LiFePo4 + dummy is the best solution when there are 2 AA-batteries in series. Mostly because of 10000 charge cycles instead 500 of NiMH. Capacity is about %70

LiFePo4 + dummy is the best solution when there are 2 AA-batteries in series. Mostly because of 10000 charge cycles instead 500 of NiMH. Capacity is about %70, when we compare the bestest batteries. --- Correccion: LiFePo4 is better, but good batteries are very expensive. Also flat voltage curve extends usable capacity. Only problem is that when LiFePo4 is totally emptied it easily dies and so protected version may be worth the price.