I just ordered a BL-36 kit. The kit comes with three 12V 12Ah sealed lead acid batteries connected in series. I'm not 100% sure if the controller can handle 48V. However, assuming it does, does anyone have any information on whether you could use a 4th 12V SLA battery in series with these batteries. The catch is the 4th SLA battery will be a 2Ah smaller SLA battery than the other three. The intention is that I would be able to have a little extra juice, given for a short time. So my question is whether anyone knows if this setup could potentially cause a problem given the different Ah rating of the 4th battery? Thanks for any input. By the way this will be my first ebike setup, and I am intending on putting this setup on a cheap 26" Huffy 18 speed bike from Walmart.