I've been riding my ANCHEER folding electric bike to work for over a year and it's been working great. However, the past month, at time it stops working when going up slight hills. If I let it rest awhile, it will start backup. However, I live in rainy Oregon and need to get to work on time, so I have to get the problem fixed. My warranty has expired. I've tried communicating with ANCHEER, but am not getting any helpful information. I'm wondering if it's possible to replace the battery, and if so, if that may be the solution. Or does someone have another suggestion???