Rep Power: 511

So, on the way home, my car started having a voltage issue.

Symptoms and other info
-Voltage being maintained between 11.2-11.6 volts. This morning, voltage was being maintained at 12.8-14.6, which was normal from before. I did post an issue about my voltage dipping into the mid-12's, but gearbox said it was the ELD doing it's thing.
-Battery light comes on when RPMs dip below 1700, and clears when RPMs rise above 2300.
-When I noticed the problem, I shut my sound system off, no change in symptoms.
-Alternator belt in tact. Old (still have original belt after 124k miles), but in tact. I know, I need to replace my timing belt and accessory belts..
-ELD replaced 11k miles ago.
-Battery (optima yellow top size 51) is old as ****.. January '05, if I remember correctly. If not January, early '05 for sure.

Any ideas? Figured I'd ask the forums before replacing ****. And no, I haven't gone to autozone to get my battery/alternator checked yet.

Video was a drive around the block. VAFC-II (only there for extra instrument reading now, not hooked up to any vtec or a/f control) and cigarette lighter voltage metering. I apologize for the shakiness.. It's kinda hard to hold an iPhone while driving a stick/taking video.. lol
[youtube]http://www.youtube.com/watch?v=Txp0njRKNHo[/youtube]

 
Rep Power: 811

get rid of that yellowtop, its junk. but aside from that, sounds like bad alternator if voltage dips below 12v. thats the battery trying (and failing) to keep the car running. if the battery light comes on, esp in lower rpms, the alt is not making enough power.

 
Rep Power: 511

any battery recommendations? I've had it since 05 and haven't had any problems with it

 
Rep Power: 291

def have the alt checked out...

Batt shud never go below ~12.3 volts

Get ready for your shitstorm

 
Rep Power: 811

honda battery group51 with 500cca is a good choice (made by interstate). i am a big fan of maintenance type lead-acid batteries so you can just pop open the caps and add distilled water to keep them happy.

 
Rep Power: 291

I really like the ACDelco batteries, got one in mine atm

 
Rep Power: 511

edit: bah.. no alternator on the spare engine.. anyways, are dayco or duralast belts any good? or should I just go to the dealership and grab one?

 
Rep Power: 811

most belts are pretty good for accessories, and you can always change it if something happens. im still on my original bando belt for the PS for about 6 yrs.

 
Rep Power: 511

A few hours of disassembly, hunting down misc bolts and parts (new alternator, an I figured new ps/alt belt while I was in there) and reassembly, and she's breathing happy again. Charged the battery overnight (tested fine last night @ autozone), started her up, VAFC-II read 14.6V and steady.

Thanks for the input. I figured it had to be either battery or alternator, figured I'd ask the forum anyways.