Homemade battery for a screwdriver. How to convert a screwdriver battery to lithium-ion: step-by-step instructions

Most outdated models cordless screwdrivers was equipped with NiCd batteries. As everyone knows, these batteries are not allocated high power, moreover, they have a “memory” effect, due to which the capacity volume is significantly reduced. Therefore, many owners of such equipment take up the task of converting screwdrivers to lithium batteries 12B 18650. The process is labor-intensive, but if you follow the steps, the result will be crowned with success.

Pros and cons of modernization

Before converting a screwdriver to 18650 lithium batteries, you need to understand what the master will get as a result. The advantages of these manipulations are as follows:

• multiple increase in screwdriver operating time;
• increasing the speed of battery charging - for a full supply of energy for lithium batteries, approximately 1 hour is needed;
• increasing the charging current power to 1-2 C;
• reducing the cost of regularly purchasing new ones NiCd batteries due to their insufficient service life;
• The complete absence of memory effect in lithium batteries.

Also, before converting the battery with your own hands to a more modern technology, you should be aware of the negative consequences:

• it is necessary to connect a controller to determine the charge level, since the device cannot be charged more than 4.2 V and discharged less than 2.7 V;
• lithium-ion batteries for screwdrivers of the Li-lon series lose their capabilities when used in low temperature conditions;
• when converting a screwdriver to lithium battery It may be difficult to adapt a memory from NiCd; here you will have to use a universal device.

Preparatory moments

First of all, you should determine the maximum voltage value. For this purpose, it is necessary to calculate the number of elements. For three parts, the most acceptable value is 12 Volts, for 4 parts - 16 V.

Take a screwdriver battery with a maximum voltage of 14.4 V as a basis. In this case, it is recommended to use 4 cells. This will not only equalize the difference in volts, but also increase the capacitance. It turns out that lithium battery-powered screwdrivers can work much longer.

As for the type of batteries, experts recommend giving preference to the 18650 series; it is the most optimal option. Next you need to figure out the capacity and discharge current. During normal operation of the device, the current consumption level varies within 5-10 Am. But if an unexpected sharp descent occurs, the value rises to 25 Am. In order not to harm the battery during such a drop, it is recommended to select elements with increased value discharge current, for example, up to 30 Am.

Instead of four lithium ion cans, eight can be used. But for this you need to fasten 2 elements in parallel. Next, the connecting pairs must be connected in series. It is important to consider here that not all battery cases can accommodate 8 parts at the same time.

The controller must be selected according to the rated voltage, as well as taking into account the discharge current. These values ​​must match. More precisely, the voltage will be completely the same for both the battery and the controller, but only the operating discharge current must be 2 times less than the limit.

Using an example, it looks like this - the charging-discharging control device is designed for 13-14 Am, while the protective function will turn on when the current sharply increases to 30 Am.

Even when converting a screwdriver to lithium, it is necessary to take into account the dimensions of the protective board, since it must completely fit into the equipment body. Otherwise, you need to use your imagination to increase the body part. It is strictly not recommended to leave this part open.

Step-by-step instruction

Once all the components and tools for replacing the batteries in the screwdriver are prepared, you can begin assembly. As an example, the conversion of 12 volt equipment to a Li-lon battery was dismantled, inside which there were 12 NiCd battery cans of 1.2 V each.

1. First of all, you need to dismantle the case and remove the built-in battery from it. This requires wire cutters because the connector itself must remain in place.
2. Take the controller device and thermocouple. These elements must be installed in the area where the temperature sensor was. By the way, if this part has not yet been removed, it should be removed. You also need to remember that you need to select all the parts so that they can fit into the tool body.

1. After this, solder all prepared parts in strict sequence. Solder the controller to the board according to the selected circuit. The main thing here is not to forget to connect the balancing points. For this purpose, the diagram has a special connector and wiring.
2. The final stage is connecting the output to the pole and minus.
3. The main part of the work is done, now all that remains is to carefully assemble everything into the case without damaging anything.

If the kit included a standard charger, then there will be no problems with them. Such devices are quite suitable for lithium battery packs. All the charge will also be supplied through the controller, which completely eliminates the possibility of battery overheating from power surges.

Many people wonder if it is possible to make a charger that will charge two types of batteries? Circuits for such devices exist, and they work, but using such a charger is not recommended due to the difference in voltage between the battery packs.

New battery packs on the market sell for an average of about 2000-3000 rubles. And the cost of upgrading nickel-cadmium to lithium-ion does not exceed 1000 rubles. Therefore, the rework is completely justified.

