ByronD

Hey guys,

I have a 2014 991S... I usually drive this car at least once a week on the minimum, and I have owned this car 3 years now... and as of a few months ago I notice the battery charging reading on my dash to be on the higher end of the range. Does this mean my battery is dying and I should replace it?

The car does at times struggle just a bit to start the first time after a few days... but once I drive it there is no issues.




Should I just keep going with my life the way it is? Or this higher reading is trying to tell me to change my battery bc it might die soon lol

Also what number should the charge read on a normal basis?

Thanks!

MingusDew

New battery is $250’ish and takes 10 min to swap. It’s the first thing I do with any new car I purchase. Cheap and easy insurance against problems, and I know with a new battery approximately how long to expect until needing a new one. If you’ve had the car 3 years and never replaced the battery just go ahead and do it, why waste time thinking about something cheap and easy.

asellus

7-10 years is a reasonable lifespan for that battery. Consider replacement if you're in that range.

Otherwise, the charging voltages will be higher in colder temperatures. Just the nature of the battery.

IXLR8

So with it only being 3 years only, it has been replaced at least once. FYI, your 991 is one year older than my 991 which is still on the original battery.

Your voltage is not high for an ambient temperature of 69F. In fact 14.6V is spot on.

ByronD

Awesome guys thank you guys.. just wanted to make sure that the reading was in range to were it should be....

JimEb

Were you in Sport Plus mode?

Been many discussions on the phenomenon but never heard a good explanation why the charging voltage goes up in Sport Plus. I’ve seen it first hand in my ‘14 C2.

ByronD

That reading is like that from the moment I turn on the car no matter what mode Im on.... and if Im driving or sitting still

asellus

In drive mode, the alternator is opportunistically engaged to charge the battery, since having it engaged full time will lower economy. This means it'll engage during downhill coasting, braking, likely during WOT, when there are increased electrical demands (turn on your seat heaters and rear defrost, for example), or when the battery is below whatever target state of charge the engineers at Porsche have decided is "too low"

There's a lot of rhetoric about how the car "needs maximum power for maximum performance" but there has yet to be any actual evidence or documentation from Porsche proving this, just some random internet people regurgitating the same crap.

Antigravity

Well you sort of answered the question yourself. There are more loads in Sport Mode, just as there are more load when the A/C goes on so voltage goes up to compensate. You can verify this simply by seeing the voltage go up when in Sports Mode as oppossed to regular mode.

IXLR8

^ In any case, whatever mode it is in you cannot exceed the charge voltage which is based on battery temperature, in this case ambient temperature since the battery is not in an engine compartment being heated.