NiMH cells – A set of NiMH rechargeable cells bought in 2014 and left unused for 12 years showed surprising recovery: three cells held voltage and charged back to rated 2,000 mAh capacity, while the fully drained one was revived with a bench power supply.
When a battery pack’s labels fade, you don’t think “miracle.” You think “expired.”
That’s exactly the mood behind a recent test after a bundle of NiMH rechargeable cells — bought in 2014 — sat untouched for 12 years. The experiment started with a simple question: could the cells be tossed, or was there still life in them?
The person running the test previously tried other NiMH brands that developed high internal resistance after about five years. With that experience in mind, he didn’t expect much from these. Still, the results were striking.
Out of four precharged cells, three still had some voltage after the long dormancy. They then charged back up to their rated 2,000 mAh capacity basically with the first cycle. The fourth cell initially read 0V. It didn’t stay dead, though. It was revived using a manual charging method powered by a bench power supply.
After a few charge–discharge cycles, only that deeply discharged cell showed noticeable degradation — with slightly reduced capacity. But even then, the measurements came back with healthy internal resistance values across the board, suggesting the chemistry hadn’t fallen apart.
What stands out isn’t just that the cells worked again. It’s that not all NiMH cells age the same way. The earlier brand cells that failed after only a few years did worse. with high internal resistance showing up much sooner. By contrast. the tested pair of brands behaved differently: the Tronic cells reportedly performed poorly. while the Activ Energy cells — sold primarily at Aldi stores — were the ones that recovered and held up far better after years of sitting.
Taken together, the experiment lands on a practical message for anyone staring at an old rechargeable pack: NiMH is generally a pretty robust chemistry, and it can be worth trying to revive a cell before writing it off.
NiMH rechargeable batteries battery revival internal resistance 2014 battery test 2000 mAh Aldi Activ Energy Tronic batteries
So you’re telling me my dead batteries might not be dead? I’m gonna go dig around in the junk drawer.
I’m skeptical lol. If they can revive after 12 years then why does my charger take forever and the batteries die in like a month? Sounds like selective testing.
Wait so one cell was at 0V and it still came back… but wouldn’t that mean it’s dangerous to charge? Like you can revive anything if you have the right bench power supply.
This is kinda wild, I always thought rechargeable stuff just “expires” after a few years. Also the Aldi one mattered?? I’ve bought those cheap Tronic/whatever brands and they felt weak anyway, so idk. But if internal resistance stays healthy then it’s not really age-related, it’s more like storage and how it was used? Or maybe they just got lucky with the batch. Still, I’m not trusting 12-year-old batteries in my smoke detector or whatever.