You can build and use custom battery with Yamaha system, or you can purchase an aftermarket battery for Yamaha, or you can rebuild the original Yamaha battery with new cells and new BMS, it was hacked.Once that battery is gone, its probably gone forever. This is the reason I am staying completely away from any bike with a slick in-built proprietary battery. When the battery goes the bike is junk. Probably not even sellable. We already see this happening with ebikes whose manufacturers have gone belly up.