JimEb

Took my car for the first drive of the season. Ran in normal mode the whole time (30 minute drive) and the voltage was 15.1V the whole time.

In Sport Plus mode the voltages usual get in the 14’s. First time I ever saw it this high. I did have a battery tender that let the battery go dead over winter. Replaced that about a month ago. Wonder if maybe the battery was just still really depleted? Car started fine. Battery is <1 yr, 900CCA AGM.

I don’t know how these alternators work to vary the output. Don’t see any mention of a voltage regulator in the FSM so I assume it’s built into the alternator? I’d think if the alternator went supernova on me the car would pop a warning or something. Putting a new alternator in isn’t a big deal, but don’t want to just fire off the part’s cannon full of guesses.

Southbranch

Sounds normal. The charging system takes a number of factors into consideration including the ambient air temperature. In cold weather, it charges at a higher rate. Mine was at 15.3 V today with air temp in the low 50s F. Also, your battery probably was somewhat discharged. I wouldn't worry about it.

asellus

Totally normal, these threads come up every year when people drive in the cold for the first time in a while.

There's an AGM float/charge voltage chart by temperature around somewhere...

IXLR8

My MFD voltage reading falls right into the chart, 14.8V @ 6°C.

Depends on the temperature. Worth dowloading the chart and sticking it in your Automotive folder. I also have one for GEL batteries if you are running trolling motors.

Source: East Penn Battery (manufacturers).

Pavegeno928

2014 991 with 95K miles and volts run high 14s/low 15s in SportPlus and one volt lower in normal mode. All is ok.

JimEb

Thanks everyone.

Sometimes having that gauge on your dash just gives you another source of anxiety. Was even stressing about how fast the car got up to temp. But it stabilized right at 192ish. That first drive after a long winter storage makes you a little nervous.

asellus

mmm, yeah... about that...

https://rennlist.com/forums/991/1283...t-the-fix.html

Southbranch

Well, he probably meant 194 . . . .

asellus

had to have