Hi, I'm Leonard and looking to rebuild my 24v 12Ah UM36 battery. I've tried to purchase a new core from UM website but it won't accept payment. Having checked out old Pedelec posts I can see that their heyday was 2010 and since then there is no UK phone contact. I've posted two webforms to them but no reply. I can rebuild the battery if I can find a bona fide Li-Ion core with BMS card built in. There are many on internet but when I check the individual reviews, it woukld take a stronger will than mine to order from a company with 43% negative sales comments. Ive tried the bike shop in York but they dont do 24v any more. Does anyone know if it's possible to upgrade the bike to 36v without having to change everything? Any advice will be appreciated....