A. No, we do not recommend using your existing LEAD ACID/GEL Battery Charger for your new SUMATOTEK Lithium-Ion Battery / Ferro Phosphate Battery. Even if the upper cutoff voltage is the same, LEAD ACID/GEL Batteries use Constant Voltage Charging Methods while Lithium-Ion Battery Chargers use Constant Voltage and Constant Current Methods to charge the battery. Simply put, one can say that when the Lithium Battery Voltage is low, Lithium Charger lowers its voltage while delivering constant current and as battery voltage reaches within 90% of its upper cutoff voltage, the Lithium Charger decreases its current while keeping the voltage constant. however, this doesn’t happen with the LEAD ACID/GEL Battery Chargers. The LEAD-ACID/GEL Battery Charger can charge the Lithium Battery but it will hamper the No. of Cycles of the Lithium Battery. It might also pose a fire hazard in case of overcharging since low-cost LEAD ACID/ GEL Battery Chargers are quite popular and do not have strict upper cutoffs, which is very important for Lithium Batteries. Lithium Batteries tend to heat up or cause fire hazards if the cell voltage exceeds its maximum ratings even by a few millivolts.