Fault definition
The most common cause of failure is the failure of only one element. They are connected in series, which means that even a drop in capacity on one battery will lead to a complete malfunction of the entire battery. In this case, we need:
- Screwdriver. Usually the body is connected with Phillips screws. Some models have foolproof protection and there may be vandal-resistant sprockets, triangles or even spanners.
- Multimeter. Any model is enough, even the cheapest DT-830. Since measurements are taken in millivolts, Soviet dial voltmeters will not work.
- The battery is disconnected from the screwdriver. It must be fully charged.
- The case is disassembled.
- Now you need to remove all the jars. There are more of them in Ni-Kd, since the nominal voltage of one section is less.
- Voltage is measured on each bank. For nickel-cadmium, 1.2 volts is nominal. For lithium. the normal voltage is in the range of 3.6-3.8 volts.
- After measuring, you need to look at which banks the voltage is reduced. For example, if the voltage is 3.8 on two lithium batteries, and 3.5 on one, it means that it is defective.
- The battery is assembled and installed in the instrument. Now she needs to be set to zero.
- The battery is disassembled and the voltage is measured again. If the voltage on the alleged element is much lower than on the others, then it is being replaced or repaired.
General repair recommendations
How to restore the battery of an electric screwdriver? You need to have an elementary understanding of electrical engineering. The battery circuit is idle. Ordinary serial circuit (plus connects to minus).
When repairing Ni-Kd, the following recommendations should be taken into account:
- They have a memory effect. The classic scheme for commissioning such batteries is 3 full charges and 3 discharges to zero. The new element must go through the same buildup.
- A similar item. So that it does not get knocked out of the chain and does not break the battery at all, the new element must fully correspond to the previous rating.
The lithium battery of an electric screwdriver can be repaired at home if you consider the following:
- They cannot be soldered. Intolerance to high temperatures will lead to a non-repairable condition. To do this, you need to use contact welding (it heats the electrode for a short time without harming the battery). If there is no access to CS: GO, soldering with a very powerful soldering iron from 100 watts is allowed. Movement must be fast and accurate.
- Identical models. Now there are several main manufacturers of lithium batteries, which are used in popular foreign models of screwdrivers, such as Hitachi, Makita and domestic ones: Interskol, Zubr.
Topping up with distilled water
Rebuilding the battery of an electric screwdriver with topping up should take place with a completely discharged battery. Ni-Kd batteries are covered with paper. If there was evaporation, then there will be noticeable traces on the surface.
After measuring the voltage, you need to completely discharge all the banks using a 12 volt bulb. After that, the voltage is measured again. Those elements where it dropped to 0.7 are faulty.
To fill in distilled water, you need to make a hole in the side of the can. A groove is made with a very thin drill (0.5-0.7 mm). You need to make sure that it does not go inside and damage the plates.
A small amount of water is poured with a syringe with a fine needle. After that, the breakdown must be closed with epoxy resin or sealant.
The battery can now be rocked. Each unit must be discharged to zero again by attaching 1.5 volt bulbs to them. When the procedure is over, the battery is collected and it is necessary to carry out 5 charge and discharge cycles.
Replacing cans in the battery
How to repair the battery for an electric screwdriver? The easiest way to revive the battery is to replace one of the cans.
It is necessary to find a defective element with a low voltage. To do this, you need to use a tester.
Instructions on how to check the battery of an electric screwdriver with a multimeter:
- A conventional multimeter has two test leads. a red and a black one. There are two contacts (plus and minus) from opposite ends of the can.
- The tester selection lever is set to “constant voltage” mode. If the multimeter has an automatic selection of values, this is enough. If it is not there, you need to put the lever in position “20”.
- Probes are applied to the contact pads and the voltage is measured. The real voltage is shown on the screen. If there is a “-” sign in front of the numbers, then the probes need to be changed with each other.
- Each bank is checked using this algorithm.
When a broken element has been found, it is simply soldered off and replaced. You need to use a powerful soldering iron so as not to overheat the jar.
How to repair an electric screwdriver battery at home
The cordless electric screwdriver is a handy mechanism that allows you to quickly deal with repairs. Instead of a heavy drill on a wire, it is better to take a lightweight screwdriver that can handle the same tasks without being tied to one place.
They have one problem. batteries fail. There are many reasons for this:
- Long downtime. Modern lithium-ion batteries require periodic charging and discharging. They drastically lose capacity if they are idle for a long time.
- Temperature drops. Li-ion does not tolerate high temperatures well. Therefore, there are recommendations for storing these batteries in the refrigerator. But they cannot work in such conditions.
