sdiamond

Hello everyone, 2012 CTT sat for a week and battery or something has left the building… no dash lights and on opening door, nothing. Put on trickle charger 24-36 hours still nothing. Connected jumpers and key fob locks and unlocks, headlight gets go on when turning the dummy key but still nothing on the dash. Is it something like an immobilized system? Looks to be a pita to replace battery under seat so looking for help before going that route. HELP please

CAVU

The majority of battery chargers being sold will not start a charge cycle until it "tests" the battery and it is above that charger's threshold to start charging, greater than 8-11 volts (decent reference https://www.chargingchargers.com/tut...cognition.html). Most chargers will let you know with its status lights what it is and is not doing.

Should you have a battery that has discharged below your chargers threshold, simply perform a "Force Charge" with a healthy 12v batteryusing jumper cables. Using the charge/jumper posts under the hood, connect the cables to the posts positive to positive, negative to negative for about 30-60 minutes. Remove the jumper cables, attach the charger and let it finish topping off the battery. If you have one, test the battery after the charging is complete.

Yes to all of the following, and I am sure there are more:
- letting your battery get that low on charge is not good for the battery. Who knows how much longer it will last
- if there is an internal failure in the battery, this will not work.
- DO NOT TRY THIS THROUGH THE cockpit 12v lighter
- If you are not near a shop or at home and the battery has drained by something left on, this can work if some kind soul is willing to hook up jumper cables, force charge, get you started and let the alternator take over, BUT put the battery on a charger when you get to the shop or to home.

sdiamond

That makes sense about a charger needing a certain base voltage but how come a jump with cables didn’t give anything to light up the dash or fire the starter?

Norge911

Battery under seat is not too bad. Probably need to connect a healthy battery to the jumping stubs to get this done.

connect healthy battery to jumping stubs under hood.
Slide seat forward and unscrew the two rear bolts. I think this is E torx socket.

slide seat all the way back and tilt seatback all the way forward
undo two forward bolts. Then tilt entire seat back and lean against back seat.
disconnect the heathy battery before proceeding to remove battery under seat.

Good luck

Norge911

May need to charge dead battery for some time in order to be able to get starter to turn or
if battery is damaged from going completely dead, may not transmit enough energy through battery in order to be able to crank even with another battery connected.

CAVU

One good battery jumpered to a dead, very low voltage battery, will not yield enough amps and volts.

sdiamond

okay, assuming that the current battery is shot, I'm okay with replacing, what are the recommended (by everyone) replacement? Interstate, Optima, ?? and how do I know before pulling out old one if it is an H7 H8 or H9?

Franko T

https://rennlist.com/forums/cayenne-...m-battery.html

CAVU

Compartment can handle up to H9.

Go to walmart and buy their H8 AGM and you will be good to go.

987fav

I had a similar issue with my boxster. When the battery is completely dead like this you have to swap it for a new one. I tried everything to get the battery to charge again and it didn't work.

One thing that might make this easy (its what I did). I just called my insurance company. Depending on what you have they have services to get you on the road again and if you need a new battery they just swap it out right on the spot (barring the battery cost), but they'll get to your battery (in my case the electronic frunk wouldn't open due to the dead battery and they got it back open for me via the emergency terminals). It was super easy. Hope this helps you!

sdiamond

Here's another issue, connected my wife's car battery to the Cayenne and still nothin more than headlights come on.
still no dash lights
can't move the electric seat to get to or remove battery.....
front bolts exposed but not the rear
why with a good battery with 13.9 volts coming over will it not light the dash or seats none the less start the car

sdiamond

If i put a battery charger on the under the hood connections will that power the seats?
is there any emergency release for moving the front seat?
any recommendations for a charger specifications for what is a flat line battery 10A 20A ???

CAVU

OP,

- The 13.9 volts does not make since to me, unless you were jumping from her car to yours and her engine was running. Was that the case? If you battery is DEAD, then even good battery will not likely get the job done since it is connected to a battery that will quickly drain the life out of the good battery and store nothing.
- I would recommend not using a battery charger as a power source. battery charger voltage and amp supply are not stable unless you have a purpose built large amp dual charger/power-supply.
- With no external power/charging sources connected, what voltage are you seeing at the under hood jump points?
- Any recent servicing or new gadgets added? anything connected to the 12v outlets in the cockpit?
- If you have access to a 12v auto battery tester (amazon has them for $25-$35), connect it to the under hood jump points and get/share the readings.
- Did anyone disconnect the negative chassis lug in the drivers floor? Is it loose? It is under a precut area of the carpet near the seat.
- Any chance the key fob is bricked or the wrong fob?
- Have you checked the related fuses in the left and right side of the dashboard and in the engine compartment
- If you have a AAA membership or equivalent, they show up with a battery tester and a battery.
- Double check that the car is in Park.
- Do you have an antitheft device installed? Did a previous owner install one and you are not aware of it? I found the previous owners device by tracing the OBDII cable wiring to find a splice which led me to the black box and the rest of the wiring.

sdiamond

Okay if I can start over..
if the key fob opens and locks the doors and the head lights go on but the dash is black, interior lights nothing,
I connected jumpers from the Rover which shows 12.5V with car off and 13.7 when other car running. Neither way gives power to the Porsche. Obviously can’t move seat to access the battery. Could it be a fuse somewhere? Why would a connected jumper not even light the dash? Evidently you can (maybe) access the forward rearward motor and power it directly. That is if I can even reach or find it.
totally confused and frustrated so any help is greatly appreciated

CAVU

hang in there. I left you with a laundry list of questions. Grab answers for the easy ones. It may not be the battery, but need to eliminate it as a candidate.

Really need to get a digital battery tester on the battery jumper terminal and take some readings, AND check a few fuses (page 288ish in the owners manual).