NiMH battery pack charging


I purchased two of you 7.2 V 700 mAh battery packs (item# 1008) and I have a charging question. I use a Hobbico Accu-Cycle Elite charger for all my battery charging needs and everything has always gone great. However, while charging the pack this morning I noticed the battery pack was really hot and mAh was 800+. So, I am wondering if I need some new parameters. I was using the following and it happened on the 2nd of 3 cycles…

Type: NiCd/MH
Number NiCd/MH: 6 (7.2V)

NiCd/MH rated: 700mAh
NiCd/MH peak chg: 0.30A
NiCd/MH trickle: 20mA
Peak sensitivity: 8mV/cell

NiCd/MH dischg: 0.3A
NiCd/MH dsch cut: 1.1V/cell

NiCd/MH cycling charge: 0.3A
NiCd/MH cycling discharge: 0.3A
NiCd/MH dsch cut: 1.1V/cell
Number of cycles: 1


I charged the second pack last night and it was past 900mAh before I manually stopped the charge. This pack was very hot as well. I have used this charger for years on AA based packs and I have never had this issue. They never get more than warm and they never go well beyond their mAh ratings. Is this normal for NiMH? The typical packs I have charged in the past ar NiCd, 4C, 800mAh.

Finally, I would appreciate some help from the Pololu staff as these battery packs are brand new and I don’t want to see them get damaged or explode.

Thank you,


I’m not familiar with your charger, but most of the ones I have seen have different settings for NiMH and NiCd packs. I’m not sure what the peak sensitivity parameter means, but perhaps that’s something you need to adjust differently for NiMH cells. Also, is there a total mAh or time limit you can put in? I’ve also charged ours at 700 mA with decent results, so you might try that. At least you’ll know within about an hour or so if the peak voltage is getting detected, as opposed to waiting a few hours at the lower charge rate. At the higher charge rate, it will be more important for you to keep an eye on things since the pack could heat up more quickly.

- Jan