VIDEO: How to transfer a screwdriver to lithium batteries (welding batteries into a battery)

The cost of a new screwdriver is approximately 70% the cost of its battery. Therefore, it is not surprising when, faced with a battery failure, we ask ourselves the question - what next? Buy new battery or a screwdriver, or maybe there is an opportunity to repair the screwdriver battery with your own hands and continue working with an already familiar tool?

In this article, which we will roughly divide into three parts, we will look at: the types of batteries that are used in screwdrivers (Part 1), their possible reasons failure (part 2) and available methods repair (part 3).

Screwdriver battery: design and types

It should be noted that regardless of the brand of screwdriver and the country of manufacture, the batteries have an identical structure. The assembled battery pack looks like this.

If we take it apart, we will see that it is assembled from small elements that are assembled sequentially. And from the school physics course we know that elements that are connected in series balance their potentials.

Note. The sum of each battery element gives us the final voltage at the battery contacts.

Set pieces or "cans" usually have standard size and voltage, they differ only in capacitance. Battery capacity is measured in Ah and is indicated on the cell (shown below).

Screwdrivers are used to assemble batteries the following types elements:

• nickel - cadmium (Ni - Cd) batteries, with a nominal voltage on the “banks” of 1.2V;
• nickel-metal hydride (Ni-MH), element voltage - 1.2V;
• lithium-ion (Li-Ion), with a voltage of 3.6V.

Let's take a closer look at the advantages and disadvantages of each type.

• The most common type due to its low cost;
• Low temperatures are not scary, for example, like Li-Ion batteries;
• It is stored in a discharged state, while retaining its characteristics.

• Produced only in third world countries due to toxicity during production;
• Memory effect;
• Self-discharge;
• Small capacity;
• A small number of charge/discharge cycles means they do not “live” for a long time with intensive use.

• Environmentally friendly production, it is possible to purchase a high-quality branded battery;
• Low memory effect;
• Low self-discharge;
• Large capacity compared to Ni - Cd;
• More charge/discharge cycles.

• Price;
• Loses some of its characteristics when stored for a long time in a discharged state;
• At low temperatures Oh, he doesn’t “live” for long.

• No memory effect;
• Almost no self-discharge;
• High battery capacity;
• The number of charge/discharge cycles is many times greater than that of previous types of batteries;
• To set the required voltage, a smaller number of “cans” are needed, which significantly reduces the weight and dimensions of the battery.

• High price, almost 3 times compared to nickel-cadmium;
• After three years, a significant loss of capacity occurs, because Li decomposes.

We got acquainted with the elements, let's move on to the remaining elements of the screwdriver battery pack. Disassembling the unit, for example, to repair the battery of a Hitachi screwdriver (shown below), is very simple - unscrew the screws around the perimeter and disconnect the case.

The housing has four contacts:

• Two power ones, “+” and “-”, for charge/discharge;
• The upper control is switched on via a temperature sensor (thermistor). The thermistor is necessary to protect the batteries; it turns off or limits the charging current when a certain temperature of the elements is exceeded (usually in the range of 50 - 600C). Heating occurs due to high currents during forced charging, the so-called “fast” charging;
• The so-called “service” contact, which is connected through a 9Kohm resistance. It is used for complex charging stations, which equalize the charge on all battery cells. In everyday life, such stations are useless due to their high cost.

That's the whole design of the battery. Below is a video on how to disassemble the block.

Troubleshooting

We have figured out the purpose of the battery design elements, now let’s look at how to determine the malfunction, this is part 2 of repairing a screwdriver battery. Let us immediately note that all elements cannot fail at once, and since our circuit is sequential, if one element fails, the entire circuit does not work. This means that our task is to determine where the weakest link is in our chain.

​

To do this, we will need a multimeter, and for the second method of troubleshooting, a 12V lamp, if your battery for the screwdriver is also 12 volt. The procedure is as follows:

We put the battery on charge and wait for a signal about full charge.

We disassemble the case and measure on each battery bank. For Ni - Cd we should have 1.2 - 1.4V, for lithium - 3.6/3.8V.

Mark all “banks” in which the voltage is less than the nominal one. For example, most Ni-Cd elements have a voltage of 1.3V, and one or more have a voltage of 1.2/1.1V.

We assemble the battery and work until there is a noticeable loss of power.

We remove, disassemble and measure the voltage drop on the battery “banks”. On the marked elements the voltage “sag” will be greater than on others. For example, they are no longer 1.2V, but 1.0V or even lower.

