Customized 18650 lithium ion battery pack 2s battery 7.4 8.4 volt battery 3s battery 11.1v 12v battery 4s battery 14.8v 16v battery 5s battery 18.5v 21v battery 6s battery 25.2v 22.2v battery 10A battery 5a battery 3c battery 5c battery 3s2p battery