over three year old battery. left uncharged in basement over winter. got new charger and seems to power up fine. after 3 miles of riding in high mode i go from the third light blinking to 1st light only blinking with sudden power loss to very low power( maybe a safe mode?). get home slowly and plug it in and voila, 3rd light is blinking as if it is almost fully charged... this repeats itself. have tried conditioning/levelling the battery. does not help. what do you think?