Lead-acid replacement batteries from A123 Systems.
Ultra Sports Starts packs come in two different case formats, both with built-in protection circuit modules. The standard black case, typical of lead-acid batteries and also a clear case. The clear case is slightly heavier than the lead-acid case.
The 4.6Ah packs offer up to 60Wh whereas the 6.9Ah packs offer up to 91Wh.