Lithium batteries (Li-Io, Li-Po) are the most popular rechargeable sources of electrical energy at the moment. The lithium battery has a nominal voltage of 3.7 Volts, which is indicated on the case. However, a 100% charged battery has a voltage of 4.2 V, and a discharged one “to zero” has a voltage of 2.5 V. There is no point in discharging the battery below 3 V, firstly, it will deteriorate, and secondly, in the range from 3 to 2.5 It only supplies a couple of percent of energy to the battery. Thus, the operating voltage range is 3 – 4.2 Volts. You can watch my selection of tips for using and storing lithium batteries in this video
There are two options for connecting batteries, series and parallel.
With a series connection, the voltage on all batteries is summed up, when a load is connected, a current flows from each battery equal to the total current in the circuit; in general, the load resistance sets the discharge current. You should remember this from school. Now comes the fun part, capacity. The capacity of the assembly with this connection is fairly equal to the capacity of the battery with the smallest capacity. Let's imagine that all batteries are 100% charged. Look, the discharge current is the same everywhere, and the battery with the smallest capacity will be discharged first, this is at least logical. And as soon as it is discharged, it will no longer be possible to load this assembly. Yes, the remaining batteries are still charged. But if we continue to remove current, our weak battery will begin to overdischarge and fail. That is, it is correct to assume that the capacity of a series-connected assembly is equal to the capacity of the smallest or most discharged battery. From here we conclude: to assemble a series battery, firstly, you need to use batteries of equal capacity, and secondly, before assembly, they all must be charged equally, in other words, 100%. There is such a thing called BMS (Battery Monitoring System), it can monitor each battery in the battery, and as soon as one of them is discharged, it disconnects the entire battery from the load, this will be discussed below. Now as for charging such a battery. It must be charged with a voltage equal to the sum of the maximum voltages on all batteries. For lithium it is 4.2 volts. That is, we charge a battery of three with a voltage of 12.6 V. See what happens if the batteries are not the same. The battery with the smallest capacity will charge the fastest. But the rest have not yet charged. And our poor battery will fry and recharge until the rest are charged. Let me remind you that lithium also does not like overdischarge very much and deteriorates. To avoid this, recall the previous conclusion.
Let's move on to parallel connection. The capacity of such a battery is equal to the sum of the capacities of all batteries included in it. The discharge current for each cell is equal to the total load current divided by the number of cells. That is, the more Akum in such an assembly, the more current it can deliver. But an interesting thing happens with tension. If we collect batteries that have different voltages, that is, roughly speaking, charged to different percentages, then after connecting they will begin to exchange energy until the voltage on all cells becomes the same. We conclude: before assembling, the batteries must again be charged equally, otherwise, when connected, large currents will flow, and the discharged battery will be damaged, and most likely may even catch fire. During the discharge process, the batteries also exchange energy, that is, if one of the cans has a lower capacity, the others will not allow it to discharge faster than themselves, that is, in a parallel assembly you can use batteries with different capacities. The only exception is operation at high currents. On different batteries under load, the voltage drops differently, and current will start flowing between the “strong” and “weak” batteries, and we don’t need this at all. And the same goes for charging. You can absolutely safely charge batteries of different capacities in parallel, that is, balancing is not needed, the assembly will balance itself.
In both cases considered, the charging current and discharge current must be observed. The charging current for Li-Io should not exceed half the battery capacity in amperes (1000 mah battery - charge 0.5 A, 2 Ah battery, charge 1 A). The maximum discharge current is usually indicated in the datasheet (TTX) of the battery. For example: 18650 laptops and smartphone batteries cannot be loaded with a current exceeding 2 battery capacities in Amperes (example: a 2500 mah battery, which means the maximum you need to take from it is 2.5 * 2 = 5 Amps). But there are high-current batteries, where the discharge current is clearly indicated in the characteristics.
Features of charging batteries using Chinese modules
Standard purchased charging and protection module for 20 rubles for lithium battery ( link to Aliexpress)
(positioned by the seller as a module for one 18650 can) can and will charge any lithium battery, regardless of shape, size and capacity to the correct voltage of 4.2 volts (the voltage of a fully charged battery, to capacity). Even if it is a huge 8000mah lithium package (of course we are talking about one 3.6-3.7v cell). The module provides a charging current of 1 ampere, this means that they can safely charge any battery with a capacity of 2000mAh and above (2Ah, which means the charging current is half the capacity, 1A) and, accordingly, the charging time in hours will be equal to the battery capacity in amperes (in fact, a little more, one and a half to two hours for every 1000mah). By the way, the battery can be connected to the load while charging.
