^^The battery in my ML320 Diesel SUV is under the front passengers seat. So unless you have a midget wife (Sorry small person wife) there is no way to get the seat far enough forward and high enough to access the battery compartment.
There is a positive terminal in engine compartment BUT will not charge the battery or jump the car/battery.
I squeezed my hands under front seat and was able to get the cover plate off battery and barely get charger clamps on terminals. That gave it enough juice to move seat.

 

Thanks, it seemed odd to me to see mention of coding or modifications (not needed in case of Interstate) on Rennlist (https://rennlist.com/how-tos/a/porsc...-to-use-376529) since the connection is purely electric but I wanted to make sure before I run over to Sam's Club.

 

Based on the info posted in this thread, it would seem like a standing draw of 40mA is an accepted norm. Just wondering if anyone has taken the time to methodically pull each fuse while using a multi-meter to identify which circuit (s) / component (s) are responsible for this draw? I'm afraid I do not have a workshop manual.

 

Not to go OT but recently my wifes Mercedes E320 Diesel experienced battery drain overnight and voltage was 8 volts in the morning no start. It's a ew battery 3 months old and nothing out of ordinary was turned on or left on. Draw was about 3 amps with engine and accessories off.
Battery took full charge so not a bad battery.
*So did some digging on Youtube and come to find out 2003-2012 Mercedes E320 have issue with parasitic draw from passengers seat module not turning off. I pulled the fuse, waited 30 minutes and the battery draw went down to .30
I wouldn''t hesitate and great idea to pull fuses on my 997 to determine excessive draw. Easy to do but time consuming because you need to let car sit for 30 minutes after pulling EACH fuse to allow the car's computer to settle.

 

If the car is not a DD, then just try one fuse per day and eventually get through them. please share any findings.

I discovered a very strange issue with my 987.1, with the ECU acting squirrely. I don't know what else to call it. battery fully charged, insert key, sometimes acts like the battery is dead, but the battery is charged.

The next day, I was kind of fed up with the car and haven't driven it in a while but, the next day I used the key fob to unlock it. and the car is in my garage and I always leave the Windows down and the front trunk popped but I lock it to reduce ambient draw.

well the key fob didn't work, pressed unlock a few times and nothing, had to walk right up close beside the car to get it to work. well, it needed a battery, and that was the whole problem with the ECU acting strange. The key was intermittently losing contact due to a low battery. and there was no alert.

just a suggestion, anyone having bizarre issues with the battery, replace the key fob batteries because that causes bizarre behavior. it's just one more thing you can try if you are frustrated like I was. after that, I left the car for 7 days without the trickle charger and finally the battery dropped to 11.2 V. down from 12.7 or so normally. 1.5V over 7 days. it's not bad. at least it's behaving consistently now.

 

These vehicles will enter a sleep state after a period of a week or more, after which the key fob will no longer operate the locks remotely. You simply lift a door handle and the key sensor will reactivate and the fob operates as normal. That is what could have happened based on your description. If you unlocked the car manually with the key, that will additionally reactivate the key sensor. The key battery replacement most likely did not fix the issue, but it's always good to keep these batteries fresh.

 

Leaving the key in the ignition will cause systems to drain the battery.

 

it wasn't the sleep state. The weak battery in the key fob caused the ECU to malfunction. My guess is it's security related. I thought I was having serious battery problems. but the whole time it was a key fob issue. just saying, before replacing that expensive car battery, check your symptoms. plugging in a trickle charger and having it fail two or three times also does not definitely mean a bad battery. If I let my battery run down completely it takes three or four retries to get the trickle charger to wake it back up.

 

can't imagine why anyone would do that but yeah I'm sure it will worsen the drain.

 

This might help:

 

Having watched the video, it is pretty clear that the methodical fuse pull is the best way to identify the culprit. The culprit could be different for all of us, but given the history of water damage due to blocked drains, I would suggest that those modules that are subject to water damage might be a good starting point. In the video, it was the alarm keeping the module awake. Some things are never really easy.
It would be nice if Porsche could indicate exactly what the sitting draw for the car was when it left the factory. If we had that, we would all know what the baseline actually is.

 

45mA.

 

The first step would be to identify the circuit. This is done by measuring the current draw and comparing it to the factory specs. (Measurements taken at each fuse, or by pulling all fuses except the circuit you're working on.) After the circuit is identified then the tech drills down to the device level. A trained, experienced tech can probably do this in 4-8 hours. Of course, there's always nuance - eg, whether the excessive draw is occurring when the car is locked/sleeping vs. awake.

 

I had similar problems with the battery that came with my 2006 Cayman. constant nuisance. The battery date code was 2021 and started noticing the battery problem shortly after buying the car in middle 2022 so the battery should have only been a year old but, the AGM batteries become ruined if the voltage drops too low and there's no bringing them back to life, they are permanently damaged after that. so that must have been what happened to this battery it was allowed to drain too far down.

I bought a new AGM for it and all of the problems went away instantly. it holds a charge for 3-4 weeks before it drops below 12.0V. I have a CTEK tender that hardly needs to get used on it. recently I've taken the battery out because the car has been sitting for a while and it's more convenient to keep the battery serviced on my workbench with all of the other batteries.