battery screwdriver repair their own hands

The cost of a new screwdriver by about 70% of the cost of the battery to it. Not surprisingly, when faced with the failure of the battery, we ask ourselves the question - what's next? Buy a new battery or a screwdriver, and maybe it is possible to produce a battery screwdriver repair their own hands and to continue the work already familiar tool?

This article, which is divided into three parts, we will consider: the types of batteries that are used in the screwdriver (part 1), the possible causes of failure (Part 2) and affordable ways to repair (part 3).

screwdriver Battery: design and types

It should be noted that regardless of brand screwdriver and country of origin batteries have an identical structure. Assembled battery pack has such a form.

If we analyze, we will see that it is assembled from smaller components, which are assembled in series. And we know from school physics course, that the elements that have a serial connection, slazhivayut their potentials.

Note. The amount of each food item and gives us a final charge from the battery contacts.

Matched portions or "banks", usually have a standard size and power, they differ only by the capacity. Battery capacity is measured in A / h and is indicated on the element (shown below).

The following types of elements used for the arrangement of screwdrivers accumulators:

  • nickel - cadmium (Ni - Cd) batteries with a nominal voltage on the "banks» 1,2V;
  • Nickel-metal hydride (Ni-MH), cell voltage - 1,2V;
  • Lithium-ion (Li-Ion), with a voltage - 3,6V.

Consider in more detail the advantages and disadvantages of each type.

Ni - Cd

Pros:

  • The most common type because of its low cost;
  • Not afraid of low temperatures, such as Li-Ion batteries;
  • Stored in a discharged state, it retains its characteristics.

Minuses:

  • Only in the countries of the "third world", due to the production of toxicity;
  • Memory effect;
  • self-discharge;
  • Small capacity;
  • A small number of charge / discharge cycles, so long did not "live" during intensive use.

Ni - Mh

Pros:

  • Environmentally friendly production, it is possible to acquire a high-quality brand battery;
  • Low memory effect;
  • Low self-discharge;
  • Large capacity, as compared to Ni - Cd;
  • A greater number of charge / discharge cycles.

Minuses:

  • Price;
  • It loses some of the characteristics during prolonged storage in a discharged state;
  • long "live" at low temperatures.

Li-Ion

Pros:

  • No memory effect;
  • Almost no self-discharge;
  • High capacity battery;
  • The number of charge / discharge cycles many times more than that of the previous types of batteries;
  • To set the required voltage necessary minimal number of "cans", which substantially reduces the weight and battery size.

Minuses:

  • The high price is almost 3 times compared to nickel - cadmium;
  • Three years later, there is a significant loss of capacity, because Li decomposed.

With elements we met, move on to the other elements of the battery pack screwdriver. Disassembly unit, e.g., for repair screwdriver battery Hitachi (depicted below) is very simple - unscrew screws around the perimeter and sever body.

The hull has four pins:

  • Two police, "+" and "-" for the charge / discharge;
  • Upper control, it is enabled through the temperature sensor (thermistor). A thermistor is required to protect the battery, it disables or limits the charging current when exceeding a certain temperature elements (typically in the range of 50 - 600C). Heating occurs due to high current during forced charge, so-called "fast" charging;
  • So-called "service" contact, which is incorporated by 9Kom resistance. It is used for sophisticated charging stations that line the charge of all the battery cells. In everyday life such stations to anything, because of their high cost.

That's actually the whole battery design. Below is a video on how to disassemble the unit.

fault location

With the appointment of the battery design elements sorted out, now look at how to define the problem, it is part 2 repair screwdriver battery. Immediately, we note that all the elements at once damaged can not, and since we have a chain in series, the output of one element - the whole chain does not work. So our task is to determine where we have in the chain the weakest link.

To do this we will need the meter, and the second method of troubleshooting lamp 12V, if your battery at the same 12 volt screwdriver. Proceed as follows:

- We put the battery on charge, waiting for the signal of a full charge.

- Parse the housing and we measure at each battery bank. For Ni - Cd we should be 1.2 - 1,4V, in lithium - 3.6 / 3,8V.

- Celebrate all the "banks", in which the voltage is less than the nominal. For example, most of the elements Ni - Cd voltage of 1.3V, and at one or more - 1.2 / 1.1V.

- Putting the battery and operate to a significant loss of power.

- Remove, dismantle, and we measure the voltage drop across the "Bank" accumulator. On selected items "subsidence" of the voltage will be greater than on the other. For example, they do not 1.2V, and 1.0V or even lower.

