Hi,
My '90 civic seems to drain battery quite quickly. It was out of power
this morning (after 4 days of not use). I could jump start it without
any problem. After running the car for a while, I shut off the enginee
and restarted the car, no problem. But after a couple of hours or so,
the battery seems getting quite low, to a point that it just barely
started the car after a few trials.

The battery is probably more than 5 years old (diehard). I think it is
time to replace the battery. But could it be the alternator or
something else? I am pretty novice on cars.

Any suggestions for me to test it further before taking it to a shop?

Thanks.

Tony