- Overdischarge. The protection system can cause the batteries to discharge to zero and a large current must be applied to the input to resurrect them.
Repair and replacement of battery cells
Do-it-yourself electric screwdriver battery repair can be more extensive. For example, conversion of Ni-Kd to lithium ones. To do this, you need to purchase several Li-ion batteries and a charging board. The number of batteries must correspond to the original voltage rating.
As practice shows, most screwdrivers can be easily converted from one type of battery to another, without any problems. With increased exposure, resistance to constant use and higher capacity, your old electric screwdriver will last much longer.
Replacing cans in an electric screwdriver battery
To repair the battery, you need to purchase cans of the same voltage. They can be taken either from an old and faulty battery, or you can purchase new ones. per can.
It’s important to know! The purchased item must match in capacity and dimensions with the rest of the banks.
At home, you can replace a faulty element with a soldering iron and tin. In production, such a connection is carried out using spot welding. Buying such a device for repairing an electric screwdriver battery is irrational. After the defective element is replaced, you can assemble the battery and check the quality of the repair, for this you need to put it to charge until it is fully charged. After that, and a few hours after the device has cooled down, you will have to disassemble it again and measure the voltage on each bank. Voltage values should correspond to 1.2-1.3V.
It is better to operate batteries for screwdrivers following the instructions. Discharge Ni-Cd batteries to 0 before the next charge, and recharge Li-ion batteries as often as possible. Only dry nickel-cadmium cells are subject to partial recovery, lithium-ion cells are not subject to recovery. Handle batteries with care!
In this article, which we will conditionally divide into three parts, we will consider: the types of batteries that are used in screwdrivers (part 1), their possible causes of failure (part 2) and available repair methods (part 3).
Item-by-item check
This method requires disassembling the battery case. It is used when the battery or its cell stops delivering good current and recovery attempts fail. One bad link is enough here, since they are connected in series. But to find such an element, you need to check the internal resistance of each of them.
Of course, you need to start with a general inspection of all the cans: are there any cracks, leaks, etc. A defective element will immediately give itself out in appearance.
The current return test is performed using Ohm’s law for a complete circuit (aka the first Kirchhoff’s law). To do this, you need to take a resistance with a nominal value of 10 ohms, designed for 25 watts, and an ammeter. The element under test is short-circuited to a resistance connected in series with the ammeter.
For example, suppose a current of 100 mA is obtained for a 1.2 V Ni-Cd battery. Let’s write it down and re-measure, but not the current, but the voltage across the element. First, we will measure the open voltage, without connecting a resistor, and then connect the resistor and see how much the voltage has dropped. Let the first time it was 1.2 V, and after connecting the resistor it became 1.05 V. Then the internal resistance of this element: This is not too little, if all the elements are like that, then the battery can provide an electric screwdriver with only half the power. The lower the internal resistance, the better the element, but with an indispensable condition: it must give a nominal, or close to this voltage. If the voltage is too low, or very close to zero, then the element is short-circuited, it is not suitable and cannot be restored. If the internal resistance is more than 3 ohms, then you can try to restore (see below) or replace.
Eliminating the memory effect
This recovery method is applicable to nickel cadmium batteries. It is very simple to execute. First, the battery is discharged completely with an electric screwdriver or other load such as lamps or resistance. Then it is fully charged. And this must be done several times. If the battery has no other defects, then it will fully recover. There is no point in restoring lithium-ion batteries in this way.
There are ways to “restore” asymmetric current, when the charging current pulse is larger, and the following discharge gap is smaller, so that the difference is positive. This method is incorrect, it does not take into account the fact that chemical processes are much slower. Even more wild is the method of recovery with high current pulses. You shouldn’t use them.
To restore a Ni-Cd battery, you will need:
- Charger;
- Several car bulbs;
- Copper wire 0.5 0.75 mm.kv;
- Multimeter.
It is better, of course, to have an uncomplicated special stand for restoration, but this is more suitable for professional repairmen than for ordinary users of screwdrivers. But be that as it may, working with two multimeters is much more convenient than with one.
The recovery steps are as follows:
- Determine the minimum, nominal and maximum battery voltage.
- Determine the rated load current.
- Turn on the switch S1 to position P (discharge). If the current is low, you can slightly increase the load by adding a few bulbs.
- Wait until the voltmeter shows the minimum voltage.
- Turn switch S1 to position З (charge). Monitor the current during charging.
- Wait until the voltmeter shows the maximum voltage.
- Switch S1 to position 0.
- Wait 20-30 minutes.
- Switch S1 to discharge position.
- Go to step 4.
- Repeat steps 4-10 until the discharge current is less than the rated load current during the normal operating time of the electric screwdriver.
