In the arsenal of any good host, there will certainly be a power tool, widely used today in everyday life - a screwdriver. Its main advantage is mobility. After all, this device works on removable batteries, which makes its use as convenient as it does not need to be connected to an electrical outlet. But what if the battery (battery) of the screwdriver is out of order? 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 instrument, which includes two batteries. But you can still extend the life of an old screwdriver by repairing the failed battery.

What is a screwdriver battery?

In any models of electroshockers, an important element, like a battery, looks approximately the same. It is a plastic box, inside which are placed up to a dozen (and sometimes more) batteries. They are connected to each other in a sequential chain and arranged in such a way that the conclusions of the first and The last jar in the circuit closes to the contacts providing power to the instrument and connection to the charging device.

AKB screwdrivers of any type have a fairly simple design, which can easily understand any person who is a little familiar with the basics of electrical engineering. In addition to the batteries, the battery housing may contain:

• thermistor (thermal sensor) to protect the battery cells from overheating during charging and a thermal breaker serving to open the charge circuit when it overheats;
• Controller board (only lithium-ion battery).

  Lithium-ion batteries are operated by a special controller

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

• nickel-cadmium, denoted by the symbols NiCd and rated for a nominal voltage of 12 V;
• nickel-metal hydride (NiMh) with the same nominal voltage as the elements of the first type (12 V);
• Lithiumion (Li-Ion), the voltage of which, depending on the number of elements used, can be from 1 to 36 V.

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

• a pronounced memory effect when, as the battery is not fully charged, the battery seems to remember, to what extent its capacitance was used, and in the future it does not charge above these parameters;
• small capacity and a small number of charge and discharge cycles;
• susceptibility to self-discharge, when an unused charged battery gradually loses its charge;
• high toxicity at the opening of the jar due to the cadmium contained in the battery.

To ensure that the new battery for the screw driver does not lose the capacity, the first few times it is needed subject to charging for 10-12 hours, even if an indication appears that it has charged a lot before. In the process of working the battery is better to use until the full discharge, and then immediately connect to the charger until it reaches full charge.

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

The most expensive are lithium-ion batteries, which, in comparison with the first two types, have noticeable advantages:

• do not have a memory effect;
• almost not subject to self-discharge;
• are designed for a greater number of charge cycles and provide a higher capacity;
• They are compact in size, since a smaller number of batteries (cans) are required to dial the desired battery voltage.

  Each cell of a lithium-ion battery has a higher rated voltage, so they are used less than other types of battery

Of the disadvantages of batteries of this type, it should be noted their short life. Three years later lithium begins to decompose, the battery loses its capacity without the possibility of recovery.

Characteristic faults of the screwdriver battery

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

• loss of capacity of one or more batteries;
• mechanical damage to the circuit of the battery pack (detachment of plates connecting the banks between themselves or with terminals);
• drying of the electrolyte;
• decomposition of lithium in elements of the Li-Ion type.

The loss of battery capacity is the most common defect in a screwdriver battery. The essence of it is that the loss of the capacity of a charge of at least one battery does not allow you to fully charge the remaining banks. Receiving a substandard charge, the battery is quickly discharged.

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

Repair of the screwdriver battery with your own hands

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

Diagnostics of faults of the battery screwdriver

Before starting to repair 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. Pre-nickel-cadmium or nickel-metal hydride battery should be discharged to zero, in order to avoid the effect of memory effect.
2. Disassemble the battery case by removing its cover. It can be screwed on or glued to the glue, which will somewhat complicate the disassembly. In the second case, to remove the lid, use a sharp scalpel or knife to walk through the glue joint, and then, gently pulling a thin screwdriver, detach the lid.

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

3. Visual inspection to determine the presence of mechanical damage, rupture of the chain, as well as swollen or overgrown cans of the battery.

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

4. Measure the voltage on each of the batteries with the multimeter. For batteries such as NiCd or NiMh, it should be in the range of, B, and for lithium ion cans, B. On each bank, the measured value is better written in pencil in order to avoid confusion.

   Measuring the voltage on each bank, you can find all the faulty items

5. Load the battery by attaching a normal car bulb or resistance to the output contacts.

   By connecting the lamp, letting the batteries work to show the voltage drop under load

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

Video: how to completely discharge the battery screwdriver

Having found out faulty elements of a feed, it is necessary to be defined with a way of their repair. There are two options for action. The first is to reanimate the defective batteries by piercing them with a current of higher voltage or adding distilled water to the banks in case of electrolyte drying. But these measures are temporary, in the future the malfunction may appear again. More effective is another method of repair, which consists in replacing defective batteries with new or second-hand, but certainly serviceable.

Video: search for defective batteries in the battery screwdriver

Restoring battery cells

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

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

1. Make the smallest hole in the defective power element, in which there was boiling electrolyte, in the end surface from the side of the "minus" contact by means of a thin drill or punch.
2. Pump air from the jar with a syringe to 1 cm3.
3. Using a syringe to insert into the battery, -1 cm3 of distilled water.

