Electric drill battery recovery

Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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After several years of proper operation, your screwdriver-drill began to "mope" - the charge of the battery (battery) runs out quickly, you have to recharge it often, and to do this, interrupt work. Loss of battery capacity is inevitable during intensive use (depending on the number of discharges-charges) and over time. By the way, if a screwdriver is rarely used, the battery capacity also decreases by itself (especially if it is stored uncharged), and after a year, it can decrease by a quarter or even more. But in many cases this happens prematurely and because other dangers lie in wait for the battery. So, it will inevitably deteriorate if you use the tool at an ambient temperature below 0 ° C and above +50 ° C, as well as in rainy weather and in conditions of high humidity, especially if water gets inside.

One of the main reasons for the gradual loss of capacity is sulfation, that is, oxidation inside the cell. All this leads to an increase in its internal resistance, and, as a result, to the unsuitability of the latter for use in a screwdriver. Such a malfunction can be detected even visually after disassembling the battery case of a screwdriver: those subject to corrosion or sulfitation will have a yellow-white powder on the surface, and elements affected by moisture, even after drying, will no longer work normally.

It is possible to determine whether the battery has lost its capacity (a battery can also be called a block, since it is considered non-separable), without "opening" and without devices: a serviceable battery heats up slightly when charging - up to about 30 ° C, and a battery that has lost capacity is very noticeable to the touch - up to 50 ... 60 ° C.

If the battery of the screwdriver has lost a lot of capacity, it has to be replaced. Then the question arises of buying a new battery pack.

In our time, the issue of the availability of spare parts for sale (including batteries) may seem superfluous. But not in all cases.

Elements from the disassembled battery case of the Hammer ACD120A screwdriver

Determination of a faulty element by a tester

The problem is that buying a separate battery pack for screwdrivers is a very difficult task, even in large cities, not to mention rural areas (the exception is specialized workshops and service centers where they can sell a refurbished battery pack "from old stock"), In addition, the battery packs are not unified and only “their own”, branded ones are suitable for each drill, since manufacturers prefer to create their own shapes and battery cases, and in addition, change them when developing the next modification. In addition, a separate purchase of a new battery is comparable to the cost of the tool itself (price: one and a half - two thousand rubles), so the following recommendations for self-restoring the drill battery, I hope, will be quite useful.

Before starting repairs by opening the battery pack, it is necessary to charge the battery as much as possible. Then disconnect the block from the screwdriver and disassemble its hard plastic case, carefully removing the cover with a screwdriver (if the cover latches are damaged when opening, you will later need to fix the battery cover with instant glue).

Resuscitation of a standard battery is possible with the help of elements of another, sometimes even older one, and even from another screwdriver, since the internal structure of the battery for most of these tools is identical. Therefore, it does not matter what model and brand of drill is available. The "donor" battery must also be fully charged.

Batteries consist of individual Ni-Cd (nickel-cadmium) cells with a nominal voltage of 1,2 V each and an energy capacity of 1200-1500 mAh.

To draw up practical recommendations, I dismantled the batteries of German DWT ABS-12 and Hammer ACD120A electric drills - both with a nominal voltage of 12 V. I put aside the DWT screwdriver two years ago due to a clear loss of power consumption of a regular battery. Instead, a new Hammer ACD120A screwdriver was purchased at the same time, the battery of which was enough for exactly two years.

After dismantling the battery cases, it turned out that the battery cells of the Chinese company Yang Guang are comparable in size and electrical performance to Huanyu batteries.

If the total voltage of the battery is 12 V, respectively, there are 10 series-connected battery cells with a nominal voltage of 1,2 V. In other cases, for example, 9,6 V or 14,4 V, the number of such "built-in" barrel elements will be others (8 or 12 respectively).

After charging the battery and then disassembling its case, I determined the faulty elements - using a tester (in this case, I use the popular M830 digital tester).

A pre-charged working cell in a battery of batteries at its poles will show a voltage close to the nominal, that is, about 1,2 V. For "sour" cells, the potential difference is close to 0 V.

By sequentially measuring the voltage on each battery cell and its internal resistance (if appropriate devices are available), it was easy to identify batteries that are unsuitable for further use (the greater the variation in voltage across the cells, the worse the quality of the entire battery).

When resuscitating the battery, I left for further operation those elements whose voltage was 1 - 1,2 V. I rejected the rest. In place of faulty elements, or, better, those that have lost their energy intensity, I connected the elements that retained their energy intensity to the maximum from another battery.

At the next stage, with the help of side cutters (or wire cutters), I removed the metal jumpers between the elements, removing the elements that had lost their capacity. Then, in their place, an old but suitable element from another batch (battery) was installed.

To solder the jumper to the "new old" (replaced) element, you will need a soldering iron with a power of at least 40 W and soldering acid.

The usual solder type POS-61 and rosin are indispensable here: the soldering is broken when the jumper is bent. And with the help of soldering acid, you can well irradiate the contacts before soldering the jumper and achieve greater reliability.

After replacing all the elements that lost their capacity, I assembled them in reverse order into the battery case of the screwdriver.

At the end of the work, I installed the battery case cover in place and carefully fixed it with Super-Moment glue (you can use another, suitable one).

Break in the battery cell circuit

Well tinned contact

Assembled and reanimated "old-new" battery for the Hammer ACD120A and DWT screwdriver and the remains of the DWT ABS-12 battery

After that, the tool will serve for a long time. My battery restored in this way ensured a fairly intensive operation of the screwdriver for almost a year and a half.

Using a similar method, you can restore batteries for portable radios, for example, I also restored the battery box for the Icom V8 radio, consisting of nine AA Ni-Cd cells and a nominal voltage of 1,2 V - simply replacing the cells that lost their capacity with new ones, only that purchased finger batteries. Thanks to this, the BP-207N battery did not have to be thrown away (a new one costs almost 1200 rubles).

In this case, such savings are justified, taking into account the fact that little time is spent on resuscitation (recovery): only 30 - 40 minutes.

In an old, battered battery, there may be several defective cells at once. When examining a battery that had not been used for two years, a good half of the cells turned out to be unusable for DWT.

After the replacement operation, the remaining good donor battery cells can be saved for future resuscitation.

Author: A.Kashkarov, St. Petersburg

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