In practice, do 3-4 to 7-8 cycles. If condition 11 in the recovery algorithm cannot be reached, then the battery must be repaired.
Types of batteries and their differences
Of all the types of batteries that the industry produces, only three types are suitable for these criteria:
- Ni-Cd. nickel-cadmium;
- Ni-MH. nickel metal hydride;
- Li-ion. lithium-ion.
Nickel-cadmium appeared earlier than all others and showed good performance properties. Such a battery has a voltage of 1.35 V… 1.0 V. Here and further we denote the first nominal voltage, and the last. the voltage at the end of the discharge cycle. Ni-Cd have a number of charge / discharge cycles in the range of 100. 900, it depends on the quality of the materials and the mode of operation. Ni-Cd is also characterized by a very low internal resistance, they almost do not heat up during charging, they are stored for a long time.
- “Memory effect” interfering with operation.
- Cadmium toxicity, it is a strong carcinogen.
Another type: a nickel-metal hydride battery. These batteries have been proposed as a replacement for Ni-Cd. The rationale was the shortcomings of traditional cadmium batteries. In theory, Ni-MH is good: it has a high energy capacity (up to 300 Wh / kg), is not subject to the memory effect. Voltage 1.25 V 1.1 V, the number of charge cycles 300-800. Old type Ni-MHs are completely self-discharging after a year of storage. It is recommended to store them at a low temperature, from 0 to 20 degrees Celsius. Batteries of a new type LSD Ni-MH (Low Self-Discharge), as their name indicates, have a low self-discharge and heat up less when charging.
How to Repair a weak Drill / Screwdriver / Battery runs out quickly
Disadvantages: Ni-MH batteries are 10% discharged during the first day, and significant heat generation during charging.
Li-ion batteries have a voltage of 3.7 V 2.5 V, but in reality it is a little more complicated with it, it all depends on the mode of use of the battery. The number of charge cycles is approximately 600, but this is provided that no more than 20% of the capacity is taken from the battery. Lithium-ion batteries do not like deep discharge. From this they quickly fail. The internal resistance of Li-ion is very small, 5 15 milliohms. Self-discharge about 1.6% per month with full charge and no load.
Bosch GSR Lithium-Ion Cordless Drill Driver Opening/ Repair and Look Inside
Disadvantages: high cost, limited shelf life, not dependent on use. Risk of explosion and fire if improperly handled.
Load method
This method is similar to the previous one and is perhaps simpler. No need to disassemble the charger, or use a laboratory power supply. You only need:
- Car bulbs;
- Multimeter;
- Pieces of wire;
- Soldering iron with solder and flux.
How to Repair Electric Screwdriver
Test scheme: For such a test, you must first put the battery on charge and charge in the usual way. Then the rated load is applied. It is not difficult to find out the current, for this divide the power consumption by the rated voltage. For example, if an electric screwdriver consumes a power of 50 W (a typical case), at a voltage of 18 V, then the current should be 50/18 = 2.77 A. To achieve such a current, or close to it, you can dial in parallel car bulbs from turns.
If the battery delivers the rated current for several minutes, the voltmeter shows a voltage slightly lower than the rated voltage, and the bulbs do not fade, then the battery is in good order. However, it may happen that for Ni-Cd the current will soon begin to weaken. This is a manifestation of “memory”. In this case, you need to carry out the restoration. Lithium-ion batteries do not have a memory effect, although in theory it exists, in practice it is believed that it simply does not exist.
Repair and replacement of battery elements for an electric screwdriver
It should be noted initially that all types of batteries, both nickel-metal hydride and lithium-ion, are subject to repair. Not many people know how to repair the battery of an electric screwdriver, so very often it is faulty batteries that become the reason for buying a new tool.
It is not possible to repair a can that does not hold a charge, so it will have to be disposed of after being removed from the circuit. It is irrational to repair the battery with an electric screwdriver, in which more than 4 faulty cans are found. In this case, it is easier to purchase a new battery entirely, or find a used device.
In conclusion, it should be noted that most screwdrivers are equipped with two batteries, so if one fails, then the second will have to be used more intensively during its repair. This will allow you not to lie idle with the tool, and you can try to repair the product at a convenient time.
Skipping conversations about the benefits of screwdrivers, you can go straight to the topic. The battery or rechargeable battery is the biggest concern for screwdriver owners. It is better to handle them strictly according to the instructions. In the event of a breakdown, there is only one solution. to buy a new battery. However, you can temporarily try to use the problem battery, for which there are some tips here. We emphasize that battery repair is a temporary solution, but first you need to accurately investigate the causes of the malfunction.