Boge, I do a lot of work with the 12v, 7Ah sealed lead-acid battery. Fully charged I expect it to read anywhere from 13 to 13.5 VDC open-circuit voltage. A light load might drop it to 12.5-->12.8 V, a moderate load down to maybe 12.2-->12.3; and it takes a heavy load indeed to start out at less...