My 2001 Elantra still has the original battery. I have only 40K miles on it, regular servcing as per the manual. The only time it failed to start was after being in the airport parking lot for three weeks, the battery needed a boost. This morning the power door locks did not operate but the car started and we drove away. For the rest of the day the car door locks operated normally, locking and unlocking under power. My question is whether this is a sign the battery is on the blink.