Note. A difference between the elements in a battery of 0.5 - 0.7V is considered significant, which means that the element becomes unusable.

Thus, we found candidates for “reanimation” or “amputation” and replacement with new elements.

If your screwdriver operates on a voltage of 12 or 13V, you can search using a simpler method. We disassemble a fully charged battery and connect a 12 volt lamp to the “+” and “-” contacts. The lamp will be a load and will drain the battery. Next, we take measurements on the battery elements, where the voltage drop is greatest, there is a weak link.

There are other ways, instead of a lamp you can select a resistance, but this already requires the basics of electrical engineering, and it is doubtful that a resistor with the necessary resistance would be at hand.

Other malfunctions are very rare. For example, loss of contact in the soldering areas of batteries or power contacts of the unit, failure of the thermistor. This problem is more common with fakes. Due to its rarity, we will not focus on the battery elements.

The “problematic” elements have been dealt with and need to be repaired. How to repair a screwdriver battery? In general, there are 2 methods available for repair, so to speak. This is the restoration and replacement of elements that have become unusable.

Is it possible to “reanimate” elements and how?

Let's proceed to part 3 of screwdriver battery repair and immediately make a reservation that the concept of “reanimation” for lithium is ion batteries not applicable. There is no memory effect in them; most likely, lithium decomposition has occurred, and nothing can be done about it. In such batteries, it is necessary to find out what is the cause of the malfunction: the element itself or the control circuit. There are two options here:

• we change the control circuit from another, but similar to ours, battery, if it helps, we find a replacement and change it;
• apply 4V to an element with a current of approximately 200mA, for this you need an adjustable Charger. If the voltage on the element increases to 3.6V, the element is working properly, the problem is in other elements, or in the control circuit.

Screwdriver battery repair is available primarily for Ni-Cd batteries, but they are usually the most common in household screwdrivers.

So, how to reanimate a screwdriver battery? There are two types of “reanimation” for these types of batteries:

1. Compaction or compression method (this will work in cases where the electrolyte is still available, but volume has been lost);
2. “Firmware” with voltage and current greater than the nominal one. This method allows you to eliminate the memory effect, and although not completely, restore the lost capacity.

This method is shown in the video below.

Note. As a rule, in a nickel-cadmium battery the main reason for loss of capacity is boiling away of the electrolyte, and if it is critically low, no amount of “firmware” will help.

This method, if its result is positive, will not solve the problem of element failure. Rather, it will only delay the replacement of those that have become unusable, and in the future you will still need to repair the battery of a Makita screwdriver or any other.

Repair and replacement of screwdriver battery elements

A more effective way to repair batteries for a screwdriver is to replace the elements that we have identified as faulty.

To carry out repairs, we need either a “donor” battery, in which some of the elements are working, or new “banks”. Purchasing them will not be difficult; even on the Internet you can easily find a dozen stores that are ready to send these items by mail. The price is not particularly bad, for example, a nickel-cadmium cell with a capacity of 2000 mAh costs around 100 rubles.

Note. When purchasing a new element, make sure that its capacity and dimensions match the original elements.

We will also need a soldering iron, low-corrosive flux (preferably alcohol flux with rosin) and tin. We are not talking about spot welding, since for a one-time battery repair there is hardly a need to purchase or assemble it...

There is nothing complicated about the replacement itself, especially if you have at least some experience in soldering. The photographs show everything in sufficient detail; we cut off the faulty element and solder a new one in its place.

Several points need to be noted:

• When soldering with a soldering iron, try to solder quickly so that the battery does not heat up, because you risk ruining it;
• if possible, make the connection using original plates, or use copper plates of the same size, this is important because the charging currents are large and if the connecting wires are of the wrong cross-section, they will heat up, and accordingly the thermistor protection will be triggered;
• Do not under any circumstances confuse the plus of the battery with the minus - the connection is in series, which means that the minus of the previous can goes to the plus of the new can, and the minus of the new one goes to the plus of the next one.

After the new elements have been soldered, it is necessary to equalize the potentials on the “banks”, since they are different. We carry out a charge/discharge cycle: set it to charge overnight, give it a day to cool down and measure the voltage on the elements. If we did everything correctly, the picture will be something like this: all elements have the same multimeter reading, within 1.3V.

Next, we proceed to discharge the battery, insert the battery into the screwdriver and load it “to its fullest.” The main thing is to spare the screwdriver itself, otherwise you will have to repair it too. We bring it to full discharge. We repeat this procedure two more times, i.e. charge and completely discharge.

