I've had a similar experience with NiMh packs - the 'fancy' charger will false peak, and shut off way too soon. A cheapo Hobbico 'Fast Field Charger' seems to do OK- but the overnight wall-wart type charger is probably best. Especially with a new NiMh pack, expect to cycle it 4 - 6 times before it comes up to capacity. It may require manually charging with one device, then discharging on another. A good LiFe pack is a lot less hassle, IMHO.