Alternator Squeal on startup with tiny battery
 

Last year when I built the car I put in a tiny 16-cell EVO2 battery (~3 pounds). It cranks the car great, even after a month of not starting it. However, after every startup, I get crazy belt squeal on the alternator proportional to how long it'd been since startup. I've tried adjusting the belt both tighter and looser, which has absolutely no effect on the squeal. I've had the alternator rebuilt and it also had no effect.

My best guess is that the battery has such low internal resistance that it actually overloads the alternator at startup until it charges back up to full from the startup cranking.

The motor is a 99 but it's in a 91 car, and I'm just using a 94 alternator so I don't have to deal with the variable voltage regulator.

Anyone else had this phenomenon and/or have any ideas?

It's mostly just really annoying, since it sounds like a wailing banshee for like 30 seconds on a cold morning startup, which isn't ideal at sites where we're supposed to be vaguely quiet. :)

Have you tried just replacing the belt itself? Could just be worn out.

Im trying to remember if we can full field our alternators. If we can, you could start it up and full field it. That will verify your hypothesis on it working extra hard after cranking

Yeah, shouldn't mentioned that. I've tried several different belts as well. :(

I'm wondering if switching to an NB variable-regulated alternator would help at all. The Hydra can control it, and it might let it open up some more.

If it's any help, I'm running a MS3 and I had startup squeal issues after installing the MS. I ended up having to tighen the belt more (more than I though it needed) but still safe.

04 MSM

I don’t know if the 2.7 hydra is any better but I know numerous people have given up trying to get hydra to consistently control the alternator and just swapped to an earlier internal regulated alternator.

I put a bigger diameter underdrive pulley on mine. more mechanical advantage but I don't think it makes full charge voltage until about 1500 rpm. just enough to keep the battery charged fully at idle at around 13 volts goes up over 14 with a few more rpm.