It should be noted that the procedure for erasing the “memory effect” should be carried out every three months. It is carried out in a similar way to the training described above.

This not-so-tricky procedure will prolong the operation of your screwdriver, at least until it has to be replaced with a new one.

In this article you will learn how to inexpensively convert a screwdriver battery from Ni Cd to Li Ion 18650 batteries, thereby modernizing screwdriver battery, making it more powerful and increasing battery life. All stages of the conversion are described in detail, so there should be no problems, all the necessary components are indicated and available.

Required components for conversion

For rewhitening, high-current 18650 batteries capacity 2500 mAh. Data batteries They have already welded leads for soldering, which is very convenient and, in addition, you can significantly save on battery compartments. You can order them online and are supplied in batches of 4 or 6 pieces. You can buy them using the links below:

Buy 18650 batteries - 6 pcs.

Buy 18650 batteries - 4 pcs.

Also for the conversion you will need two BMS 12.6V 40A boards, bought here:

Buy BMS board 12.6V 40A

The charger will also need to be redone and for this you will need a voltage and current stabilization module.

For a video on how to remake a charger, see the end of the article.

Buy voltage and current stabilization

At the time of the conversion, all components (for two batteries) cost only 1,100 rubles, this is much cheaper than buying a new battery for a screwdriver, which will contain the same Ni Cd batteries. After looking at prices on the Internet, I discovered that one battery costs from 1200 rubles, and to remake TWO batteries, I spent only 1100! All links to components can also be found at the end of the article!

Battery conversion

The first step is to carefully disassemble the battery case and throw away the old Ni Cd batteries.

Then you need to disconnect the battery power terminal.

You need to solder two wires to it, preferably with a large cross-section; in this modification, wires with a cross-section of 4 mm² and a length of approximately 100 mm were used. In the photo above you can see the red wire, it was left in order not to confuse the polarity; it is advisable to also solder the red wire to this wire in order to avoid troubles and you will know for sure that it is +.

The shiny contact needs to be soldered negative wire:

Then you need to insert the terminal with the soldered wires back into the housing in its place, being sure to observe the polarity!

To fix the terminal, you can pour hot glue inside the glass; I haven’t found a better fixing option, especially since it holds very well!

Now you can start soldering the batteries. We remove the heat-shrink tube from the batteries and bend them so that they can be soldered in series.

Next, we apply hot melt glue to the side of the resulting battery, where the contacts stick out to the top, and glue the BMS board as shown in the photo below. Please note that the plus and minus of the board and battery are opposite each other!!!

Then we bend the battery contacts onto the board contacts and solder them, starting from the negative!

We solder a short wire to the contact of the B1 board, the other end of which we solder to the junction of the batteries!

We also solder a short wire to contact B2, the other end of which is soldered to the junction of the batteries on the opposite side!

Well, at the end, we solder the last, positive contact.

Now it remains to connect the terminals of the case with the resulting battery; to do this, solder the red wire to the “P+” contact, and the blue, negative wire to the “P-” contact.

This completes the battery conversion! All that remains is to secure the manufactured battery and put the second part of the case in place. No more than an hour of time and, as mentioned above, 1,100 rubles of money were spent on converting two batteries. After the tests, the screwdriver began to work no worse than with the factory battery and, I would say, much better in terms of power and the charge lasts longer. I advise everyone to remake their old batteries!))
Buy charger socket
Buy a soldering iron

For those who have no desire to remake the charger, you can buy a ready-made one using the link below.

Buy a ready-made charger

The industry has been making screwdrivers for a long time, and many people have older models with nickel-cadmium and nickel-metal hydride batteries. Converting a screwdriver to lithium will improve performance characteristics device without buying a new tool. Now many companies offer services for converting screwdriver batteries, but you can do it yourself.

Benefits of lithium-ion batteries

Nickel-cadmium batteries have a low price, withstand many charging cycles, and are not afraid of low temperatures. But the battery capacity will decrease if you charge it before it is completely discharged (memory effect).

Lithium-ion batteries have the following advantages:

• high capacity, which will ensure longer operating time of the screwdriver;
• smaller size and weight;
• retains charge well when not in use.

But a lithium battery for a screwdriver does not withstand full discharge well, so factory tools on such batteries are equipped with additional circuit boards that protect the battery from overheating, short circuit, and overcharging to avoid explosion or complete discharge. When the microcircuit is installed directly into the battery, the circuit opens if the unused battery is located separately from the tool.

