Progressive Dynamics - max current before overload

Of course that is true about a charging source having to be higher than the batteries open circuit voltage. I think if you have 400 amp hours or more worth of heavily discharged batteries sitting at say 11 volts, even if the charging voltage is 11.5v a mere half volt above the batteries, that might still cause a fair amount of current to flow. Obviously this might only be for a few minutes, and then the charger will have to constantly raise voltage.