I assume a lead acid battery. You certainly should have told us everything about the battery, with the question. In a lead acid battery, state of charge is indicated by electrolyte density, measured by hydrometer. Same hydrometer reading in all cells is important. If you have access to inter-cell terminals, then you may balance state of charge, of the individual cells. If you don't have terminal access, then a mild overcharge of the whole battery may improve balance somewhat.
If we are talking about a lithium ion battery, DO NOT OVERCHARGE, EVER!!