2s bms 8A 7.4 volt 8.4 volt bms 2s 18650 2s bms charger bms 2s 6v bms2s Charge Protection circuit Board micro JST connector jst xh 2.54 3 pin connector BMS for 18650 Lithium ion Cells BMS Li-ion Lithium Battery 7.4v 8.4V 18650 Charger Pakistan E shop