After finding a pack of NiMH rechargeable cells that had never been used since buying them in 2014, [DiodeGoneWild] decided to test whether they could be tossed or not. After previously testing different brand cells that had gone high internal resistance after only about five years, he wasn’t expecting much. Amazingly, the batteries not only recovered, but seems to be not that much worse off for wear.

Three of the four precharged cells still held some voltage and happily charged back up to their rated 2,000 mAh capacity basically with the first cycle. One of them read 0V initially, but was revived using the typical manual charging approach involving a bench power supply. After a few charge-discharge cycles only the deep discharged cell showed some noticeable degradation with slightly reduced capacity, but all of them read healthy internal resistance values.

What this mostly shows is that not all NiMH cells are made the same, with the Tronic ones that previously failed after a few years doing much worse than these Activ Energy cells which are apparently sold primarily at Aldi stores. Overall NiMH is a pretty robust battery chemistry, so it’s always worth it to try reviving a cell before tossing it.