Whats going on!!!

My 1991 Civic HB DX has been running pretty good with no problems. One day I start the car and I'm driving the car and the battery light turns on. I get worried because I'm on the highway. Anyways I went home and tested the battery and it was fine. I even took it to test the battery at the store. It was fine as well. So the guy said it could be the alternator but that wouldn't make sense because the car starts with no problem every time I turn it on. That light keeps coming on now and I have no clue WHY!!!! What do you think??? Could it be a short circuit or some kind of relay? Please help. Thanks in advance.

It's probably the alternator.

It's probably the alternator.

I agree. Your car may start fine now but if you listen to your stereo and use your A/C or headlights then try to start your car later it may not happen. Have your alternator tested and check your grounds.

light came on b/c it's a warning light...don't want it to come on when your car breaks down...but light they said above...get the alternator tested

your alternator could be putting out too much voltage. i dunno if the car's sensor is that intelligent or not, but i've had a voltage regulator go out on my old nissan pickup, and it began to slowly fry the battery. i smelled the burning battery for weeks before i finally noticed headlights getting super bright the faster i drove. changed it as soon as i found out. battery didn't last much longer than that either due to being fried.