Difficulties in reworking

IN Li-Ion batteries There are objective disadvantages, such as poor performance at low temperatures. In addition, when converting a screwdriver to 18650 lithium batteries, you may encounter a number of difficulties:

1. The 18650 standard means that the diameter of one battery cell is 18 mm with a length of 65 mm. These dimensions do not coincide with the dimensions of the nickel-cadmium or nickel-metal hydride elements previously installed in the screwdriver. Replacing batteries will require placing them in a standard battery case, plus installing a protective microcircuit and connecting wires;
2. The output voltage of lithium cells is 3.6 V, and for nickel-cadmium cells it is 1.2 V. Let’s say the nominal voltage of the old battery is 12 V. This is the voltage when connected in series Li-Ion cells cannot be provided. Voltage fluctuations during charge-discharge cycles ion battery also change. Accordingly, converted batteries may not be compatible with the screwdriver;
3. Ion batteries differ in the specifics of their operation. They do not withstand overcharge voltages greater than 4.2 V and discharge voltages less than 2.7 V until they fail. Therefore, when the battery is rebuilt, a protective board must be installed in the screwdriver;
4. The existing charger may not be able to be used for a screwdriver with a Li-Ion battery. You will also need to remake it or purchase another one.

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

Battery selection

Screwdrivers often use 12 V batteries. Factors to consider when choosing Li-Ion battery for a screwdriver:

1. Such instruments use elements with high discharge current values;
2. In many cases, the capacity of the element is inversely related to the discharge current, so you cannot select it based on capacity alone. The main indicator is current. The value of the operating current of the screwdriver can be found in the tool passport. Usually it is from 15 to 30-40 A;
3. When replacing a screwdriver battery with a Li-Ion 18650, it is not recommended to use cells with different capacity values;
4. Sometimes there are tips to use a lithium battery from an old laptop. This is absolutely unacceptable. They are designed for a much lower discharge current and have unsuitable technical characteristics;
5. The number of elements is calculated based on the approximate ratio - 1 Li-Ion to 3 Ni-Cd. For a 12-volt battery, you will need to replace 10 old cans with 3 new ones. The voltage level will be slightly reduced, but if you install 4 elements, then increased voltage will shorten the life of the electric motor.

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

Disassembling the battery case

The case is often assembled using self-tapping screws, other options are assembled using latches or glue. The glued block is the most difficult to disassemble; you have to use a special hammer with a plastic head so as not to damage parts of the body. Everything from inside is removed. You can reuse only the contact plates or the entire terminal assembly for connecting to a tool or charger.

Battery Cell Connection

CompoundLi– Ionbatteries for screwdriverperformed in several ways:

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

Important! The elements must be connected in series, then the battery voltage is added, but the capacity does not change.

At the second stage, the wires are soldered to the contacts of the assembled battery and to the protective board according to the connection diagram. Wires with a cross-sectional area of ​​1.5 mm² are soldered to the contacts of the battery itself for power circuits. For other circuits, you can take thinner wires - 0.75 mm²;

A piece of heat shrink tubing is then placed over the battery, but this is not necessary. You can also put heat shrink on the protective microcircuit to isolate it from contact with the batteries, otherwise sharp solder protrusions can damage the shell of the element and cause a short circuit.

Further battery replacement consists of the following steps:

1. The disassembled parts of the body are well cleaned;
2. Since the dimensions of the new battery cells will be smaller, they need to be securely fixed: glued to the inner wall of the case with Moment glue or sealant;
3. The positive and negative wires are soldered to the old terminal block, it is placed in its original place in the housing and fixed. The protective board is laid, the parts of the battery pack are connected. If they were previously glued, then “Moment” is used again.

The lithium-ion battery of the screwdriver will not be able to function properly without the BMS protection board. The copies sold have different parameters. The BMS 3S marking assumes, for example, that the board is designed for 3 elements.

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

1. The presence of balancing to ensure uniform charge of the elements. If it is present, the description of the technical data should include the value of the balancing current;
2. The maximum value of operating current that can be withstood for a long time. On average, you need to focus on 20-30 A. But this depends on the power of the screwdriver. Low-power ones need 20 A, high-power ones – from 30 A;
3. Voltage at which the batteries are switched off when overcharging (about 4.3 V);
4. The voltage at which the screwdriver turns off. This value must be selected based on technical parameters battery cell ( minimum voltage- about 2.6 V);
5. Overload protection current;
6. Resistance of transistor elements (select the minimum value).

Important! The magnitude of the operating current during overload does not have of great importance. This value is adjusted to the operating load current. In case of short-term overloads, even if the tool has turned off, you must release the start button, and then you can continue to work.

