Engine Battery light!

Battery light!

I have a 2000 Corolla CE, 1zzfe vvt-i motor. Yesturday I was driving around, and all of a sudden my Battery light came on, my clock went out, then my radio, then my gauges got dim, I just barley made home, pulled in the driveway, and turned it off, tried to start it again, and it tried to turn over, but seemed like the battery was drained. I put a volt meter on the battery and it was at like 10.5v.

I bought a new Red top optima today, took it home and installed it, drove to Advanced auto parts, and they "tested" the alternator, and siad it was fine. left there drove 2 blocks and the battery light came on again. came right home, put a voltmeter on it, it's at 11.5-12.3 running, and around 11.9-12.9 off.

Now my car did sit for about 5 months while it was in the body shop, and my buddy put a battery tender on it for a while and even disconnected it for a while to keep the alarm from draining it.

Now is there any thing I can do to test the alternator to see if it's bad? besides unbolting it and taking it back to Advanced auto to have them bench test it.

Im looking in to getting a HO alternator at the end of the month, but wanted to know if there was any thing I can do to make my alternator last?
Thanks

check out your belt tensioner cause your belt might be slipping through the Alt or go to Auto Zone and they can test your Alternator on the car for free while it is running .....DUH..... By the way they test batteries too WHILE ON THE CAR .....DUH....They have a Starter test to ......AND LOOK YOU DONT HAVE TO TAKE IT OFF YOUR CAR.....DUH......

I did have my old battery tested and it was toast, I bought a brand new Red top Optima, put it in and drove back to Advanced and had them test my alternator, they said it passed, left, drove 2 blocks and the Battery light came on again, and cant get it to turn off. now battery is reading around 11.5-12.3. From what I can find on the web reguarding toyotas and the battery light, it looks im gonna have to replace the alternator, which I was planning on anyway. Just wanted to know if I missed something to check, or a way to extend my alternator for a few weeks.

Check the wiring to the alternator. Some wire could be frayed.

it also depends on what kind of tester they are using.... if they're using an old tester that really only checks for voltage then it might be missing something (ie the diodes going bad.... causing the regulator to act funny)

if I were you, I would just pull it off and have it checked..... because when they check the "alternator" on the car they aren't checking the alternator.... they are merely checking to see if "charging" voltage is reaching the battery..... if it isn't then the idiot that works there will probably say "you have a bad alternator"... when (depending no the car) it could be a regulator (if external, in your case no), a bad battery causing the alternator to act funny, or a multitude of wiring issues......