Energizer makes some 2100 mAh AA batteries. I think the key is not to overcharge the batteries. If a charger takes a very long time to charge (like 8-14 hours) then it is possible it is a trickle charger and if the designer is not careful, these can overcharge the battery if the batteries are left on to charge for too long. NiMH batteries supposedly don't have any memory effect, so completely discharging is not required. However, some chargers (like the one that comes with the Hotronic warmers) charge at a rate slightly above trickle for a certain time (~10 hours), then switch to a very low trickle charge. Since this is a timed charge, they recommend discharging the batteries so that a battery that is only 20% discharged (for example) won't get charged for the same length of time as a fully discharged battery. So basically they recommend discharging just to get the battery in a known state of discharge. Good (ie more expensive) chargers charge at the rate of "1C" (which for a 2100mAh battery would be around 2.1 amps) and then it only takes a little more than 1 hour to charge the battery. But doing this requires a charger that is a smart charger (one that makes decision to reduce charge rate based on increased rate of temperature increase in the battery, or a drop in the voltage: -dV/dt) and is capable of sourcing larger currents.