Lead acid batteries should NOT be charged by a constant current charger as suggested by some. Instead they should be charged using a constant voltage source that is preferably current limited to reduce initial charging current. The voltage should be set to approx 2.30-2.35 V/cell and the initial current limit to somewhere between 10 to 30% of the stated capacity. For a 12V, 7Ah battery a voltage of 13.8-14.1V and a maximum initial current of 0.7 to 2.1 A. is about right. As the battery is charged the current will decrease automatically to approx. 3-4% of the rated capacity, i.e., 0.21-0.28A for a 7Ah battery. When this happens the battery can be considered fully charged.