge time (10-20 hours). It is extremely undesirable to plant Li-Ion batteries below 3V per cell, that is, to do a full discharge (when the screwdriver turns much weaker), Li-Ion batteries lose their capacity much earlier in the cold, already at 0 degrees the screwdriver will work little (You can wear a glove or a scarf or a scarf only for the battery of a screwdriver for short-term work in the cold, or only warm up the battery in a room on a heating battery).

Somehow I came across a very weak Chinese cell phone charger. Written 5V, 450mA. Even at 21V 50mA, MT3608 overloaded charging and the output voltage dropped to 2V, charging boiled. What had to be redone:

DeWalt 18V XRP Conversion to 20V Lithium ION

First, I made a voltage limitation for the start of the conversion Uin for the MT3608 (so that the converter does not transfer the charger power supply to the 2V 2A state, when everything starts to get very hot and burn). In a diagram of simple parts, the resistor R2 can be replaced with a 1-10-100kΩ trimmer (10k is optimal and R1 is 10k then). This made it possible to start the StepUp converter only from the increased input voltage, the maximum current for Chinese charging was at a voltage of 4.3 V, if you slightly increase the trimmer, the converter stopped and the voltage jumped to 5V.

I also wanted to raise the charging current, 21V 80 mA was not enough.

The higher the voltage on the secondary winding of the high-frequency transformer of the charging power supply converter, the more power can be removed at the same current (and the maximum current depends on the wire cross-section), but you can reach oversaturation or overheating of the transformer, and the power supply circuit can go into protection or burn out.

At the output of the charging PSU, there is a feedback optocoupler and a 3-4 Volt Zener diode or resistors to stabilize 5.2V. I was lucky and came across a charger, including a 7.5V protective zener diode, which I soldered instead of a measuring zener diode, and received 9V at the charger output. Above 10V, it is better not to overclock a charger for a cell phone, usually at 11-12 volts stabilization breaks down.

As a result, I tightened the limitation of input voltage consumption by 8.2 volts, received 21V 140mA at the output of the converter, as a result, 13 hours of charge for my 1800mAh 18650 batteries is normal.

Tags: from scrap parts, can be found everywhere, readily available, easy to alter, simplicity, easier when there is nothing.

Leave comments, share your experience, advise who got what, how best to redo it. If you shoot a video of the rework, post a link here.

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).

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 disconnected. At the same time, the case is not damaged in any way, I have already disassembled 4 pieces this way.

The part of interest to us.

From the old circuit, only contact plates are needed. They are permanently spot welded to the top 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.

Alteration of the “Hitachi” 12 V screwdriver for lithium batteries 18640

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 ones, 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.

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 will be 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 30-amp 18650 cells made by Sony VTC4 (2100 mAh capacity) and 20-amp Sanyo UR18650NSX (2600 mAh capacity). They work fine in my 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 assemble 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”.

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.

Sources:

http://www.cleon.ru/repair-battery-to-liion-for-power-tools.php
http://skustore.ru/blog/aliexpress/1398.html
http://morflot.su/peredelka-shurupoverta-18v-na-litij/