Designed around the needs of the battery specialist, fleet operators, warehouses, and reclaimers. The constant current output is current limited, and is controlled by one linear adjustment. Voltage is adjusted automatically on the QPA6-127v/6A, and a range switch is used on the other two models. These models use no micro processor, and are ideal for busting loose stubborn sulfation using a slow 12-24 hour charge. The reverse polarity feature, and isolated, all copper transformer make the Series Multi's safe.