Note. The difference between the elements in the battery 0.5 - 0.7V considered essential, which means that the element comes into disrepair.

Thus, we have found a candidate for the "resuscitation" or "amputation" and replace with new elements.

If your screwdriver is powered by 12V or 13V, you can search for a simpler method. "-" completely "+" and a charged battery is disassembled and the contacts connect 12 volt lamp. The lamp will load and will discharge the battery. Next test is performed on the battery cells, where most of all the voltage drop, and there a weak link.

There are other ways, instead of the lamp can pick up resistance, but it has needed the basics of electrical engineering, and it is doubtful that would be necessary with resistor was at hand.

Other faults are very rare. For example, loss of contact locations in the soldering unit batteries or power contacts, failure of the thermistor. This Problem longer inherent in counterfeiting. In view of the rarity, to focus will not confine ourselves to the battery cells.

With the "problematic" elements sorted out, it is necessary to repair. How to repair screwdriver battery? Generally available to repair 2 ways, so to speak. This restoration and replacement of items that have become worthless.

Is it possible to "revive" the elements and how?

Proceed to Part 3 of the battery repair screwdriver and immediately specify that the concept of "intensive care" for lithium - ion batteries are not applicable. Memory effect they have, most likely, was the expansion of lithium, and this has nothing to do about it. In these batteries need to find out what the cause of the problem: the element or control circuit. There are two options:

  • change control circuit from the other, but similar to ours, the battery if help - find a replacement and change;
  • 4V apply to the element with a current of about 200mA, this requires controlled charger. If the cell voltage increases to 3,6V - defective element, the problem in other elements, either in the control circuitry.

Reconditioning screwdriver battery is available primarily for Ni - Cd batteries, but they are, as a rule, and the most common in household screwdrivers.

So, how to revive the battery screwdriver? There are two kinds of "intensive care" for these types of batteries:

  1. compacting or compression method (it will work in cases where the electrolyte is still available, but the volume is lost);
  2. "Firmware" voltage and current of the great nominal. This method makes it possible to eliminate the memory effect, and although not completely, but to restore the lost capacity.

This method is shown below in the video.

Note. As a rule, in nickel - cadmium batteries are the main cause of loss of capacity - electrolyte boil-off, and if it is critically low - no "firmware" will not help.

This method, if the result is positive, the output will not solve the problem of building elements. Rather, it would only postpone the replacement of worn-out and in the future will still need repair screwdriver Makita battery or any other.

Repair and replacement of elements screwdriver battery

More effective way to repair the battery for the screwdriver - the replacement of items that we identified as being faulty.

For repairs we need a battery - "donor", in which some of the elements intact, any new "banks". Buy them not be easy, even on the Internet you can easily find a dozen shops that are ready to send these items by mail. Price is not particularly bites, such as nickel-cadmium cells with a capacity of 2000 mA / h costs around $ 100.

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Note. By purchasing a new item, make sure that to its capacity and dimensions coincide with native elements.

So do we need a soldering iron, malokoroziyny flux (preferably alcohol on rosin flux), and tin. About spot welding does not say, as for the repair of single battery is hardly any need for her to acquire or collect ...

In the most difficult to replace anything not, especially if at least some - that have experience in soldering. In the photos all in detail is shown, cut the defective item, a new sealed his place.

It is necessary to note some nuances:

  • soldering soldering iron, solder, try quickly, so the battery would not heated, because risk to spoil it;
  • if possible connection is realized with the help of family plates, or use of the same size made of copper, it is important because charging currents and large at the wrong section of connecting wires they will bask respectively will fire protection thermistor;
  • in any case, do not mix battery plus-minus - series, then minus the previous bank is on plus the new banks, and less new - in the next plus.

Once welded together the new elements must be potential equalization on the "banks", because they are different. We perform charge / discharge cycles: charge set overnight, giving a day to cool down and we measure the voltage on the elements. If we did everything correctly, the picture will be like this: all the elements of the same figure multimeter, within 1.3V.

Next, we proceed to the discharge of the battery, insert the battery into the screwdriver and load it "in full". Main mercy on himself screwdriver, otherwise you'll have to repair it as well. Bring to full charge. This procedure was repeated two more times, ie, charged and fully discharged.

It should be noted that the erasing procedure the "memory effect" should be carried out every three months. It is analogous the above exercise.

This is not very tricky procedure to extend the work of your screwdriver, at least as long as he himself does not have to change to a new