deilenberger

Since this didn't seem to get any traction adding it to an existing thread, perhaps it will do better if I start a new thread.

I made the mistake of displaying the system voltage on the multi-instrument-display.. and noticed on startup that the voltage appears to be around 12V. Once started it comes right up to 13.6-14.8V - so I'm guessing the display is fairly accurate (and I compared it to my DVM - and they read the same.)

Car starts and runs fine - but going on a road trip in a few weeks, so a preventive battery replacement appears to be in order soon.

Question - to those who have replaced their batteries on the 958 series: Is there a vent tube? I've looked at a lot of AGM batteries (it appears there are two manufacturers pasting different brand labels on two basic AGM size 49 batteries) - and on some of them there is a "Vent Tube Required" notice. I know various flooded-cell batteries always had a vent tube - did the OE AGM battery use one?

Also - what did the dealer charge to reset the "registration" of the battery? It's probably not critical as long as you stay with the same type (AGM vs flooded - AGM uses a higher charge voltage) - but probably still worth having done.

TIA!

deilenberger

I can answer the vent tube question - yes there is a vent tube. Happily the standard for the Type 49 design seems to be tight enough that the existing vent tube fit just fine. As did the plug for the vent in the other end of the battery.

Still no answer on "registration"..

The DIY https://rennlist.com/forums/cayenne-...nt-access.html was quite helpful, although doing it is much like on a 955.

Zingari

I'm not sure why you would be worried about the battery with those readings. They look normal to me and mine regularly goes up to +14v? I doubt there will be a 958 owner who has yet to change a defective/sluggish battery.

Does the stop/start still operate? One of the pre-conditions (amongst several others) is that there is enough charge in the battery to maintain equipment when the engine switches off.

If it cranks without feeling sluggish then I'd surmise your battery is OK. I dont know how long Porsche batteries last but my diesei Audi is still on its original battery at 13yrs old. My wife's Audi battery was changed last year because of the very short journey's she does so and not driven long enough to give it a decent charge - this car is 12yrs old!

If you have Porsche extended warranty it will need to be a Porsche supplied battery which will cost at least 3 x amount of a similar sized battery bought elsewhere as non genuine batteries in the UK invalidate the warranty

deilenberger

Hi Zingari,

I've already changed the battery - to a new AGM, which is vented, but since it was physically identical to the old one - the vent hose moved right over, as did the plug for the other vent hole in the battery.

I've spotted something else "interesting" - and it's designed in by Porsche. You can try it on your 958..

Put the voltmeter up in the multi-instrument display. Whilst driving down the road, observe what the charge voltage is. Then press your "Sport" button and observe it. See anything odd? I can tell you it's not due to different load draw, it's not due to the change in engine RPM - it's programmed to do what you see.

Once you see it - let me know and I'll explain the "why" of it.. (what I figured out to be the only logical explanation..) assuming things are the same on your side of the pond.

125shifter

Don, what battery did you replace it with? Did you have to have Porsche 'register' the battery after replacement? I checked the Durametric website and didn't see anything listed for battery replacement function.

My battery is original from 2010 so I'm thinking of replacing for peace of mind. I got a price from the dealer for the Porsche battery of $540 or installed for $900.

gnat

Haven't done that, but are you talking about the volts dropping considerably below the standard 14.4v and almost to 12v?

If so, you don't need to be in Sport Mode for that to happen. First time I saw it was in the middle of a 1k mile leg home. Scared the crap out of me as I thought we were going to be broken down on the side of the road with 3 dogs and an infant

Apparently it can under certain circumstances disengage the alternator so that it is not a drain on the engine. The two general circumstances are for increased MPG while cruising and during periods of power demand. At least that's how the dealer explained it to me at the time.

Given the problems I had with alternators (self inflicted) in the Escape that the P!g replace, I'm constantly watching the voltmeter and I still twitch when I catch it doing that

gnat

Are you sure this is needed? I've heard that at least the 958.1 doesn't have that silly requirement (we have a BMW that does and it pisses me off that something as simple as changing the battery is a giant PITA).

In the US this is not true. We have a law in place (Magnuson-Moss Warranty Act) that says we can use any 3rd party parts so long as they meet the MFG standards without impacting the warranty. It also allows us to take the vehicle to any shop (or DIY) without voiding the warranty as long as MFG procedures are followed.

deilenberger

Gnat..

Somewhere I 'splained what If found out from several Porsche service centers.

There is what appears to be battery "registration" in the Cayenne - but it's bogus. And it can't be changed, even with a PIWIS.

The PIWIS, the iCarScan, the SnapOn scanner - all have a function to write new battery information to the gateway. Thing is - the gateway doesn't accept it and change anything. There are values in several fields, the manufacturer's name of the battery, the type, the CCA - but they can't be changed.

The reason it can't be changed is - the software ignores those values, and uses parameters designed for maximum fuel economy.

When I first installed the new AGM battery in my '11 CTT, I made note of a 1V difference in charge voltage, depending if the car was in normal mode or sport mode. In normal mode - it was consistently 1V lower then in sport mode.

That was with a new battery that apparently hadn't been fully charged.

Once the battery was fully charged - the voltage in both modes often sits right around what battery voltage would normally be (12.6V) and switching from normal to sport doesn't change anything.

What Porsche did - was restricted the alternator output (and reduced the load on the engine) in normal mode, which is where fuel economy and emissions tests would be run. They let it charge unfettered in sport mode.

So - "registering" the battery really made no difference. It isn't used to control the charging rate/voltage.

I called 3 dealer service departments and asked the service managers (not the service-sales-advisers) if they did registration on Porsche batteries. To a one - I got a "huh? Oh, no... we just put it in.." I tried 3 different tools to change the values - none of them "took".

So I've forgottenaboutit.. and that was about 25,000 miles ago, and all is working just fine.

gnat

Damn it! Bitten by a necro thread!

stronbl

Interesting ... I just replaced my OEM battery after 5 yrs. My dealer said they had to register it with the car. They charged me $25.

deilenberger

It is interesting.. 3 dealers (actually the service managers, not the service "advisers") - said "Huh?" when I called them.

I'd love to hookup the iCarScan to your vehicle, IIRC - the "registration" has multiple slots - so you could look back and see if the battery was changed and when. Problem was - couldn't write to those slots. If they did on yours, that should show up.

Kirill

Curious if now you can read these values with a scanner, or if it was some kind of witchcraft.

deilenberger

I think that's what I said right above ^^^ but longer..

Kirill

I think I am going to try to pull values from my GTS, factory battery should be registered too.
So far I am going with a theory that honest dealers say there is no need to register battery, others charge 25$ for it and may be submit battery change record to Carfax

projekt-h

Interesting info. From what I'd read previously they "learn" the charge parameters to the battery's specific capacities and reset it to account for degradation over time. guess that was a buncha malarky. Didn't really seem to make sense, considering it's probably just semi-advanced voltage monitoring. Good to know for future use. I think the one in my car has already been changed, can't tell what's in there now but it doesn't look like a Porsche battery, and the cover seems askew.