These are extremely cost effective power supplies / battery chargers. They can be used as a DC power supply with no batteries if desired. No special filters are required for radios and stereos. They operate at a wide range of input voltages and frequencies and still maintain full power output and constant voltage. Iota chargers automatically taper the charge current as batteries reach full charge. A manual jumper allows you to choose between 14.2 VDC charging and 13.4 VDC for float service. An optional IQ-4 adapter turns this unit into a smart, 3-stage charger. Solid state electronics and lightweight ferrite transformers are used to achieve a remarkable 86% charging efficiency. Iota chargers currently do not offer an equalization charge feature.