Returned home after being away for 2 weeks and discovered that the cayenne's battery was completely discharged. No problelm just put the battery charger on and situation should be remedied. Not so... when I hooked up my charger (on the 11 amp setting) all the electronic systems in the car go wonky. The headlights randomly go on and off, sometime blinking from side to side, the nav screen attempts to come on in a distorted staticy way, and warning lights blink on and off. I disconnected the charger after a few minutes as things were not stabilizing. Anyone have any idea what would cause this or potential solutions?

 

11 amps is a lot to throw at a battery with the rest of the car's system connected. My guess is that it took some pretty high voltage to push 11 amps through; and you may have fried something in the process.

I'll never go above 13.6 volts and 3-4 amps with my battery connected to the car. If I want to push it higher or faster, I'll disconnect the battery from the system

 

i'd never recharge a battery, replacing is the best way to go, especially in your case, 2 weeks is NOTHING for a battery. I leave my cayenne for 4 months without touching and nothing happens to battery.

 

There should be no problem with charging your battery after it being discharged for only 2 weeks. That is not enough time to cause any real amage to the plates inside the battery. The unfortunate part is that while the battery was discharged many/all you conrtol units in your car (just around 47 in total) may have lost much of there programming. What you will have to do at this point is bring the vehicle to a Porsche Dealer or Certified Shop with Porsche Vehicle Testers to preform a "Vehicle Handover" and recode/wake up the units. There really is no way around this unfortunately.

 

Problem seems to have been resolved. In order to get the seat back to disconnect the battery cables, I needed to supply power using jumper cables. Although the car would not start when I connected the cables, all the blinking and stuttering electrics did settle down. I left the cables on for about 10 minutes and when, as an experiment, I re-tried the starter it worked. took her out for a half -hour drive and when I turned her off she was still able to re-start on her own. I'm thinking my battery charger may have been at least part of the problem but it had always worked before??/
If I have any problems with other systems as you suggest will happen, i'll look into the recoding/"Vehicle handover". I was having some trouble with the itronic bluetooth on the drive but that may be unrelated.

Thanks again for you help folks