Important! If you want to charge a smaller capacity battery (for example, one old 900mAh can or a tiny 230mAh lithium pack), then the charging current of 1A is too much and should be reduced. This is done by replacing resistor R3 on the module according to the attached table. The resistor is not necessarily smd, the most ordinary one will do. Let me remind you that the charging current should be half the battery capacity (or less, no big deal).
But if the seller says that this module is for one 18650 can, can it charge two cans? Or three? What if you need to assemble a capacious power bank from several batteries?
CAN! All lithium batteries can be connected in parallel (all pluses to pluses, all minuses to minuses) REGARDLESS OF CAPACITY. Batteries soldered in parallel maintain an operating voltage of 4.2v and their capacity is added up. Even if you take one can at 3400mah and the second at 900, you will get 4300. The batteries will work as one unit and will discharge in proportion to their capacity.
The voltage in a PARALLEL assembly is ALWAYS THE SAME ON ALL BATTERIES! And not a single battery can physically discharge in the assembly before the others; the principle of communicating vessels works here. Those who claim the opposite and say that batteries with a lower capacity will discharge faster and die are confused with SERIAL assembly, spit in their faces.
Important! Before connecting to each other, all batteries must have approximately the same voltage, so that at the time of soldering, equalizing currents do not flow between them; they can be very large. Therefore, it is best to simply charge each battery separately before assembly. Of course, the charging time of the entire assembly will increase, since you are using the same 1A module. But you can parallel two modules, obtaining a charging current of up to 2A (if your charger can provide that much). To do this, you need to connect all similar terminals of the modules with jumpers (except for Out- and B+, they are duplicated on the boards with other nickels and will already be connected anyway). Or you can buy a module ( link to Aliexpress), on which the microcircuits are already in parallel. This module is capable of charging with a current of 3 Amps.
Sorry for the obvious stuff, but people still get confused, so we'll have to discuss the difference between parallel and serial connections.
PARALLEL connection (all pluses to pluses, all minuses to minuses) maintains the battery voltage of 4.2 volts, but increases the capacity by adding all the capacities together. All power banks use parallel connection of several batteries. Such an assembly can still be charged from USB and the voltage is raised to an output of 5v by a boost converter.
CONSISTENT connection (each plus to minus of the subsequent battery) gives a multiple increase in the voltage of one charged bank 4.2V (2s - 8.4V, 3s - 12.6V and so on), but the capacity remains the same. If three 2000mah batteries are used, then the assembly capacity is 2000mah.
Important! It is believed that for sequential assembly it is strictly necessary to use only batteries of the same capacity. Actually this is not true. You can use different ones, but then the battery capacity will be determined by the SMALLEST capacity in the assembly. Add 3000+3000+800 and you get an 800mah assembly. Then the specialists begin to crow that the less capacious battery will then discharge faster and die. But it doesn’t matter! The main and truly sacred rule is that for sequential assembly it is always necessary to use a BMS protection board for the required number of cans. It will detect the voltage on each cell and turn off the entire assembly if one discharges first. In the case of an 800 bank, it will discharge, the BMS will disconnect the load from the battery, the discharge will stop and the residual charge of 2200mah on the remaining banks will no longer matter - you need to charge.
The BMS board, unlike a single charging module, IS NOT A sequential charger. Needed for charging configured source of the required voltage and current. Guyver made a video about this, so don’t waste your time, watch it, it’s about this in as much detail as possible.
Is it possible to charge a daisy chain assembly by connecting several single charging modules?
In fact, under certain assumptions, it is possible. For some homemade products, a scheme using single modules, also connected in series, has proven itself, but EACH module needs its own SEPARATE POWER SOURCE. If you charge 3s, take three phone chargers and connect each to one module. When using one source - power short circuit, nothing works. Such a system also works as protection for the assembly (but the modules are capable of delivering no more than 3 amperes). Or, simply charge the assembly one by one, connecting the module to each battery until fully charged.
Battery charge indicator
Another pressing problem is to at least know approximately how much charge remains on the battery so that it does not run out at the most crucial moment.
For parallel 4.2-volt assemblies, the most obvious solution would be to immediately purchase a ready-made power bank board, which already has a display showing charge percentages. These percentages aren't super accurate, but they still help. The issue price is approximately 150-200 rubles, all are presented on the Guyver website. Even if you are not building a power bank but something else, this board is quite cheap and small to fit into a homemade product. Plus, it already has the function of charging and protecting batteries.
