How to fix your dead NICad Batteries for FREE!!

I came across this helpful fact on Pinterest and yet I have not tried it I do find it very helpful and could save myself or other folks with these types of batteries a lot of money. I always thought that once a battery on a power tool is dead that there is no way to save it. I am not sure if this works with lithium batteries because its a completely different type of battery. You could try it but don't expect the same results.

I pulled this info from Superior Remodeling L.L.C Kitchen and Bath Experts website.
The Principle

Nickel Cadium (nicd) batteries have a tendency to grow internal whiskers called crystal dendrite growth. Those whiskers prevent the battery from holding a charge. This often happens due to overcharging. The growth can be blasted away with a quick jolt from car batteries, DC power supplies, or even a welder do the trick. The process revives the cells or batteries by the injection of a short duration, high-magnitude, zap of current through them.

The Procedure

Most nicd batteries require 24 volts of zap to clear them out. Most people use two 12 volt car batteries  for the jolt, which produces 24 volts total when wired together as shown below but any 24 volt source will do. A good car battery charger will work, but only if it has a strong boost mode. If it doesn't, a car battery and a car charger wired together in series as shown below will work. I've even heard of people snapping 3 little 9 volt batteries together for the juice, But I haven't tried that yet. An AC welder will work also, though probably not too many of you have a welder at your disposal. For tool batteries under 9.6 volts, one car battery or a 12 volt equivalent is sufficient.

Use the same concept when using 12V batteries

How long you zap your tool battery depends on the voltage of the rechargeable. The chart above shows the different surge times, but first let's deal with how to wire the car batteries together.

Wire your two car batteries in series. You can use common jumper cables if desired, or use lamp chord and a couple of alligator clips or anything that will keep temporary contact will work. Any wire will do as its not drawing very high voltage.

Explanation of series wiring

Series wiring is where two or more sources are hooked together in series (i.e. positive terminal of the first buttery is hooked to the negative terminal of the second battery). The resulting voltage is the sum of the individual battery voltages. If two 12V batteries are hooked together, the resulting voltage will be 24V.

There is no danger connecting batteries in this way. In fact, it's quite commonly done. This principle can be seen in everyday flashlights where the positive of one battery is butted up against the negative of the next battery. It produces the some of their voltage