I have a trike which I purchased with a 250w motor. Last year I bought a 1000w kit and upgraded. The controller is 36v/ 48v and for nearly a year I used the 36v 15 ah battery, that came with the original bike, without issue. I have recently bought 2 36v 25ah batteries hoping to get a little more range. One of the batteries is fine, the other however fuses if I go up a hill. I have spoken with the vendor who tells me I need a bigger battery., but one works absolutely fine. Am I being fobbed off?