There are ready-made miniature indicators for one or several cans, 90-100 rubles
Well, the cheapest and most popular method is to use an MT3608 boost converter (30 rubles), set to 5-5.1v. Actually, if you make a power bank using any 5-volt converter, then you don’t even need to buy anything additional. The modification consists of installing a red or green LED (other colors will work at a different output voltage, from 6V and higher) through a 200-500 ohm current-limiting resistor between the output positive terminal (this will be a plus) and the input positive terminal (for an LED this will be a minus). You read that right, between two pluses! The fact is that when the converter operates, a voltage difference is created between the pluses; +4.2 and +5V give each other a voltage of 0.8V. When the battery is discharged, its voltage will drop, but the output from the converter is always stable, which means the difference will increase. And when the voltage on the bank is 3.2-3.4V, the difference will reach the required value to light the LED - it begins to show that it is time to charge.
How to measure battery capacity?
We are already accustomed to the opinion that for measurements you need an Imax b6, but it costs money and is redundant for most radio amateurs. But there is a way to measure the capacity of a 1-2-3 can battery with sufficient accuracy and cheaply - a simple USB tester.
Modern electronic devices (such as cell phones, laptops or tablets) are powered by lithium-ion batteries, which have replaced their alkaline counterparts. Nickel-cadmium and nickel-metal hydride batteries have given way to Li─Ion batteries due to the better technical and consumer qualities of the latter. The available charge in such batteries from the moment of production ranges from four to six percent, after which it begins to decrease with use. During the first 12 months, battery capacity decreases by 10 to 20%.
Original chargers
Charging units for ion batteries are very similar to similar devices for lead-acid batteries, however, their batteries, called “banks” for their external similarity, have a higher voltage, so there are more stringent tolerance requirements (for example, the permissible voltage difference is only 0. 05 c). The most common format of a 18650 ion battery bank is that it has a diameter of 1.8 cm and a height of 6.5 cm.
On a note. A standard lithium-ion battery requires up to three hours to charge, and the more precise time is determined by its original capacity.
Manufacturers of Li-ion batteries recommend using only original chargers for charging, which are guaranteed to provide the required voltage for the battery and will not destroy part of its capacity by overcharging the element and disrupting the chemical system; it is also undesirable to fully charge the battery.
Note! During long-term storage, lithium batteries should optimally have a small (no more than 50%) charge, and it is also necessary to remove them from the units.
If lithium batteries have a protection board, then they are not in danger of being overcharged.
The built-in protection board cuts off excessive voltage (more than 3.7 volts per cell) during charging and turns off the battery if the charge level drops to a minimum, usually 2.4 volts. The charge controller detects the moment when the voltage on the bank reaches 3.7 volts and disconnects the charger from the battery. This essential device also monitors the temperature of the battery to prevent overheating and overcurrent. The protection is based on the DV01-P microcircuit. After the circuit is interrupted by the controller, its restoration is carried out automatically when the parameters are normalized.
On the chip, a red indicator means charge, and green or blue indicates that the battery is charged.
How to properly charge lithium batteries
Well-known manufacturers of li-ion batteries (for example, Sony) use a two- or three-stage charging principle in their chargers, which can significantly extend the battery life.
At the output, the charger has a voltage of five volts, and the current value ranges from 0.5 to 1.0 of the nominal capacity of the battery (for example, for an element with a capacity of 2200 milliamp-hours, the charger current should be from 1.1 amperes.)
At the initial stage, after connecting the charger for lithium batteries, the current value is from 0.2 to 1.0 of the nominal capacity, while the voltage is 4.1 volts (per cell). Under these conditions, the batteries charge in 40 to 50 minutes.
To achieve constant current, the charger circuit must be able to raise the voltage at the battery terminals, at which time the charger for most lithium-ion batteries acts as a conventional voltage regulator.
Important! If it is necessary to charge lithium-ion batteries that have a built-in protection board, then the open circuit voltage should not be more than six to seven volts, otherwise it will deteriorate.
When the voltage reaches 4.2 volts, the battery capacity will be between 70 and 80 percent capacity, which will signal the end of the initial charging phase.
The next stage is carried out in the presence of constant voltage.
