New to Bimmerforum

[M73 V12]

Great site with lots of good info. Just wanted to take time out to introduce the car. 01 750IL. 68K miles. Working on replacing various deteriorated trim pieces around windshield, gutter and a broken rear passenger quarter sun shade. Also currently working on an intermittent no start but based on what I've read and symptoms and testing I learned from here I think I'm dealing with a dead battery or a faulty battery switch. Hence the dead battery.

[CPHES]

Make sure your terminal connections are clean and tight. You need to measure the current draw after the car goes to sleep.

[acspecialists]

Ditch the second battery and the switch. I ditched mine and have had no ill effects.

[M73 V12]

As in...go to a one battery setup? you have my attention.

All connections are clean and secure. No water ingress in either of the locations for possible fuse issues. I'm just in the research phase of this as it has now left me needing a jump (at random times) 3X now. All jumping from engine bay terminals which I believe go straight to the starter. 3d no start the interior electronics actually went dead in the process. Both batteries were replaced almost 4 years ago. But car is barely driven so compromised batteries a very good possibility. I drive it about once a week but hope to drive it a lot more.

[chrisn7]

Batteries require looking after in these cars, and yours were presumably flat since you tried jump starting. Replace both so you know you are starting from a known good position, and then keep them in condition with a smart charger.

Battery switches are pretty reliable, and I wouldn't recommend ditching it yet until you can prove its faulty, as they are no longer available from BMW. You can read all you ever wanted to know about the function of the switch in the newtis site.

Quarter blind failure is common as there is insufficient plastic to stop the spindle turning under load, but its an easy fix using a filler of your choice. When the vertical cover is removed (newtis again), for future reference note the hidden screw at the bottom that retains (or should retain) the door card

[acspecialists]

The battery switch is a consumer so yes if you put a charger on it you should be fine.

When I got my car it would do nothing until I put the key in and then the car would come to life and start fine. The top battery was so dead it would not even charge. Before dumping $150 on a high quality AGM I thought maybe I would try ditching the battery. It has been several weeks with periodic starts and I have had no problems. I removed the switch and installed a jumper cable from the positive posts. After a few months I may install a more permanent set up.