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The high voltage readings

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With the CURVEN8R coming up on 6 years old, I'll probably have to replace the battery before to long.

The manual for the 981 states that after a new battery is installed, it must be to be initialized in the control unit. Do you need a PIWIS for this?
Wish I could help--but our 981's original battery is still charging (knock on wood)
Paging Laz...
More knocking
Laz - 2 weeks ago
My 13 is still good, some of which I attribute to keeping it on a maintainer if the car’s not driven for more than a couple days.
The battery in my Honda is about 10, and gets the same treatment.
Last week, right after mentioning to a friend that I rarely experience flats, one of the Boxster’s winter Michelins picked up a large screw. I now expect both batteries will die in the next couple days!
Thanks Mike and Laz,

Snow and salt are almost gone here. They're calling for rain tomorrow, that should wash the salt off the roads, and a Spring heat wave, around 60 F, coming Saturday and Sunday. So I expect to get the Boxster out then. I didn't have any problems starting the car before I put it away and I've always put a battery maintainer on it if it was going to sit more than 4 or 5 days. The only thing that made me wonder was the high voltage readings (14.4 - 15.0 V I was starting to get while driving the last month or so before I stored the car. So I thought I'd start doing some research before I might have to buy a replacement, in case those readings indicate a possible battery problem.
I think there was a discussion here a couple years ago about this. My car has displayed into the 14s, too, and my dealer said this was ok, and nothing to worry about. If I correctly recall, the first instances of high readings occurred while coming down a multi-mile downhill part of an interstate. Something to do with "electrical system recuperation" and/or the "generator" (Porsche's terms) helping with engine braking.
Although the image below mentions the PDK coasting function, it's still relevant to stick shifts:

Thanks, Laz. My readings were usually in the 13.5 - 14.2 V range. When driving in Sport mode, the Voltage would rise by about 0.5 V. Then, starting mid October, I'd watch the voltage creep up as I was driving, even just steady state highway driving. often sitting at a steady 15.0 V.

I'll keep an eye on it. I should be able to take the car out this weekend.

I know I don't like replacing things like batteries unless it's necessary, not only for my wallet, but the environment as well. I had a Jetta, where the battery lasted 10 years.
14.X voltage....
Petee_C - 2 weeks ago
my radar detector displays 14.x volts when driving at highway speeds on all my vehicles....

I think that's normal.
My 981 Boxster is a late 2012 build and has 57,000km. The car is showing symptoms similar to Guenter in that it occasionly shows voltages of 14.8 to 15v, and then drops back after some time to 13+/- while cruising. It started doing this last fall. I don't normally use auto stop, and store it for the winter on a maintainer.

My gut instinct is to keep driving and just keep an eye on it. Auto stop still works if I let it.

[batteryuniversity.com]



Edited 1 time(s). Last edit at 04/08/2019 12:42PM by Tweety. (view changes)

13 Boxster, Racing Yellow, PDK, SC in yellow, 20" Carrera platinum wheels, sport steering wheel, yellow seat belts, yellow roll bars, 14 way power seats, PDL, sports tailpipe
The long downhill high readings occurred years and many miles ago. I don’t think it’s a sign of a failing battery.
There’ve been other occurrences, too, although I haven’t taken notice lately.

Minus 40 degrees... Is that Fahrenheit or Celsius?
Quote
Tweety
My 981 Boxster is a late 2012 build and has 57,000km. The car is showing symptoms similar to Guenter in that it occasionly shows voltages of 14.8 to 15v, and then drops back after some time to 13+/- while cruising. It started doing this last fall. I don't normally use auto stop, and store it for the winter on a maintainer.

My gut instinct is to keep driving and just keep an eye on it. Auto stop still works if I let it.

[batteryuniversity.com]

Interesting. Mine was a June 2013 build. Mine has just over 81,000 km. Sounds like your symptoms are similar to mine. Yesterday I had just removed the maintainer. On start up ( fired right up as if I had just parked it the day before.) it started at 14.2V. Then steadily climbed to and stayed between 14.9 and 15.0V for the rest of the 100km drive. It didn't matter if I was accelerating, cruising, coasting down or at idle. I haven't tried auto stop.

Like you, I don't normally use auto start/stop and store it on a maintainer for the winter or if it's going to be sitting for more than a week.

I'll just keep an eye on it.
If you install the same type of battery with very close to the same specs you can just swap them.
Keep in mind that your battery is a GMA type battery. Look at the CCAs and get a match.
If you decide to go with a traditional (cheaper) lead-acid then you'll need the PIWIS to reprogram the alternator's charging characteristics and the DME's voltage controls.
Happy Boxstering,
Pedro

Pedro Bonilla 1998 Boxster 986 - 287,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

Racecar spelled backwards is Racecar
"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"
"If you wait, all that happens is that you get older"... Mario Andretti
"Being second is to be the first of the ones who lose" ... Ayrton Senna
Quote
Pedro (Weston, FL)
If you install the same type of battery with very close to the same specs you can just swap them.
Keep in mind that your battery is a GMA type battery. Look at the CCAs and get a match.
If you decide to go with a traditional (cheaper) lead-acid then you'll need the PIWIS to reprogram the alternator's charging characteristics and the DME's voltage controls.
Happy Boxstering,
Pedro

Tough choice for a renowned penny pincher winking smiley

"A mile of highway will take you one mile. A mile of runway will take you anywhere."
Thanks Pedro. That makes sense - requiring the same specs. I just wasn't sure if the PIWIS reprograming had anything to do with letting the system know that the replacement is a new battery, requiring some type of charging compensation compared to an old battery.

I know with my old 987, it was a pretty simple swap and didn't seem to need any window resets as the manual had suggested. Only the DME took a few miles to "learn" my driving style again.


Pedro Bonilla 1998 Boxster 986 - 287,000+ miles: http://www.PedrosGarage.com
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

Racecar spelled backwards is Racecar
"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"
"If you wait, all that happens is that you get older"... Mario Andretti
"Being second is to be the first of the ones who lose" ... Ayrton Senna
Very interesting subject. I asked this specific question of the shop foreman at our local dealership. This was his response:

"I just noticed that we didn't cover your question, but to answer it, I do not know of an aftermarket scan tool that will register a new battery to the vehicle. I'm sure by now there is someone out there and it's definitely important. If the charging output of the alternator is not reset the battery may never receive a full charge which will act like a bad battery. If someone replaced a battery themselves and needed it reset here, we'd charge 1/2 hour for labor as long as the battery can be registered."

I see what Pedro is saying above. I think what can be confusing is that some folks call this feature "battery aging compensation" or something similar. From what I hear Pedro saying it is "battery matching". Makes sense to me. Thanks Pedro.

Now if we could find a workaround for putting the electricity parking brake in the service position when replacing the rear rotors.
maybe do a load test on it 1st...

if the battery location is anything like the 986 series, then it would be away from any battery killing heat.....

I would say keep it until you start seeing problems.... maybe have a battery booster pack in case...

I hate spending money on stuff that doesn't *need* to be replaced....

some data, though not totally related....
my wife had a 11 q7 that we returned last year due to the dieselgate scandal... still original battery with 220K km on the clock.... We had to charge it once due to some weird drain that never came back... it was under the driver seat, and would have needed to be registered if we had changed it out....
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