Additional Information. Some units use a pulse method for faster charging. If the lithium-ion battery has a graphite system, then they must comply with the voltage limit of 4.1 volts per cell. If this parameter is exceeded, the energy density of the battery will increase and trigger oxidation reactions, shortening the life of the battery. In modern battery models, special additives are used that allow the voltage to be increased when connecting a charger for li ion batteries to 4.2 volts plus/minus 0.05 volts.
In simple lithium batteries, chargers maintain a voltage level of 3.9 volts, which for them is a reliable guarantee of long service life.
When delivering a current of 1 battery capacity, the time to obtain an optimally charged battery will be from 2 to 3 hours. As soon as the charge becomes full, the voltage reaches the cutoff norm, the current value rapidly drops and remains at the level of a couple of percent of the initial value.
If the charging current is artificially increased, the time of use of the charger to power lithium-ion batteries will hardly decrease. In this case, the voltage initially increases faster, but at the same time the duration of the second stage increases.
Some chargers can fully charge the battery in 60-70 minutes; during such charging, the second stage is eliminated, and the battery can be used after the initial stage (the charging level will also be at 70 percent capacity).
At the third and final charging stage, a compensating charge is carried out. It is not carried out every time, but only once every 3 weeks, when storing (not using) batteries. In battery storage conditions, it is impossible to use jet charging, because in this case lithium metallization occurs. However, short-term recharging with constant voltage current helps to avoid charge losses. Charging stops when the voltage reaches 4.2 volts.
Lithium metallization is dangerous due to the release of oxygen and a sudden increase in pressure, which can lead to ignition and even explosion.
DIY battery charger
A charger for lithium-ion batteries is inexpensive, but if you have a little knowledge of electronics, you can make one yourself. If there is no accurate information about the origin of the battery elements, and there are doubts about the accuracy of the measuring instruments, you should set the charge threshold in the region from 4.1 to 4.15 volts. This is especially true if the battery does not have a protective board.
To assemble a charger for lithium batteries with your own hands, one simplified circuit is enough, of which there are many freely available on the Internet.
For the indicator, you can use a charging type LED, which lights up when the battery charge is significantly reduced, and goes out when discharged to “zero”.
The charger is assembled in the following order:
- a suitable housing is located;
- a five-volt power supply and other circuit parts are mounted (strictly follow the sequence!);
- a pair of brass strips is cut out and attached to the socket holes;
- using a nut, the distance between the contacts and the connected battery is determined;
- A switch is installed to change the polarity (optional).
If the task is to assemble a charger for 18650 batteries with your own hands, then a more complex circuit and more technical skills will be required.
All lithium-ion batteries require recharging from time to time, however, overcharging as well as completely discharging should be avoided. Maintaining the functionality of batteries and maintaining their working capacity for a long time is possible with the help of special chargers. It is advisable to use original chargers, but you can assemble them yourself.
Video
I made myself a charger for four lithium-ion batteries. Someone will now think: well, he did it and did it, there are plenty of them on the Internet. And I want to say right away that my design is capable of charging either one battery or four at once. All batteries are charged independently of each other.
This makes it possible to simultaneously charge batteries from different devices and with different initial charges.
I made a charger for 18650 batteries, which I use in a flashlight, powerbanks, laptop, etc.
The circuit consists of ready-made modules and is assembled very quickly and simply.
Will need
- - 4 things.
- - 4 things.
- Paper clips.
Manufacturing a charger for different numbers of batteries
First we'll make the battery compartment. To do this, we take a universal circuit board with a large number of holes and ordinary paper clips.
We bite off these corners from the paper clips.
We insert it into the board, having previously tried on the length of the batteries you need. Because such a charger can be made not only for 18650 batteries.
We solder parts of the paper clips to the bottom of the board.
Then we take the charging controllers and place them on the remaining space on the board, preferably opposite each battery.
The charging controller will be mounted on these legs, made from a PLS connector.
Solder the module on top and to the board below. These legs will carry the power current to the module and the charging current to the batteries.
Four sections are ready.
Next, to switch charging points, we will install buttons or toggle switches.
The whole thing connects like this:
You may ask - why are there only three buttons and not four? And I will answer - since one module will always work, because one battery will always be charged, otherwise there is no point in plugging in a charger at all.
We solder the conductive tracks.
The result is that with buttons you can connect a place to charge from 1 to 4 batteries.
An LED is installed on the charge module, which indicates that the battery that is being charged from it is charged or not.
