I just purchased this bike. At first the battery was a little weak. When putting into reverse, it would just bump backwords one time when I pushed the button. I checked the battery. Had to fill it and charge it. Now the bike turns over allot faster when starting. Now when engaging reverse, it will bump backwords each time I hit the button. But will not stay engaged. I read somewhere that low voltage can cause this. Could this still be the case even though the battery seems to be stronger? Any help would be greatly appreciated.