battery drain?
try disconnecting the alternator and see if the drain goes away.

There are only a couple wires at the starter, yellow and white, Yellow is wire from circuit breaker panel and white wire is from battery.
Then you would have the main battery cable and possibly a ground cable.

If you have a drain pulling the battery down then check and see if the alternator circuit may have a hung regulator or something else in the electrical system , best way to check is to run a battery drain test using a vom meter or test light. When running a battery drain test always make sure the battery is fully charged and in good condition.