Whether the controller has an autostart function can be determined by the presence of the “Automatic recovery” entry in the technical data. If there is no such function, then in order to start the screwdriver again after the protection has tripped, you will need to remove the battery and connect it to the charger.

Charger

The lithium-ion battery of the screwdriver cannot be charged by connecting it to a conventional power supply. A charger is used for this. The power supply simply produces a stable charge voltage within specified limits. And in the charger, the determining parameter is the charge current, which affects the voltage level. Its meaning is limited. The charger circuit contains nodes responsible for stopping the charging process and other protective functions, for example, shutdown in case of incorrect polarity.

The simplest memory is a power supply with a resistance included in the circuit to reduce charging current. Sometimes they also connect a timer that fires after a set time period has passed. All of these options are not conducive to long battery life.

Charging methodsLI Ionbatteries for screwdriver:

1. Using a factory charger. Often it is also suitable for charging a new battery;
2. Redesign of the charger circuit, with installation additional elements scheme;
3. Purchase of a ready-made memory. A good option– IMax.

Let's say there is an old Makita DC9710 charger for charging Ni-Cd 12 V batteries, with indication in the form of a green LED signaling the end of the process. The presence of a BMS board will allow you to stop the charge when the specified voltage limits per element are reached. The green LED will not light up, but the red one will simply go out. The charge is complete.

The Makita DC1414 T charger is designed to charge a wide range of batteries 7.2-14.4 V. In it, when the protective shutdown is triggered at the end of the charge, the indication will not work correctly. The red and green lights flash, which also signals the end of the charge.

The cost of replacing screwdriver batteries with lithium-ion ones depends on the power of the tool, the need to buy a charger, etc. But if the drill/driver is in good functional condition and the charger does not require major alteration or replacement, then for a couple of thousand rubles you can get an improved power tool with increased battery life.

Video

In the arsenal of any good owner there will probably be a power tool that is common in everyday life - a screwdriver. Its main advantage is mobility. After all, this device runs on removable batteries, which makes its use as convenient as possible, since it does not require connecting to a power outlet. But what if the battery of the screwdriver fails? Buying a new one will be quite expensive, because its cost in some models reaches 50–70% of the price of the screwdriver itself. It will be much more practical to immediately purchase a new tool, which includes two batteries. But you can still extend the service life of an old screwdriver by repairing a failed battery.

What is a screwdriver battery?

In any model of electric screwdriver, such an important element as the battery looks approximately the same. It is a plastic box containing up to a dozen (and sometimes more) batteries. They are connected to each other in a serial chain and are arranged in such a way that the terminals of the first and last jar in the chain are closed to contacts that provide power to the tool and connection to the charger.

The batteries of any type of screwdriver have a fairly simple design, which can be easily understood by anyone with at least a little knowledge of the basics of electrical engineering. In addition to batteries, the battery housing may contain:

Depending on the type of batteries used, screwdriver batteries are of the following types:

• nickel-cadmium, designated NiCd and designed for a nominal voltage of 12 V;
• nickel metal hydride (NiMh) with the same rated voltage as the first type (12 V);
• lithium-ion (Li-Ion), the voltage of which, depending on the number of elements used, can range from 14.4 to 36 V.

Rechargeable batteries of the first type (NiCd) are the most common in modern tools, primarily due to their lowest cost. Batteries based on nickel-cadmium alloy can be found especially often in budget models screwdrivers. They are not afraid of low temperatures and can be stored in a discharged state without losing their characteristics. The disadvantages of such batteries include:

• a pronounced memory effect, when, when the charge is not fully developed, the battery seems to remember to what value its capacity was used, and in the future it is no longer charged above these parameters;
• small capacity and small number of charge and discharge cycles;
• susceptibility to self-discharge, when an unused charged battery gradually loses its charge;
• high toxicity when opening the can due to the cadmium contained in the battery.

To ensure that a new battery for a screwdriver does not lose capacity, it must be charged for 10–12 hours the first few times, even if an indication appears that it was charged much earlier. During operation, it is better to use the battery until it is completely discharged, and then immediately connect it to the charger until it is fully charged.

Nickel-metal hydride elements are also common in modern screwdrivers. They consist of environmentally friendly elements, but are more expensive than nickel-cadmium batteries. They have lower self-discharge and memory effect and a higher number of charge cycles than NiCd cells. But they are afraid of low temperatures and, when discharged, also lose their characteristics.

The most expensive are lithium-ion batteries, which, compared to the first two types, have noticeable advantages:

Among the disadvantages of batteries of this type, their short service life should be noted. After three years, lithium begins to decompose and the battery loses its capacity beyond recovery.

