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I feel like my battery gets low quickly and the battery is only a few months old. If I don’t drive the car for a couple days the voltmeter is at 15-15.2 all the time. No aftermarket electronics or anything.
What year is your car? Did you see these same readings in the warm summer months?
15V sounds very high. Are you seeing that with the car off or while running?
DaveGee
Only while running. I was seeing this on the original battery too, then I replaced with with a new, correct spec battery from Costco, reset the BMS system, and get the same voltages after a couple days off the tender.
The only time I don't see this is when the car is fresh off the battery tender.
I remember this topic from years ago and someone saying that leaving the car unlocked is in fact a massive drain on the battery because it puts all the electronics in "here we go" mode and ready to activate when you jump in to your unlocked car, as opposed to being asleep in a locked car.
Someone would have to prove that to me or show me some documentation on the subject.
My car seems to go asleep pretty quickly once turned off and doors are closed and reawakens when you open the doors.
But unfortunately my car is currently asleep plugged into a battery tender at home while I'm working a project away from home.
Someone would have to prove that to me or show me some documentation on the subject.
For example, page #19 of the Owner's Manual:
"Operational readiness of Porsche Enter & Drive is switched off after 96 hours for the driver's door and after 36 hours for the passenger door..........."
This was also very common and well known on the 996 and 997. After about 5 days of inactivity, you needed to open the driver's door with the blade key, and cycle the ignition within a set time, to re-awake the car.
Only while running. I was seeing this on the original battery too, then I replaced with with a new, correct spec battery from Costco, reset the BMS system, and get the same voltages after a couple days off the tender.
The only time I don't see this is when the car is fresh off the battery tender.
Hmmm, I was under the impression that a “normal” range while running was around 13.4V Hopefully someone with better knowledge on the subject will chime in.
Hmmm, I was under the impression that a “normal” range while running was around 13.4V Hopefully someone with better knowledge on the subject will chime in.
DaveGee
Originally Posted by Antigravity
It will range from about 13.5 to 14.8 in gereral, but note, in the Winter months it will go up higher as the ECM will modify the Charging profile to compensate for the fact that in cold weather Lead/Acid takes a higher voltage to charge because it does not accept a charge as easily as when it is warmer. We have seen some some Porsches go into the mid 15v range which is considered too high for an AGM in general during charging, but we've seen it and that is how Porsche does it. Most other Cars usually stay below 15v even in winter. But as I said we've seen it, and mostly only in Porsches so that just how they do it. I'm talking 911 for the most part.. but I assume it roughly the sames in the 981s.
We know this because we tested in tons of Cars with this device we make called the Battery Tracker. If give a voltage reading for the Battery for 31 prior days and sends the data to your phone. Below is an example of one day showing a 24-hour profile of the battery that is on your App on your phone... It shows I drove the car starting around 2:30 in the afternoon... drove for about 45 mins where the voltage was in the 14s, then stopped for about 30 mins (probably to get something to eat), then drove again and turned off the car 4pm. I can also see with that redline that the voltage was 14.76v at 3:49pm (military time shows as 15:49) If you slide you finger back and forth you can see the voltage at any time in the graph.
Yesterday I unplugged the GTS and did a gas/Lowes/Dunkin' run. Took the LONG way around. Did wonders for my morale. Returning home I hooked her up to the Battery Tender again. Maybe I'll do it again in a couple of days - I think I'll "need" toilet paper by then.
I usually keep my 2017 Base Cabrio connected when I don't drive it for at least 3 - 4 days. If I don't connect the car and I don't drive it for at least 2 weeks, when I connect the battery charger immediately goes into "save" mode, which means that the battery has been draining even if not used. These cars should come with a charger included in the base equipment of the car...... it is mandatory to have one if you don't drive often.
For me ? Peace of mind that the connection always work and I don't have to worry about the outlet going to sleep. Not saying that the outlet is a bad alternative..... just the direct connection once installed, it's a better solution for me.
03-31-2020, 11:22 AM
Returning home I hooked her up to the Battery Tender again. Maybe I'll do it again in a couple of days - I think I'll "need" toilet paper by then. 
