For the past few months, and seemingly getting progressively worse, I've had a charging problem: both battery and alternator test good (checked via charger with alternator test mode and higher-end test equipment at Advance Auto), but the battery doesn't charge. It doesn't drain when left sitting, but each time the engine is started, it gets harder and harder to start, until it won't start at all without a jump or push. Charging with the battery charger makes it work again for a while, but then it gradually gets harder to start.
Battery/charging system voltage seems reasonable, over 12V with engine off, and around 13.5V running.
Tested for any loads causing a drain just in case, but there don't seem to be any - battery charger drops to "float" mode and stays there after battery is charged.
Vehicle is 1992 Honda Civic.