So your gonna want to test the alternator and battery, but let me drop an anecdote here.
I had intermittent charging issues on my accord last year.
Car would run fine, but often would need a jump in the morning because the battery was flat.
I started by cleaning the battery contacts with cleaner and wire brush.
Problem persisted.
Had the battery replaced because it was under warranty.
Problem persisted.
Replaced the alternator and serpentine belt because the battery wasn't charging.
Problem persisted.
Finally, I bought some heavy duty battery post clamps from auto part store. I sliced off the Honda clamp and spliced the new clamps on.
Problem fixed, never had another issue.
Good luck
