How to Repair Cordless Power Tools

But let’s say you have a cordless tool, and its battery is failing. Can you fix the battery? Of course you can. You are Hackaday readers, you’ll all be aware that inside almost all cordless tool batteries you’ll find a set of standard off-the-shelf cells wired together, C or D cells in the case of NiCd or NiMh Bosch power tool batteries, and maybe 18650 cells for LiIon. If you can defeat the efforts of your tool manufacturer to discourage battery pack dismantling, you can have them out on your bench, and replace them.

Of course, there is a snag to replacing cells in a pack. This isn’t like the spring-loaded battery compartment in your radio, each cell will have spot-welded metal strip conductors linking it to its neighbour, and you’ll have to come up with a way of replicating that. If you’re lucky you’ll find solderable batteries, otherwise you’ll have to consider a battery welder. But if you can overcome that hurdle, you should at least be able to replace your cells without breaking the bank.

You will be unlikely to find a tool with a NiCd battery for sale new these days, but there are still huge numbers of older ones with dead packs to be found often at next-to-no outlay. It’s not the safest of exploits, but it is possible to rejuvenate dead NiCd cells with the application of short bursts of high current. The theory goes that metal crystals grow in the cell and short it out, and the high current blows these metal crystals and brings the cell back to life. There are tales of this being performed with hefty bench power supplies, car batteries, and arc welders, though you may wish to research carefully before you give it a try.

Finally, who needs cells? If you have a suitably powerful low voltage supply, why not run your tool directly from it and forget about the battery pack? Of course, you lose the ability to run it as a cordless tool, but if it came to you at very little cost than that should present very little hardship. Try a modified PC power supply if it’s a 12 V tool, or a lead-acid pack if it isn’t.

So we’ve got past my rant about the iniquity of the built-in obsolescence of cordless power tools, and identified several ways that we as resourceful Hackaday readers can benefit from the cast-offs of others whose batteries have reached the end of their lives. It doesn’t change my personal view that I’d always still buy a tool with a cord by choice, but at least there are ways forward for those stuck with failing cordless tool battery. Do you share my feelings on this topic?

My battery pack had a thermister that aged, and was also susceptible to corrosion. It was unidentifiable by the time I saw it. If I knew what to replace it with, and had a strong confidence in not burning down my house or drill, I would rebuild it myself.

I’m not much into power tools, but I see the category is a huge opportunity for vendor lock-in and reduced tool quality (it’s battery-powered, so less sturdy, etc), and clearly some vendors have taken advantage.

Is the usefulness of battery tools that there is no cord, or that you’re independent of the grid?

It seems to me a good option would be a separate battery pack with an inverter, from which you could operate several corded tools. Aside from the cord issue, you’d have just one battery to charge rather than many, it would be separate from the tool, so would not affect handling, and could be larger and therefore higher capacity/power Dewalt cordless drill battery. it could be non-proprietary relative to the tools, and you’d be able to use more ‘standard’ corded tools.

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One Response to How to Repair Cordless Power Tools

  1. There is noticeably a bundle to understand about this. I suppose you made certain nice points in features also.

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