Battery voltage drop while driving
 

I've searched but not found anyone with this exact problem. I'm running a MS2 Enhanced from Reverant. There have been a few issues lately that I'm working through, today went out for a drive and did some data logging. One thing I noted during the drive is that initially I was seeing 14.0-14.2 battery voltage. As soon as the coolant temperature reached 152 degrees F the voltage dropped to 11.5 (that may or may not be related). After my initial data log I stopped the car twice, then turned logging on for my trip home. The battery voltage was at 11.5 initially for that log then dropped over time to 11.1.

Due to some other weirdness I have had over the past year or so (battery only lasted a year, car died with no apparent cause then restarted after about 20 minutes with no problem) I am guessing my alternator might be shot. I had it checked at a place that rebuilds them back in January and they gave it a clean bill of health, but I'm thinking it might be a heat related open of some kind. Any thoughts?

Year?

Sorry, 2000. I'm running a BRP MP62 intercooled supercharger setup as well.

Does the MS2 enhanced use the Westfield alternator control circuit? Is the alternator voltage shift vs clt repeatable? If you load a tune from before you fixed your issues, does it still have the same problem?

Thanks for your response.

Don't know about the alternator control circuit, from what I know mine dates back to when Reverant was doing his own control circuit. Didn't try to repeat the voltage shift vs CLT as I would like to figure this out before I damage anything. Issues I mentioned aren't fixed as yet, didn't try loading a previous tune though. I'll give that a shot when the weather clears so I have one less thing to deal with while troubleshooting this.

You may want to reach out to Rev, as he does his own custom FW. The NB alternators are controlled by the ECU.

11.x V sounds like you are running completely off of the battery. You should have a battery light on the dash when this is happening.

Might be worth getting the alternator tested again.

Battery voltage drop while driving reasons and fix complete guide. Read Here

Check your main power wire at the alternator. Found mine was partially melted due to heat/current. My car would randomly drop to 12v and be super lean/cutting out. Turns out the eyelet at the alternator had gone bad.

Adding better fans, fuel pump etc really loads up the system compared to the factory components. More than the alternator can handle. FWIW I switched to an RX7 alternator and am going to run a new power wire. I did a temp fix on the eyelet for it and my voltage hasn't dropped below 13.7 since.