visitador

Just trying to figure out what should be the normal voltage before I start the CD's engine. Trying to figure out if a battery replacement is due soon or not. Thanks

ScootCherHienie

You can't really go by battery voltage. The battery needs a load test but it has to be done at the battery terminals, not using the under-hood jump start/charging terminals. With the battery being under the driver's seat, that's not all that convenient. A lot of trim and a cover over the battery have to be removed to get access to the battery... and 2 bolts holding the back of the seat legs have to be removed so the seat can be tilted forward to get at the battery. A lot of car parts stores will do free load testing on a battery hoping you will purchase a battery from them if you need one. Advance Auto Parts has a really good AGM battery for 1/3 the price of a Porsche batter (more than likely made by Bosch). The mild climate in the Bay Area should allow your battery to last for 8 years or so since the battery is inside the car rather than under the hood. If you don't know how old your battery is, they have a manufacture date sticker somewhere on the outside of the battery that should reveal how old the battery is.

visitador

Thanks for the reply. I was just trying to do a ballpark comparison. My 991 shows 12.+ while the CD shows 11.+ before starting engine. I know from the 991 forum that is normal. Just trying to figure out whether the slightly lower value I see in the CD is ok or not

Btw, I do use a CTEK battery charger on both of them

ScootCherHienie

All batte4ries (conventional batteries) put out around 12.5 volts. But voltage is no indicator of battery condition unless the voltage is low and stays low all the time. You can have a battery that measures 12.5 to 12.8 volts and it can be in really bad condition. That's why you need a load test to tell if the battery is good or not. Good voltage doesn't mean a good battery. Bad voltage MAY mean the battery is bad. Measuring voltage at the posts under the hood may or may not tell you the real battery voltage... the underhood posts definitely should NOT be used for the load test, you have to connect directly to the battery terminals under the driver's seat. If you have REAL low battery voltage on a Cayenne (my experience is with a 957 series) you get lots of errors about various lights not working and the motorized tail gate may fail to operate (in the 957, the motorized tail gate is the first thing you have trouble with when a battery is not charging fully, this is in the owner's manual). If you have a 957 (don't know if other series are the same or not) and you aren't having trouble with warnings about brake lights, front side lights, or other lights and/or problems opening the tail gate, chances are the battery is OK. But voltage, especially at the terminals under the hood is not a good indicator of battery condition.

Chensley

I’ve got a 957 that has had intermittent side marker light and very rare rear brake light errors only to see them disappear. Now just today had a couple instances where it cranked over then The starter stopped before starting. Took several tries before it finally did start. I had just replaced the starter three weeks ago so I was first dreading that it could be the cause but now after doing some research and reading your post, I think I’m leaning towards a battery issue now. Like you mentioned volts are strong when checking them at the jump terminals. I need to get into the actual battery now to load test it.

JamesN

I have a 2016 CD with original battery and 42000 miles. Voltage on the dash shows 14.8v. it may occasionally drop to 14.5, but will go back up. Never higher than 14.8. It starts just fine and all lights/tailgate work fine. Should I be concerned with winter approaching?

thanks
jim

ScootCherHienie

Having the battery protected inside the car makes them last a fairly long time compared to batteries that are under the hood with the engine. Figure closer to 8 years in average climate, not too cold, not too hot. Knock a year or 2 off of that if you live somewhere very hot or very cold. Most car parts stores can perform a battery load test to determine how robust the battery still is, but doing that PROPERLY requires accessing the battery that is under the left hand seat in the 957 series, not sure where it is in the 958, but presume under a seat or in the cargo area. If the shop doing the test for you uses the jumper posts under the hood, they can get false test results.

BTW... Porsche dealers want around $600 for a replacement battery... but you can find the same Bosch battery for less than $250 and the Duralast brand sold by Advanced Auto and Carquest can be as low as $180 when on sale. You want an AGM battery or an Odyssey or Optima spiral cell battery... do not get a battery with liquid acid... you don't want that leaking gasses into your interior. No need to accept the ripoff price from the dealer--the "Porsche" battery is just a Bosch battery with equivalent replacements being just as good. On 957s, battery cross reference charts say the H8 size is correct, but they are ALL WRONG... the original battery in 957s was an H9, same battery, but 2 inches longer. Before replacing your battery, look for model number designation to insure you get the same size replacement.

Gary958.2 S

I just got my 2016 Cayenne, but an S rather than diesel quoted by Jim above. I presume Jim that you are talking about the voltage displayed (in the Multifunction gauge) while the car is running. That would be an appropriate voltage for any car that the battery (even a bad one) reaches after a few minutes of the alternator pushing out 14.6 to 14.8. But what does the voltage do when you turn the motor off, but leave the ignition turned on to see the gauge? I'm seeing my "S"go down very quickly, particularly if I use Start/Stop, but even if not. It goes down to low 12V region VERY quickly (a minute or two). In normal battery discussions, anything below 12V is a dead/dying battery. When I restart the motor, it takes a minute or two to climb back over 13V, and quite a bit longer, 3-4 mins, to get back up to over 14V. I am thinking I'll need a new battery, but plan to watch it for a bit, and do a few more tests/diagnostic readings/load test.

Do others experience this fast a drawdown? I know the Cayenne has a lot of things drawing voltage, but this seems way too fast to me.

Gary

rennsport44

I also have a 2016 Cayenne S and also would like some reassurance everything is doing what its supposed to do. I just replaced the car's original battery 4 days ago with an Interstate MTX-95R H9 AGM battery (950cca 100Ah). $239 from Interstate. I decided to replace it after the dealer told me my battery was at around 50%. They wanted $800 to do the job.

After I replaced it in my driveway (have not "registered" the battery), when I switch on ignition (not start) in the morning, it reads 12.6 and within 2min it creeps down to 12.4-12.2. When I start engine, it climbs up to 14v or so and will settle down in the mid-high 13v range after 30 secs of engine idling.

For the first 2 days after I replaced it, the volts read 13v while driving and pretty much stayed there. For the last two days its been hanging in the high 13v low 14v range while driving, which is about where the old battery would read while driving as well

Im curious to hear what others think of these numbers. I want to be sure everything is operating as it should.

Tim Matar

Rennsport, watch battery voltage on dash display, switch to sport mode and watch the alternator charge rate go up above 14v. I read this in another post by deilenberger last night and confirmed same on my car. Behaviour is same on mine as yours but the battery may need a good run to fully charge. In normal mode it is trying to conserve fuel by reducing alternator load on engine.