Bought my BBS02 with 17.5 AH batt abt two years ago. Works great except.... it seems to have a bit less power going up hills than during the first summer. First summer it was zooming up 10% grades. This summer it is struggling with a steep grade. I haven't put a lot of hours on it, and I am not an experienced bike mechanic. Is there a simple way to troubleshoot this WITHOUT taking controllers apart, etc.