Possible Battery change - high charging voltage
02-21-2018, 09:56 PM
#31
Rennlist Member
By the way, did anyone ever answer the original question? I guess GregD indicated he is not sure that maintaining the power did much but he only had to reset the windows. But the bigger issue, what about the dealer teaching the ECU? Specifically, my manual says "After you install a new battery, it must be initialized in the control unit. Please contact your authorized Porsche dealer". The guy with the BMW made a case for this when changing the battery size, which I intend to do. Does anyone have any further info on this, or is it possible for an owner to initialize the new battery in the control unit??
Stick with the same "type" of AGM battery that was OEM and there should be no need reprogram.
He also mentioned that some times the start/stop feature needs to be reprogrammed on some cars.
02-22-2018, 12:43 PM
#32
Racer
Thread Starter
- I asked my dealer about reprogramming the car to a new battery and he gave me a quizzical look. So I'm not worried about it... I've had mine for a long time now without reprogramming, no issues...
- The 991 is a battery hog - in fairness all modern cars are. I've installed pigtails for CTEK that stick out of the hood (under the wipers) and I now connect the car in 5 seconds each time I know I won't use it for a few days... I can also get a voltage reading at the pigtail w/o awakening the car, which is more accurate (and still on the low side of things but hey..)
- 11.6V is *very* low... On an old style battery it would be "terminal" (electrical joke!) - that would not start my 1972 911. Surprisingly on the 991 it'll probably start, but it'll make your alternator work super hard and output 14.5V for the entire trip (?). Considering the price and labor of an alternator vs a battery, I know which I'd replace.
I'd disconnect the battery and measure it outside the car, bet it's more like 12.2+ without constant draw... Probably worth a replacement, but since I jumped the gun on mine and yours is a 2015 car, give it a good day long charge on the Ctek anyway and measure again the next day, the next week... 11.6 no bueno, IMO...
- The 991 is a battery hog - in fairness all modern cars are. I've installed pigtails for CTEK that stick out of the hood (under the wipers) and I now connect the car in 5 seconds each time I know I won't use it for a few days... I can also get a voltage reading at the pigtail w/o awakening the car, which is more accurate (and still on the low side of things but hey..)
- 11.6V is *very* low... On an old style battery it would be "terminal" (electrical joke!) - that would not start my 1972 911. Surprisingly on the 991 it'll probably start, but it'll make your alternator work super hard and output 14.5V for the entire trip (?). Considering the price and labor of an alternator vs a battery, I know which I'd replace.
I'd disconnect the battery and measure it outside the car, bet it's more like 12.2+ without constant draw... Probably worth a replacement, but since I jumped the gun on mine and yours is a 2015 car, give it a good day long charge on the Ctek anyway and measure again the next day, the next week... 11.6 no bueno, IMO...
03-06-2018, 10:35 PM
#34
Instructor
same here for my 991.2. During cold weather I tend to see 14.8V-15.1V. During warmer months I see 13.8V-14.3V while running. Car is 10 months old and kept plugged in with a Porsche charger (CTEK), driven a few times during winter when above 40F
03-07-2018, 11:25 AM
#35
Burning Brakes
- I asked my dealer about reprogramming the car to a new battery and he gave me a quizzical look. So I'm not worried about it... I've had mine for a long time now without reprogramming, no issues...
- The 991 is a battery hog - in fairness all modern cars are. I've installed pigtails for CTEK that stick out of the hood (under the wipers) and I now connect the car in 5 seconds each time I know I won't use it for a few days... I can also get a voltage reading at the pigtail w/o awakening the car, which is more accurate (and still on the low side of things but hey..)
- 11.6V is *very* low... On an old style battery it would be "terminal" (electrical joke!) - that would not start my 1972 911. Surprisingly on the 991 it'll probably start, but it'll make your alternator work super hard and output 14.5V for the entire trip (?). Considering the price and labor of an alternator vs a battery, I know which I'd replace.
I'd disconnect the battery and measure it outside the car, bet it's more like 12.2+ without constant draw... Probably worth a replacement, but since I jumped the gun on mine and yours is a 2015 car, give it a good day long charge on the Ctek anyway and measure again the next day, the next week... 11.6 no bueno, IMO...
- The 991 is a battery hog - in fairness all modern cars are. I've installed pigtails for CTEK that stick out of the hood (under the wipers) and I now connect the car in 5 seconds each time I know I won't use it for a few days... I can also get a voltage reading at the pigtail w/o awakening the car, which is more accurate (and still on the low side of things but hey..)
- 11.6V is *very* low... On an old style battery it would be "terminal" (electrical joke!) - that would not start my 1972 911. Surprisingly on the 991 it'll probably start, but it'll make your alternator work super hard and output 14.5V for the entire trip (?). Considering the price and labor of an alternator vs a battery, I know which I'd replace.
I'd disconnect the battery and measure it outside the car, bet it's more like 12.2+ without constant draw... Probably worth a replacement, but since I jumped the gun on mine and yours is a 2015 car, give it a good day long charge on the Ctek anyway and measure again the next day, the next week... 11.6 no bueno, IMO...
03-07-2018, 10:09 PM
#36
03-14-2018, 05:39 PM
#38
Rennlist Member
04-02-2019, 10:47 PM
#40
If you want to stop the guessing game get a battery analyzer for start/stop AGM batteries.
