| Sounds like it's not charging for a start, so the usual - charging fuse could be blown/dirty/corroded or the reg/rec is knackered (you should get around 14.5 volts across the battery terminals when the engine is running - some say around 3K revs but I get that even at idle).
Assuming all you contacts are tight, there is nothing to say that they might not be dirty/corroded and are arcing. It might not be the positive battery terminal either, I reckon it's more likely to be the starter solenoid arcing...again regular suspect for the dirty and corroded arcing syndrome.
If all you charging circuit checks out OK (including a check for burnt connectors and blackened wires) it could just be that the battery is knackered and isn't holding it's charge |