Power tool battery charge

They separate mains voltage area and output part area in my opinion.

I've seen some chargers that wouldn't even try to charge a zero-volt battery. It's almost as if some of their circuits are powered by the battery being charged. Open circuit, the charger's output is zero. Strange.

The fix is to partially charge the battery with a bench supply to bootstrap the process.

I opened up the battery cases, to find a circuit board of a level of complexity that wouldn't be amiss in a smart phone.

It eventually occurred to me the check the voltages across the lithium ion cells. Each battery had a number of cells showing 3.6V, and one showing 0.7V. The one showing 0.7V was in a different relative position in each case. One battery also had a cell showing 2.4V. So it looks like both batteries really have failed, and the charger is probably OK.

I'd swap out the cells, to make one good battery, but they've been spot-welded in series.

I got about 3 years 6 months life out of them. I'm just a bit suspicious that the warranty was for 3 years.

Sylvia.

Try this trick for reviving the cell first: DIY: How to revive a dead 18650 (or any) Li-ion battery cell (4:36)

Crude spot welder for battery pads: (4:01) I use a 12V 20AH AGM battery, relay, push button, and an eBay timer. However, I use two copper electrodes and no "ground" clamp to the LiIon cell. Like this: DIY Battery Spot Welder - Update & Demonstration (23:46)

There is probably a warranty timer built into the battery packs.

Also, if your cells have a CID reset (short circuit protection), you can reset it using one of these methods: Do this only if the battery shows 0.00V, not 0.7V.

Try trickle charging the low volt cell... 5V with series resistor will do.. 100mA ?

That's what I was suspicious of. Clearly it wouldn't be difficult to design such a thing into a device that has its own power supply. Though I think if a company in Australia did this, and they got caught out, they'd be in serious trouble (Ozito is a brand name for one of the big hardware store chains here).

It doesn't look to me as if there's any provision for charge equalisation, and by the same token, I don't see how the circuit could intentionally kill one cell, or just fail to charge it.

Sylvia.

YOu can cut the tabs and solder the tabs together with a short piece of wire. Just don't let any heat get to the cell. Problem is that it will make the cell too long to fit back in the case. Another issue is that the charge controller will notice that you've disconnected the power and take a dirt nap. I never found any way to reset a lithium charge controller chip after replacing one or more cells. It's surely possible, cuz they have to do it at the factory, but it's secret info.

Often does work with NiCd...but not lithium.

Better to use a bench power supply with the voltage set to