Battery and alternator charging question.

Hello. I suspect my alternator is not charging my battery. I haven't used this car since April of this year so the battery had run down to 2 V (I measured it with a volt meter). The battery had been connected to the car.

I got it charged about a week ago at a car repair place. When I got it back, I measured the battery voltage with my voltmeter to be 12.75 V (with the engine not running).

I haven't used it all that much since then (few trips around town) but now the battery voltage is about 12.25 V (with the car not running). When I test the voltage with the engine running, it's slightly less than when it's not running. Shouldn't it be more since the alternator is sending it
current?

What I want to do is get an ammeter and hook up the ammeter between the cable from the alternator to the positive post on the battery. Then get the car running and see if any current is flowing from the alternator to the battery. The question I have is what should be the current (roughly speaking) flowing from the alternator to the battery?

Are there any easy tests that will tell me if the alternator rather than the battery is faulty (or vice-versa) such as turning on the lights when the engine is running? If the lights dim when the engine is running, does that automatically mean the alternator is not charging? Could the problem be the battery's not holding the charge that the alternator is sending it?

Thank you for any help in answering any of the questions I posed! Take care,



No ammeter necessary. If your battery voltage is less with the car running than it is with the car not running, your alternator isn't charging your battery. That doesn't always mean the alternator is defective (you could have a wire loose or something somewhere) but it does mean your charging system isn't working and needs to be repaired if you plan to drive the car for any length of time.