In an exemplary fast charging system, a hand-held computerized terminal with rechargeable batteries therein may be bodily inserted into a charger receptacle. The terminal may have volatile memory and other components requiring load current during charging. The system may automatically identify battery type and automatically adjust to different levels of load current. The battery temperature may be brought into a relationship to surrounding temperature such that by applying a suitable overcharge current value and observing any resultant temperature increase, the level of remaining battery charge can be determined. For example, if the battery is found to be relatively fully discharged, a relatively high fast-charge rate may be safely applied while monitoring battery temperature. If the battery is initially relatively fully charged or reaches such a state during fast charge, the system may automatically dynamically select a maintenance charge rate according to battery type and temperature. A preferred system may automatically recharge the batteries of a portable device according to an optimum schedule of essentially maximum safe charging rates as a function of battery temperature, and thereafter safely maintain the batteries at essentially fully charged condition in readiness for maximum duration portable operation.