There are numerous correct ways to charge the batteries. Typically, charge at C/10 amperes, (where C = the 20 hour capacity of the system express in Ampere Hours) until the battery voltage rises to 2.583 Volts per cell (i.e. 7.75 volts for a 6V battery). Hold this voltage constant for 2 to 4 hours, and stop charging. A similar method would be to charge at the following upper limits and terminate the charge when the time limit is reached: Charge Current = C/10 Amperes Charge Voltage = 2.583 Volts per Cell Charge Time = 10 Hours Battery temperature adjustment: reduce the voltage by 0.028 Volts per Cell for every 10 degrees (F) above 80 degrees (F), increase by the same amount for temperatures below 80 degrees (F). Download the full detailed charging instructions