[KobraKarl]

Zderf,

Take your battery (after you have fully charged it ) to your local NAPA or B&B and they will "load test " it for you. Your volt meter may read 12 or 13 sitting ,but under load an old battery will drop to 7 or 8.......your symptoms are typical for a battery getting ready to expire.

The " shade tree " test for a voltage leak is to pull off your positive terminal connector , shut off the garage light and just barely touch the connector to the terminal ,look for a miniscule blue spark.

Good luck KK