Typical screwdriver battery malfunctions

Despite the fact that the screwdrivers are equipped different types batteries, they all have the same design and similar faults. The most common failures of this device are:

• loss of capacity of one or more batteries;
• mechanical damage to the battery pack circuit (separation of the plates connecting the banks to each other or to the terminals);
• drying out of the electrolyte;
• Lithium decomposition in Li-Ion cells.

Loss of battery capacity is the most common defect in screwdriver batteries. Its essence is that the loss of the charge capacity of at least one battery does not make it possible to fully charge the remaining banks. When receiving a low-quality charge, the battery quickly discharges.

Such a malfunction may be a consequence of the memory effect or drying out of the electrolyte in the banks due to their heating during charging or under load. This defect in batteries of any type can be eliminated independently, without contacting service center. In this case, you can try to restore faulty elements or replace them. It will not be possible to restore only lithium-ion batteries that have lost capacity as a result of lithium decomposition. Such banks can only be replaced with new ones removed from a non-functioning battery pack.

DIY screwdriver battery repair

Most defects in the battery pack of a screwdriver can be eliminated yourself if you know the cause of the malfunction and how to deal with it.

Diagnostics of screwdriver battery faults

Before you begin repairing the battery, you need to diagnose it and identify the cause of the malfunction. To do this you need:

1. Fully charge the battery pack. A nickel-cadmium or nickel-metal hydride battery must first be discharged to zero to avoid memory effect.
2. Disassemble the battery case by removing its cover. It can be fastened with screws or glued, which will make disassembly somewhat difficult. In the second case, to remove the cover, you need to use a sharp scalpel or knife to walk along the adhesive joint, and then, carefully prying it off with a thin screwdriver, disconnect the cover.

   The battery pack cover can be attached to the battery housing with screws or glue

3. By visual inspection, determine the presence of mechanical damage, broken circuits, as well as swollen or leaking battery cans.

   After disassembling the battery pack, perform a visual inspection of the contents for obvious defects.

4. Measure the voltage on each battery with a multimeter. For batteries such as NiCd or NiMh, it should be in the range of 1.2–1.4 V, and for lithium-ion banks - 3.6–3.8 V. It is better to write the measured value on each bank with a pencil to avoid confusion.

   By measuring the voltage on each bank, you can find all the faulty elements

5. Load the battery by connecting a regular car light bulb or resistor to the output contacts.

   By connecting the lamp, we let the batteries work to show the voltage drop under load.

6. After holding the battery under load, measure the voltage on each bank again and find the batteries where the maximum drawdown occurred. These are the defective elements.

Video: how to completely discharge a screwdriver battery

Having found faulty batteries, you need to decide on how to repair them. There are two possible options here. The first is to revive defective batteries by flashing them with a current with more high voltage or add distilled water to the jars if the electrolyte dries out. But these measures are temporary; in the future, the malfunction may appear again. Another repair method that is more effective is to replace defective batteries with new or used ones that are known to be good.

Video: searching for defective batteries in a screwdriver battery

Battery recovery

Restoring the lost capacity of a battery is possible only for batteries with a memory effect. These are nickel-cadmium and nickel-metal hydride batteries. To do this, you will need a more powerful charger with adjustable voltage and current settings. Having set the voltage to about 4 V and the current to 200 mA, we apply this current to the batteries in which the maximum voltage drop is detected.

You can try to restore defective batteries by compressing or compacting them. This procedure is a dilution of the electrolyte, the volume of which in the battery bank has decreased. To do this you need:

The procedure described in paragraph 5 can, under certain conditions, restore the functionality of the battery if the cause of its malfunction is the memory effect.

Video: the process of restoring the capacity of screwdriver batteries

Replacing batteries

The most effective way to repair a screwdriver battery is to replace the defective can. To do this, you can use a new battery, which can easily be found on sale today, or remove a working jar from a non-functioning battery pack. Replacement work must be carried out in the following sequence:

1. Remove the faulty battery from the battery circuit. Considering that they are all connected to each other by plates mounted on spot welding, it is best to use side cutters for this purpose. In this case, you need to leave a sufficiently long shank on a working can in order to be able to solder it to a new battery.

   On working cans, you need to leave the shanks so that they can be soldered; on a faulty can, this is not necessary

2. Solder the new battery in place of the removed defective can, observing the required polarity. The positive terminal is soldered to the negative terminal of the “neighbor”, and the negative terminal is soldered, respectively, to the positive terminal. To do this, you will need a soldering iron with a power of at least 40 W and soldering acid. If it was not possible to maintain a sufficient length of the plate, you can connect the cans with a copper conductor.

