superchet

I have an '07 S65 and the red battery light is coming up. Massage seats don't work and today, I got a message in the command center saying that the command center would shut down in 3 minutes if I didn't start the engine. I was driving at that point and three minutes later, the command center did shut down. Which battery controls these functions? Is this a dealer issue or can I recharge the battery? Thanks in advance!

whoover

If the car is running when COMAND shuts down, it sounds like the alternator or some other problem with the charging system. It's conceivable the systems battery is so failed that it's acting like a short and preventing the consumers from getting voltage from the alternator. It's also possible that any of a number of other components from SAM to battery control module are to blame. You need to have the car scanned for codes. If it is a shorted battery, that could kill the alternator quickly, so sooner rather than later.

UNderdog

2007 has the battery under hood for starting only. Behind back seats in the trunk there is a larger battery which runs the rest of the car. That would be where I'd start troubleshooting. My starter battery up front lasts maybe 3 years. My trunk battery is still original in my 2008 so they do last a while but of course not forever. There's also a small battery somewhere behind the dash on the driver's side behind the fuse panel that I believe is supposed to allow the car to shift into N to move it in case everything's totally dead. If that's original I'd replace it along with the trunk battery.

whoover

There are only two batteries. The aux battery in the trunk was moved to the dash in facelift models. One or the other.

JohnLane

OP... Start with checking voltage as it runs. If command is not working measure voltage across battery in trunk. Should be 14 volts at idle.

alternator is likely dead.

superchet

Major issues on a short drive today. Power steering and ABS off. Engine fluttering and eventually stalling. Going into dealership tomorrow.

Thx for everyone's advice.

Rmolter

Definitely a shot alternator. This happened to my s55. I was driving down the road and the command shut off. Then the abc and traction control freaked out. After another minute or so of trying to make it to a parking lot the car started getting stuck in gears. Eventually I rolled to a stop with the engine shutting off. Suck in the Middle of an intersection without even enough power to run my hazards and a 4300 pound car to push.