DIY tool battery replacement and repair

Recommendation points

• Reasons for battery failure
• Recovery “run” of the battery
• How to open a case without breaking it
• Replacement of cans or their restoration
• Secrets of long-term operation

Batteries in tools often fail earlier than mechanism parts. This article will help to solve such a problem, in it we will tell you about the secrets of rebuilding and repairing batteries with our own hands, as well as some ways to extend the life of nickel-cadmium batteries.

For repair professionals using proprietary tools, batteries are just consumables. Over time, the battery capacity drops, and it is simply changed, since the components can be found quite easily. But this does not apply to cheap tools: sometimes it is almost impossible to find a suitable battery, it remains either to say goodbye to the tool, or to resort to self-repair.

Reasons for battery failure

Despite the wide variety of batteries, they all have a typical device and are easy to repair. The plastic case is just an outer shell. Inside it is a bundle of 10, 12 or 15 series-connected 1.2 V nickel-cadmium batteries, for batteries with a total voltage of 12, 14 and 18 volts, respectively. Batteries, commonly referred to as “banks” by the common people, are arranged in two tiers: there are usually two in the top, the rest are compactly grouped in the bottom.

Battery breakdowns can be mechanical or electrochemical in nature. The first type includes the destruction of the cans themselves or contacts and soldering points, as well as a short circuit between batteries due to a violation of the insulating plate. Such breakdowns occur due to a strong shock or flooding, the battery shows no signs of life, there is no voltage at the input. To make repairs, the battery will have to be disassembled.

The second type of malfunction occurs due to degradation of the batteries, arising from improper use, improper charging and use, or simply due to old age. The battery shows a voltage of 3-5 V, which can rise to 8-9 V after charging, which is enough for a very short operating time. If the battery has been in this condition for more than a year, disassembly is likely to be required. In other cases, it is enough to “overclock” the battery with a special procedure.

Recovery “run” of the battery

To work with batteries, it is advisable to purchase a charging and balancing device (ZBU) with a controller, for example, HobbyKing ECO6 or similar. Its cost is equivalent to buying a new battery, it is also useful in everyday life for charging and restoring various types of batteries, including from laptops and phones.

With great difficulty, but also realistic, to use two digital multimeters and a power supply with an adjustable voltage output, connected through a rheostat. One multimeter in the current measurement mode is connected in series with the power line, the second is connected to the battery terminals to monitor the voltage at the poles.

To “wake up” the battery, it is necessary to apply double voltage to the power terminals and set the current to a third of the capacity value. That is, for a battery with a capacity of 2 Ah with a voltage of 12 V, a voltage of 25 V is needed at a current of 600-700 mA. After two to three minutes of charging, the battery must be disconnected and the voltage at the terminals must be checked several times at intervals of 10-15 minutes. If during these periods no drop of more than 0.1 V was observed, an increased voltage is applied to the battery again at a current strength of 70% of the capacity, this time the charging time is 4–5 minutes. After the “run”, the battery should be completely discharged using a rheostat, setting the current to 0.5–0.7 A, and charged. The cycle must be repeated 2 to 7 times to eliminate the memory effect.

The charger will do all these operations automatically, including the required number of charge / discharge cycles. If the battery, for one reason or another, cannot be “driven out”, the charger will notify you of this and you will have to disassemble the case to replace one or more cans.

How to open a case without breaking it

The cheapest batteries have a collapsible case, the lower and upper halves of which are tightened with four self-tapping screws. But there are also hulls that seem solid at the first examination, their halves are glued or soldered.

To open such a case, put the battery on its side and hit the joint with a rubber mallet, periodically checking if the seam has come apart. After several minutes of such manipulations, the body should split, or a visible gap will appear at the joint. You can insert a section knife blade into it at an angle and slightly hammer it with a hammer deeper. If you do this from 3-4 sides, the layer of glue will crack and the halves will be able to separate.

When the case is disassembled, the battery bundle will remain at the top. To remove it from there, bend the contact plates slightly. In the upper part of the battery there may be a head with a thermocouple; to remove it, you need to either unbend the plates of the outermost batteries, or unsolder them.

There are two insulating gaskets between and below the battery tiers: these must be retained for reassembly. After the battery is repaired, a cap is put on it and inserted back, connecting the two halves of the case with cyanoacrylate.

Replacement of cans or their restoration

The battery loses capacity and discharges by itself due to the presence of even one faulty jar in the bundle. Therefore, you need to check each element of the circuit by applying the multimeter probes to the battery terminals in the appropriate polarity. “Silent” batteries have practically no voltage, do not respond to their “run” and even to pulse heating with high (5-7 V) voltage. Such elements are exchanged for new ones (they are commercially available), or one battery is assembled out of two.

In 90% of cases, batteries fail due to drying out and can be relatively easily brought back to life. To do this, a very small hole with a diameter of 0.2–0.25 mm must be drilled at the end of the negative contact. It is enough to pour 1-1.5 cm into it with a syringe³ distilled water and let the elements rest at room temperature for 3-4 days. After that, you can start running each battery separately, by analogy with a whole battery. The entire battery can be charged and discharged; you do not need to unsolder them to work with individual elements.

If the battery is back to life, add another 0.2-0.3 cm³ distillate and seal the hole with tin. It is necessary to restore the damaged paper shell with electrical tape, then collect the batteries in a bundle and fasten them together with tape or hot glue.

Secrets of long-term operation

There are some simple ways to achieve a longer battery life. Above all, do not use the tool and do not store the battery at temperatures below 6–8 ° C. Also, do not overload the battery, allowing for overheating. If the power drops by more than half, it is necessary to replace the battery, and 2-3 full discharge-charge cycles should be carried out once a month and a half of active operation.

The batteries of the screwdriver can be stored in a discharged state, but it is better to do this with a connection to the ZBU operating in the appropriate mode. The device will also help you to perform several charge-discharge cycles at the optimal current parameters for your battery..