   In the body of the battery make a small hole through which the air is pumped out and poured about one "cube" of distilled water

4. Seal the battery can with epoxy resin.
5. To equalize the potential, discharge all the banks of the battery by attaching a third-party load, which can be a conventional 12-volt light bulb, after which the battery is fully charged. Repeat charge-discharge cycles 5-6 times.

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

Video: the process of recovering the capacity of the screwdriver batteries

Battery replacement

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

1. Remove the battery from the battery. Given that all of them are connected to each other by plates, set to spot welding, it is best to use the side cutters for this purpose. At the same time, it is necessary to leave a shank on the working bank of sufficient length to be able to solder it to a new power supply.

   On serviceable banks, it is necessary to leave the shanks so that they can be soldered, it is not necessary to do this on a faulty bank

2. The new battery should be soldered to the location of the remote defective canister, observing the necessary polarity. The plus output is soldered to the minus pin of the "neighbor and the negative one to the positive one, respectively. To do this, you need a soldering iron with a power of at least 40 W and a soldering acid. If you can not keep enough length of the plate, you can connect the cans with a copper conductor.

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

3. Collect the batteries in the housing in the same way as they were laid before repair.

   After installing the serviceable can, the entire chain must be re-packed in a battery box

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

It is important not to overheat the jar when performing soldering works.Therefore, it is impossible to detain the soldering tip of the battery for too long on the battery.

Repair of battery packs with lithium-ion banks is similar. The only thing that complicates the task during repair is the disconnection of the batteries from the control board. In this case, we apply only one method of repair - the replacement of a defective can.

Video: how you need to solder banks of AKB screwdrivers

How to remake the battery of a screwdriver for lithium-ion batteries

Often the owners of screwdrivers on nickel-cadmium batteries want to remake their batteries for lithium-ion batteries. They are attracted by the advantages that can be obtained by such a reworking of the battery pack:

• simplify the weight of the screwdriver, which requires less battery for the same battery capacity and voltage;
• to get rid of the effect of memory, which is not present in lithium ion-type cells;
• reduce battery charging time.

In addition, with a certain assembly scheme, you can double the capacity of the charge, and hence the operating time of the screw driver from one charge. Advantages, of course, are obvious, but this solution has its drawbacks, which you also need to know in order to weigh the pros and cons. From the negative moments of adapting the battery for screwdrivers to lithium-ion banks, it should be noted:

• higher cost of lithium ion-type batteries;
• the need to maintain the level of charge of the element is strictly in the range from, to, B, for which it will be necessary to additionally install a charge-discharge controller card in the battery box;
• large sizes of Li-Ion type batteries, which will require smartness and imagination to place them in the battery case of a screwdriver;
• The inability to use a tool with such batteries in low temperature conditions.

But if the decision to replace the nickel-cadmium batteries is still accepted, then proceed further in the following sequence:

1. Determine the number of lithium-ion batteries and their electrical characteristics. For example, for the most common screwdriver, powered by a battery with a rated voltage 1, B, it is better to take 4 lithium ion elements, the total maximum voltage of which will be equal to x4 = 1, AT. Here it is necessary to take into account that immediately after the start of work on new batteries, the voltage will be applied to them and will be equal to 1, -1, V. If the capacity of the battery box allows, you can take 8 of these cans, forming 4 pairs of them with parallel-connected batteries. This will increase the battery capacity by 2 times.
2. Choose the controller board for 4 batteries. Its parameters should correspond to the discharge current and the rated voltage of the selected batteries. At the same time, the working current of the discharge should be 2 times lower than the maximum permissible value of the discharge current of the batteries, which is usually 25-30 A. Hence, the board should be rated for 12-15 amps.

   The controller board should be designed to work with the right number of batteries and is designed for their operating discharge current

3. Disassemble the screwdriver battery box and remove all nickel-cadmium cans from it. Cut the whole chain with wire cutters or side cutters, leaving only the top element with contacts for connection to the tool. The thermistor can also be removed, since the controller card will now follow the battery overheating.

   From the chain of old cans it is necessary to leave only an element with contacts for connection to a screwdriver

4. Assemble the circuit of lithium-ion batteries, soldering them in series, and attach the controller board according to the scheme, observing the polarity.

   When connecting the control card of the controller to a chain of lithium-ion batteries, the polarity

5. Place the assembled structure in the battery box. Batteries lithiumion type is better to lay horizontally.

   Lithiumion batteries are best placed in the battery case of the screwdriver horizontally

6. Close the battery with the lid, inserting the battery with the old battery contacts on the battery horizontally stacked.

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

Video: replacement of nickel-cadmium batteries with lithium ion batteries

How to properly store screwdriver batteries

To ensure that the screwdriver battery lasts as long as possible, it needs to be stored correctly, especially when it is not used very often and with long interruptions. In doing so, you must follow certain rules.

The cadmium-based storage units have a memory effect that reduces the capacity of the batteries when the charge is not fully charged.Therefore, batteries with NiCd and NiMh batteries should be stored in a discharged state, and devices with lithium ion batteries - charging them for half the capacity of the cans. This level can be achieved in a time equal to approximately 65-70% of the normal full-charge time.

If the battery pack of your screwdriver becomes quickly discharged 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 by using the above recommendations. This will save you unnecessary costs, because AKB screw driver costs more than half of the cost of the entire instrument.