   For soldering, use a soldering iron with a power of at least 40 W and soldering acid.

3. Assemble the batteries into the case according to the same pattern in which they were placed before repair.

   After installing a working can, the entire chain must be put back into the battery box

4. Equalize the charge on each bank by repeating the charge-discharge cycle several times. Then check the voltage potentials on each bank with a multimeter. They should be at the same level - 1.3 V.

It is important not to overheat the can when performing soldering work. Therefore, you cannot hold the soldering iron tip on the battery for too long.

Repair of battery packs with lithium-ion type banks is carried out in the same way. The only thing that complicates the repair task is disconnecting the batteries from the control board. In this case, only one repair method is applicable - replacing the defective can.

Video: how to properly solder screwdriver battery banks

How to convert a screwdriver battery to lithium-ion batteries

Often, owners of screwdrivers with nickel-cadmium batteries want to convert their batteries to lithium-ion batteries. They are attracted by the advantages that can be acquired by such a modification of the battery pack:

• Lighten the weight of the screwdriver, the operation of which will require fewer batteries at the same battery capacity and voltage;
• get rid of the memory effect, which is not present in lithium-ion batteries;
• reduce battery charging time.

In addition, with a certain assembly scheme, you can double the charge capacity, and therefore the operating time of the screwdriver on a single charge. The advantages, of course, are obvious, but this solution also has its disadvantages, which you also need to know in order to weigh the pros and cons. Among the negative aspects of adapting a screwdriver battery to lithium-ion banks, the following should be noted:

• higher cost of lithium-ion batteries;
• the need to maintain the charge level of the element strictly within the range from 2.7 to 4.2 V, for which it will be necessary to additionally install a charge-discharge controller board in the battery box;
• large sizes of Li-Ion batteries, which will require ingenuity and imagination to place them in the screwdriver battery case;
• it is impossible to use the tool with such batteries in low temperatures.

But if the decision to replace nickel-cadmium batteries is still made, then you need to proceed in the following sequence:

1. Decide on the number of lithium-ion batteries and their electrical characteristics. For example, for the most common screwdriver powered by a battery with a nominal voltage of 14.4 V, it is better to take 4 lithium-ion cells, the total maximum voltage of which will be equal to 4.2 x 4 = 16.8 V. Here it is necessary to take into account that immediately after starting work on new batteries the voltage across them will drop and will be equal to 14.4–14.8 V. If the capacity of the battery pack box allows, you can take 8 of these cans, forming 4 pairs of them with batteries connected in parallel. This will increase the battery capacity by 2 times.
2. Select a controller board for 4 batteries. Its parameters must correspond to the discharge current and rated voltage of the selected batteries. In this case, the operating discharge current should be 2 times less than the maximum permissible value battery discharge current, which is usually 25–30 A. This means that the board must be designed for a current of 12–15 A.

   The controller board must be designed to work with the required number of batteries and be designed for their operating discharge current

3. Disassemble the screwdriver battery box and remove all nickel-cadmium cans from it. Cut the entire chain with wire cutters or side cutters, leaving only the top element with contacts for connecting to the tool. The thermistor can also be removed, since overheating of the batteries will now be monitored by the controller board.

   When connecting the control controller board to a chain of lithium-ion batteries, the polarity must be observed. Lithium-ion batteries are best placed horizontally in the screwdriver battery case

4. Close the battery with a lid, installing a battery with contacts on an old type battery on the batteries laid horizontally.

It may turn out that the assembled structure cannot be charged from the old charger. Then you need to install an additional connector for a new charge.

Video: replacing nickel-cadmium batteries with lithium-ion ones

How to properly store screwdriver batteries

In order for the screwdriver battery to last as long as possible, it must be stored correctly, especially when it is not used very often and with long breaks. In this case, you need to follow some rules.

Cadmium-based battery packs have a memory effect, which reduces the battery capacity when the charge is incomplete. Therefore, batteries with NiCd and NiMh batteries should be stored in a discharged state, and devices with lithium-ion batteries should be charged to half the capacity of the cans. This level can be achieved in approximately 65–70% of the normal full charge time.

If the battery pack of your screwdriver begins to discharge quickly and does not hold a charge at all, do not rush to throw it away and buy a new one. Its service life can be easily extended using the recommendations outlined above. This will save you from unnecessary costs, because the battery of a screwdriver costs more than half the cost of the entire tool.