I assembled the entire device in half an hour. It is powered by a 5-volt power supply (adapter), which, by the way, also needs to be chosen wisely so that it charges all four batteries at once. The entire circuit can also be powered from a USB computer.
We connect the adapter to the first module, and then turn on the necessary buttons and the voltage from the first module will go to other places, depending on the switches that are turned on.
Li-ion batteries of the 18650 type of various capacities are now very widespread. With their acquisition, the problem of charging arises and must comply with the technical requirements for the charging process. Here are some of these requirements:
- charging with stable current;
- voltage stabilization mode;
- indication of the end of charging;
- not exceeding the permissible temperature during battery charging.
We present to your attention a Li-ion battery charger circuit that is easy to manufacture and set up and has proven itself in operation.
The circuit is a current and voltage stabilizer. Until the voltage on the battery during charging reaches the level Ustabil.=(R7/R5+1)*Uref (Uref-reference voltage TL431=2.5V), TL431 is in the closed state, and the circuit works as a current stabilizer. Ist.=0.6/R2 (0.6 is the opening voltage of the KT816V transistor). As soon as the voltage on the battery reaches Ustabil., the circuit goes into voltage stabilization mode. For a Li-ion battery, this value is 4.2V. When the battery voltage reaches 4.2V, the yellow LED starts to light up, indicating that the battery is 80-90% charged. The charging current decreases to 7...8mA. Leave the battery in this state for 10-15 hours until it reaches its full capacity.
A little about the purpose of the circuit elements.
LED1 - blue, lights up when the battery (AC) is installed in the charging box and the charger power is not connected. When the voltage across the battery is less than 3V, LED1 does not light up.
LED2 - yellow. Serves to indicate the end of the battery charging process. When an uncharged AK is placed in the box, LED2 does not light up. If it lights up, then this indicates that a charged AK is inserted into the box (with the charger power not connected).
R2 - limits the charging current of the AK.
R5, R7 - serve to set the voltage to 4.2V on the contacts of the charging box before installing the battery in it (any one can be used).
All charger parts, except the transistor, are installed on the printed circuit board on the side of the printed conductors:
Board option for those who are not lazy to drill holes in fiberglass:
The transistor is equipped with a small heatsink. During charging, the transistor heats up to 40°C. Resistor R2 also heats up, so it is better to install two 10 Ohm resistors in parallel to reduce heating.
The power supply voltage for charging one battery is approximately 5V DC. If it is necessary to charge several batteries at once, the power supply voltage is selected so that it is 4.2V on each unit. The power of the power supply is selected from the charging current for each battery. You can use a switching power supply. The dimensions of the charger will be smaller.
The process of setting up the charger is simple. Without inserting the battery, we supply power to the circuit. Both LEDs should light up. Next, we measure the voltage at the contacts of the charging box. If it is 4.2V, you are in luck and the setup is almost complete. If the voltage is more or less than 4.2V, turn off the power, instead of resistor R5 or R7, solder in a variable multi-turn resistor 10k and precisely set the voltage to 4.2V on the contacts of the box. Having measured the value of the resulting resistance of the adjustable resistor, we select the same constant and solder it into the circuit. Once again, check the voltage at the contacts of the charging box. We check the amount of charging current with an ammeter at the contacts of the charging box without inserting the battery. By selecting the value of resistor R2, you can set the desired charging current. We don’t get carried away with high currents; the battery may heat up, which is absolutely unacceptable. Overheating causes the capacity of Li-ion batteries to decrease and not be restored.
It is best to charge batteries one at a time. If you need to charge several batteries simultaneously, you can connect the blocks in series according to this scheme.
In this scheme, each battery is charged separately. The voltage at the end of charging on each battery will be 4.2V, and the charging current will be 0.5A. When charging, for example, seven batteries simultaneously, the power source voltage should be 4.2V*7=29.5V. The power of the power source is determined by the charging current of 0.5A for each battery, i.e. approximately 40W.
Photo of the finished device.
Charger for a screwdriver - how to choose and whether you can make it yourself
Screwdrivers are found in everyone where simple repairs are made. Any electrical appliance requires stationary electricity, or in other words, a power supply. Since cordless screwdrivers are very necessary, an additional charger is required.
It comes complete with a drill, so no electrical appliance can fail. So that you do not encounter the problem of non-working equipment, we will study the general description of chargers for a screwdriver.
