Bringing dead nickel-cadmium batteries back to life

Very often, nickel-cadmium batteries refuse to charge at the moment when it is so necessary. They are especially capricious and do not tolerate neglect. They may fail for the following reasons:

• -Recharge.
  
• -Were in a discharged state for too long.
  
• -Exposed to excessively high temperatures.
  
• -Temporary effect.

But it's not that scary. And at least half of all batteries can be brought back to life and made to work again. To do this, you can assemble a recovery installation from an old camera. It just has a high-voltage generator with a storage capacitor. The point is to “puncture” the battery with a very high current pulse, which will “stir up” the internal processes and force the battery to take and release its charge again.

Will need

• ni-cd batteries.
  
• Old film camera with working flash
  
• Wires
  
• Switch.
  
• Button.
  
• Battery holder.

The process of creating a device for restoring ni-CD batteries

We disassemble the camera and remove the cover.

We separate the board from the case.We solder pre-tinned wires to the button that fires the flash.

And then we solder these wires to the switch.

This switch will be needed later to completely discharge the internal capacitor with the flash.
We also solder wires to the output of the storage capacitor. Before this procedure, be sure to make sure that there is no charge on it - shorten it with a screwdriver, for example.

Next, we solder these wires in series with the button and the battery holder. The plus from the capacitor goes to the plus of the battery.

The recovery process itself

So, we insert the batteries for power into the board holder - the converter will be powered from them. And we insert the ni-cd battery into the holder for restoration.

Then turn on the board's power. Usually you can hear the squeak of the transformer operating. You need to wait until the capacitor is fully charged (for this, most models have a special Light-emitting diode). As soon as everything is charged, press the button connecting the battery and capacitor circuit. You will hear a strong click - this is normal. It even happens that the button contacts may stick.
You can repeat this procedure 1-3 times in a row and then immediately put the battery on charge.

Conclusion

As I already said, most practically dead batteries can be brought back to life. Be careful: the capacitor charges up to 300 V, which is definitely life-threatening.
You should also not use very thin wires, since the peak current can reach 1000 A, because there is practically a short circuit.
After all the procedures, close the flash switch and turn off the power to the entire board.
Original article in English