If the batteries are low, the 4410A or APM-16 will still function but the accuracy of the readings may be affected. Check the condition of the battery occasionally with the battery test position on the range switch. If the pointer on the meter indicates a weak battery, the battery must be replaced (4410A and APM-16) or recharged (4412A).
Models 4410A and APM-16 use one 9V alkaline battery. The 4412A uses one 9V NiMH rechargeable battery or an AC converter.