How to repair the battery for an electric screwdriver: fault location and repair

How to repair the battery for an electric screwdriver. this is a frequently asked question among home masters, because this device is in the arsenal of almost every owner. The main advantages of the tool, functioning from the battery, consider compactness, the ability to work with it even at height (due to the absence of power supply wires). Nevertheless, the battery of this device can fail, and it is not profitable to buy a new one, because its price sometimes reaches up to 60% of the cost of the tool. Therefore, it is recommended to try to restore the battery. how exactly, we will tell you today.

Despite the variety of models of these tools, the battery of all wrenches has a similar appearance. It is a box made of plastic, which contains many component batteries. They are fastened to each other in a single chain so that the wires of the “cans” on both sides are shorted to the contacts, which provide power to the screwdriver.

All batteries have a primitive construction that even an inexperienced craftsman with little knowledge of electrical engineering can figure out. In addition to the parts of the power in the box of the unit is often located:

  • Thermistor. allows you to control the temperature of the cells during charging;
  • thermal switch. automatically opens parts of the circuit in case of battery overheating;
  • control and monitoring board (only lithium-ion batteries have it).

You’re a rider or repair flooded GTX 760

Hi there. From this post from time to time will go out repairs made by me in the service center where I work (if interested, all links will be in telegram).Generally speaking, received a video card Palit GTX 760 with 2GB of video memory.

Defect from the owner. I got flooded, and then it stopped detecting in the system. Inspecting the video card and yes, there are traces of flooding. There are a lot of signs of flooding.

Alright, I thought, I’ll have to make some trouble to find the right resistors and capacitors. Oh, come on. I disassemble the video card and

And here I am shocked. I’ve never seen anything like this in my practice before. The liquid is even flowing out of the screw that secures the cooling system. Sighing heavily gently disassemble the video card (so as not to get dirty with this substance) and just fell into shock. See for yourself:

Yeah, I certainly did not expect that. Okay, I put a price tag on it and send it to the customer for approval. After a while I get a reply from the client that it needs to be repaired. Eh, I didn’t want to do this, but I guess I have to. I change the rotten parts and run it in my test bench.

And yes, the card was detected and gave me a picture. You can rejoice, but the image seemed to me kind of strange. And yes, when I run any test, I see a greenish tint, which clearly should not be there. I take a screenshot and the picture is normal.

This is the first time I have encountered such a defect, so I decided to take some time to think. And while I’m thinking about it, I’m starting to clean the video card.

Under a stream of hot water wash off all the fluid on the casing of the cooling system (what is this fluid I do not understand, it is very thick, but under a stream of hot water rinsed away on hurray).

And I throw all metal objects into the alcohol for half an hour, stirring them periodically.

While everything was drying I decided to look for a boardview. I couldn’t find one for this particular card, but I did find one for the 760 from Asus. The elements I needed were in a different place, but armed with a multimeter I found the right ones. Finally I found a missing resistor and after soldering the resistor the graphics card started to show normal picture.

Hurrah, I’m almost at the finish line. After a half a day of testing I filled all problematic spots with greenery varnish, dried and assembled the video card.

I put the graphics card in for a few days test:

Types of batteries

In terms of design features distinguish between batteries in the form of sliders and rim.

Screwdriver battery in the form of a slider

But these are minor differences compared to the types of batteries. Both the slider and the rim are used in different types of batteries.

There are three types of screwdriver batteries:

The lithium-polymer batteries (Li-Pol) are not made for screwdrivers. Their main applications: smartphones, cell phones, tablets, laptops, radio-controlled devices, electric cars.

Nickel-cadmium batteries are the cheapest, fastest to charge, have over one thousand charge cycles. Batteries are resistant to operation at low temperatures. But they have a memory effect. So you can only charge them when they are fully discharged, otherwise the capacity will drop. They have a high self-discharge current. They are made of toxic materials and are difficult to dispose of. These batteries are the most in demand.

Nickel metal hydride batteries are more expensive, non-toxic, and have low memory effect. Higher self-discharge current than NiCd batteries. Capacity higher, charge cycle over five hundred. These batteries have a lower tolerance to high rates of discharge. They are less suitable for maximal use of the tool’s power. They must be constantly recharged.