Types of chargers
Analog with built-in power supply
Their popularity is justified by their low price. If a drill (screwdriver) is not designed for professional use, the duration of work is not the first issue. Benefits of automation. Do-it-yourself automated ice drill from a screwdriver has a number of advantages. The task of a conventional charger is to obtain a constant voltage with a current load sufficient to charge the battery.
This type of charging works following the principle of an ordinary stabilizer. For example, let's look at the circuit of a charger for a 9-11 volt battery. The type of batteries does not matter.
Such a power supply (aka charger) can be assembled their hands. It is natural to solder the circuit on a universal circuit board. To dissipate the heat of the stabilizer chip, a copper radiator with an area of 20 cm² is sufficient.
The input transformer (Tr1) reduces the 220 volt AC voltage to 20 volts. The power of the transformer is calculated based on the current and voltage at the output of the charger. Next, the alternating current is rectified using the diode bridge VD1. Typically, the Russian automobile industry (especially the Chinese) use an assembly of Schottky diodes.
After rectification, the current will pulsate, which is detrimental to the production performance of the circuit. The ripples are smoothed out by a filtering electrolytic capacitor (C1).
The role of the stabilizer is performed by the KR142EN microcircuit, or “krenka” in amateur radio slang. To obtain a voltage of 12 volts, the microcircuit index must be 8B. The control is assembled on a transistor (VT2) not trimming resistors.
Automation is not provided on similar devices; the battery charging time is determined by the user. To control the charge, a lightweight circuit has been assembled using a transistor (VT1) and a diode (VD2). When the charging voltage is reached, the indicator (LED HL1) goes out.
More advanced systems include a switch that turns off the voltage at the end of the charge in the form of an electronic key.
Read also
Included with economy class screwdrivers (manufactured in the Middle Kingdom), there are no more ordinary chargers. It’s not surprising that the failure rate is quite high. The owner faces the prospect of being left with a relatively new, inoperable screwdriver. Using the attached diagram, you can assemble a charger for a screwdriver without the help of others, which will last longer than the factory one. Technology for laying paving slabs step by step planning. At this stage, you should decide on the future site for laying paving slabs with your own hands and create a plan for it. By changing the transformer not the stabilizer, you can easily select the desired value for your battery.
Analog with external power supply
Let's move on to heavy weapons. Professional screwdrivers are used intensively, and downtime due to a low battery is unacceptable. We leave out the price issue; any serious equipment is expensive. Moreover, the kit usually includes two batteries. While one is in work, the second is being recharged.
A switching power supply, complete with an intelligent charge control circuit, fills the battery 100% in literally 1 hour. You can also assemble an analog charger with the same power. But its weight and dimensions will be comparable to a screwdriver.
Pulse chargers do not have all these disadvantages. Compact size, high charge currents, thoughtful protection. There is only one problem: the complexity of the scheme, and as a result, the high price.
However, it is possible to assemble such a device. Saving at least 2 times.
We offer an option for “advanced” nickel-cadmium batteries equipped with a third signal contact.
The circuit is assembled on the popular MAX713 controller. Steps to take when replacing the power supply for a 12V and 18V screwdriver with your own hands. You can find a suitable power source in the market or from someone you know. The proposed implementation is designed for an input voltage of 25 volts DC. It is not difficult to assemble such a power supply, so we omit its circuit diagram.
The charger is intelligent. After checking the voltage level, the accelerated discharge mode starts (to prevent the memory effect). Charging occurs in 1-1.15 hours. A special feature of the circuit is the ability to select the charging voltage and battery type. The description in the figure indicates the position of the jumpers and the value of resistor R19 for changing modes.
If branded charger If a professional screwdriver fails, you can save on repairs by assembling the circuit yourself.
power unit for a screwdriver - diagram and assembly procedure
Many people are familiar with the situation: the screwdriver is alive and well, but the battery pack has died. There are many ways to restore a battery, but not everyone likes to tinker with toxic elements.
How to use an electrical appliance
The answer is simple: connect an external power supply. If you have a typical Chinese device with 14.4 volt batteries, you can use a car battery (convenient for working in the garage). Or you can choose a transformer with an output of 15-17 volts and assemble a full-fledged power supply.
The set of parts is the most inexpensive. Rectifier (diode bridge) and thermostat to protect against overheating. The remaining elements have a service task - indicating input and output voltage. No stabilizer required - your screwdriver's electric motor is not as demanding as the battery.
If your screwdriver batteries are completely out of order, then you can convert it to a mains one, how to make one in this video
Here you can download the printed circuit board in lay format
This is what the charger conversion circuit looks like. 
