How to Resurrect NiCAD Batteries in Cordless Tools

Updated March 23, 2017

Nickel cadmium (NiCd) batteries remain fairly common for use in cordless power tools, despite a lithium-based battery's ability to produce more power, last longer and weigh less. Price may form part of the reason; NiCd batteries are the least expensive type of rechargeable battery. A major benefit associated with NiCd batteries is that you can often resurrect them; you can't do this if you have a lithium-based battery.


Always charge your NiCd battery to initiate the resurrection process. Place it in the charger and let it charge until the deavice indicates it's full. It's unlikely to take more than about 30 minutes; and even when your charger indicates the battery is full, it still doesn't retain the charge it could when it was new. Turn off the charger, once the devicer indicates it's full. Immediately remove the battery from the charger.

Initial Discharge

Resurrecting a NiCd involves discharging it completely. Initially you turn on your cordless tool and then allow it to run until it stops operating. The tool will gradually get slower and slower, but don't turn it off until it stops working. Once the tool stops, turn it off and let the battery and tool cool. You will find they are fairly hot.

Secondary Discharge

Turn on your cordless tool; it starts operating again, but it won't have too much energy. Let it run until it stops as before. It probably won't take more than about 5 to 10 minutes. Turn off the tool and let it rest for a few minutes; 10 minutes is usually fine.

Deep Discharge

To resurrect your NiCd battery, perform a deep discharge. This drains all the energy from the battery and breaks up the cell structure, allowing it to retain a greater charge. Just turn on your cordless tool, let it run until it stops, then turn it off. Repeat until your tool doesn't operate. This means you have totally discharged your battery.


Put your battery on charge for an hour, possibly more. If your charger has a charge indicator light, leave your battery charging until either the light turns off or changes colour. Once your battery has charged, you can use at normal. In most cases your NiCd battery is resurrected, but repeat this process every six months or so, to keep your battery in good condition.

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About the Author

Stephen Benham has been writing since 1999. His current articles appear on various websites. Benham has worked as an insurance research writer for Axco Services, producing reports in many countries. He has been an underwriting member at Lloyd's of London and a director of three companies. Benham has a diploma in business studies from South Essex College, U.K.