Lithium ion batteries are more expensive, powerful, fast charging. They have no memory effect. Low self-discharge current. Battery cell voltage is greater, so there are fewer cells. Consequently the dimensions and weight of these batteries are smaller than those of the nickel batteries. But they must not be completely discharged, otherwise you have to buy a new one after a few such cycles. To improve the quality of lithium-ion batteries, manufacturers install a chip in the battery or screwdriver that monitors the battery. A multi-level, multi-stage protection is formed:

  • Against high temperature.
  • No more discharging. These batteries are afraid of total discharge and can not recover if the discharge is below the permissible level.
  • Against short circuits.
  • Against overcharging, as an explosion can occur.
  • Against overcurrents.

The control board installed in the battery case is more effective. When the battery is not in use and is not placed in the wrench, the IC monitors the battery and opens the circuit if there is a problem. The battery is fully protected.

Fault detection and recovery of the electric screwdriver battery

Before proceeding to repair the battery, you should determine its fault, otherwise the repair will be quite difficult or impossible. It should be noted that the failure of all elements of the battery at the same time is impossible, except in rare cases where there may have been a long-term short circuit of the output terminals of the battery.

To determine the malfunction follows:

  • Place the battery on charge and wait until it is fully charged.
  • After that disassemble the case, and measure the voltage of each charging cell. The difference in voltage across the banks for nickel-cadmium batteries may be in the range of 1.2-1.4 V, and the difference of lithium batteries may be about 3.8 V.
  • Banks that have less than the rated voltage should be marked. After that, the battery should be reassembled and given a full load until a noticeable discharge.
  • Then disassemble the battery again and measure the voltage of each cell again.
  • Usually the biggest voltage drop will be in the marked cells, which will need to be “reanimated” or simply replaced.

If the electric screwdriver requires 12 V to work, you can try to find the faulty elements in a simpler way. To do this:

  • Charge the battery fully, then take it apart and measure the voltage of each cell.
  • Then use a 12 volt light bulb to discharge it completely and measure the voltage of all the cells again to determine which ones are faulty.

Instead of a light bulb you can use a voltage matching resistor.

Repair and replacement of electric screwdriver battery cells

The most effective method of how to repair the battery of an electric screwdriver is to simply replace the failed charging cells that were found during their inspection.

To make the repair, you will need a donor, that is, a second battery, which also has failed banks, if this is not available, you can buy new cells online. There are plenty of online stores that are willing to deliver new batteries directly to your home by courier service.

Important. Acquired cells should have the same capacity and dimensions as the ones you are replacing.

The following things must be prepared for the repair: soldering iron, tin solder and spirit flux (preferably).

The process of replacing the charging cells itself does not provide any difficulty, just be skilled in soldering.

Electric screwdriver battery recovery

Warning. To avoid damaging the battery when working with the soldering iron, soldering must be performed quickly.

To connect the elements it is recommended to use the native plates, and if it is impossible to use them, replace them completely with the same size, but of copper. This is necessary for the correct charging process. With different cross-section of the connecting plates between the cells, they will heat up, and of course, to protect the charging banks will constantly actuate a thermistor.

Care must be taken when assembling the batteries. The connection should be sequential. the minus of each battery is connected to the plus of the next cell.

After all the cells are fully assembled, their potentials are aligned, as they will be different at this time. For this it is necessary to do a certain charge/discharge cycle. The repaired battery is fully charged, after which it should rest for about one day. After one day the voltage of all cells should be measured separately, and if the assembly has been done correctly, the voltage of each cell should correspond to 1.2 V.

After that the battery should be fully discharged again. For this purpose, the battery assembled, using an electric screwdriver, is given a full maximum load until it is completely discharged. The main thing is not to overload the electric screwdriver itself, so that it does not have to be repaired in the future. This charging/discharging procedure must be repeated several times in a row.

In the same way, about every three months, it is recommended to carry out a procedure to erase the “memory effect”, which will prolong the operation of the battery and the electric screwdriver itself.

Refilling with distilled water

Electric screwdriver battery recovery with refill should take place with a fully discharged battery. Ni-cd batteries are covered with paper. If vaporization has occurred, there will be visible traces on the surface.

After measuring the voltage, it is necessary to fully discharge all the banks with a 12 volt bulb. After that, the voltage is measured again. Those cells where it has dropped to 0.7 are faulty.

