ETC recommends using rechargeable batteries. As with any rechargeable battery, these provide the best source of power and longest operating life when allowed to be fully discharged and then fully charged. Most users simply use the RFR and then plug it back into the recharger when done - not allowing for the batteries to fully discharge. This type of use will limit the life of the batteries to 3 - 6 months. Best practice is to either have two sets of batteries and a charging system that first discharges then fully charges the batteries each time they are plugged in (keeping one set in the charger and another in the RFR) or to use the RFR until fully discharged and then fully recharge before the next use.