To fill the distilled water, it is necessary to make a hole in the side of the can. With a very thin drill (0,5-0,7 mm) make a groove. Make sure it does not go inside and damage the plates.

Using a syringe with a fine needle, pour a small amount of water. After that, the puncture must be sealed with epoxy or sealant.

Now the battery can be rocked. Each unit must be discharged again to zero by attaching a 1.5 volt light bulb to them. When the procedure is complete, the battery is reassembled and 5 cycles of charging and discharging must be performed.

How to replace the batteries?

The most effective way to repair the battery is to replace the failed bank. You can buy a new battery at any electrical store or remove it from another device.

Replacing a damaged bank: step-by-step instructions

Step one: you need to disconnect the faulty segment from the common chain. Since they are secured to one another with a metal plate, it is best to use a pair of wire cutters for this purpose. It is necessary to leave a strip of optimum length on each side so that it can be connected with a soldering iron without any problems.

Step two: now at an optimum distance from the other elements it is necessary to attach a new can to the chain. For this purpose we need a soldering iron. The only thing to keep in mind is that the “minus” is connected next to the “plus” and so on throughout the circuit. If the plate is not enough to connect the segments, it is replaced by a copper wire.

Step Three: Now all the battery parts need to be assembled in the same way as before.

Please note! It is desirable to equalize the charges on each bank by means of charging and charging several times as we described in the previous instruction. Then take turns measuring the charge level of the power sources, because they should always remain at the same value.

Exactly the same way you can repair a lithium-ion battery. In this case, the process is complicated only by the presence of an additional board, which is disconnected before starting the process. The defective banks can no longer be repaired, so they are replaced.

Repair of the battery of an electric screwdriver

Almost all electric screwdriver battery failures can be repaired by yourself. You will need to know the cause of the problem and how to fix it.

Detailed battery diagnosis: step by step instructions

Step one: You need to charge the power supply up to 100%. If it is a nickel-cadmium battery, it is first discharged to zero to avoid the “memory effect”.

Charging process of the battery of the tool

Step two: Then you need to remove the cover of the plastic block. It is much easier to do this if it is screwed on. you have to unscrew them. However, often this cover is fixed with glue, so you need to take a penknife and carefully go along the seam, after which you can easily detach the top part with a screwdriver.

The battery cover is held in place with screws or glue

Step three: now it is necessary to examine carefully the condition of the internal elements and detect any damages: chain damage, leaky electrolyte, etc.

Any external defects should be carefully examined

Step four: Then the voltage level of each bank should be measured with an ammeter. For nickel-cadmium and nickel-metal hydride sources there should be a voltage of about 1.3 V. For the lithium-ion batteries, the charge is. 3.7 V. It is advisable to sign the voltage level of each battery to avoid confusing them.

After the measurements have been made, the defective cells can be found

Step five: you should now make a load for the battery by attaching a small light bulb to the outputs. In this form the cans should be kept for some time, and then the voltage should be measured again with the device. Then it will be possible to identify the link with a high drawdown.

This way you can determine the voltage level of each bank

Once the defective cells in the battery have been found, the best method for repairing them should be chosen. There are two ways to do this:

  • Repair the defective banks by flashing with high voltage current or add filtered liquid inside in case of evaporation of the electrolyte. Nevertheless such measures will be enough only for some time and then the banks will have to be replaced.
  • To replace defective banks is the best way to solve the problem. If you want, you can take already used power sources, but working.

A faulty battery is repaired with an additional, powerful power source


Failure of power units occurs when screwdrivers are often used as a drill. Active overloading can cause boiling of the electrolyte inside the batteries. This can cause their casings to swell and the electrolyte to leak.

To avoid spending too much money for a new battery, you need to diagnose the old batteries. You can get by with just repairing the charging cells. Check the battery in this order:

  • Connect the battery to the charger.
  • After half an hour take a voltage measurement. Voltage value is usually 13 volts. After 2 hours the voltage at the battery terminals will be 14v. Finally the battery will show 17 volts.
  • If the current is 1 A or more after 60 minutes after starting to charge, the battery is in good condition.
  • Next check the battery under load. Usually connect a 40 watt bulb or take a 35 watt 12 volt car headlight bulb.
  • If after three minutes the voltage across the battery terminals will be less than 12.4 volts, then one of the batteries, or several at once, requires replacement.

Measuring the battery voltage

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