rapidoxidation

should I disconnect the batteries (main and aux), connect a battery maintainer to the main battery, or simply walk away?

kajtek1

Walk away. Month is nothing.
We had our W210 and W163 left for 5 weeks with alarms on and they always started on their power.
If you don't have problem with your car going to sleep and I hear lot of owners do - even not noticing it, your battery suppose to be fine.
Observe interior lights and cluster going out in 5-10 seconds after closing the door.
That said, pulling the clamp on battery will be good insurance against several things. All you will have to do after is windows and sunroof calibration, what is not a big deal. From my memory W211 doesn't need steering calibration, but even if - not a big deal.
Battery with clamp off will hold the charge for at least 6 months.

rapidoxidation

Given that it'll be in my own driveway (in other words, it isn't a big deal if it is dead in a month) I think I'll do just that and walk away. Testing under controlled conditions, and all that. Gotta know what the car can and won't do.
Thanks for your response!

Of course, the UNcontrolled condition is that I'll be riding to the airport in my friend's '04 E500 and IT will be sitting for a month as well. Worst case is AAA gets a phone call on 31 November...

kajtek1

Bare in mind that I left my cars in dry weather. If you leave them in damp conditions - the parastatic drain will get much bigger.
I takes just seconds to disconnect battery clamp on both cars and have no more worry.I would not worry about aux battery.
Last time we called AAA - they took over an hour to arrive and that was in the city.

Yuille36

Connect the battery maintainer and have peace of mind.

kajtek1

Battery maintainers are good and HF still sells them for 6 bucks, but just like anything they add 1 more item that can fail.
Over the years, having lot of batteries from RV and boats, I had 2 of them killed by maintainer. Beside, no power to use them at airport.
Pulling the clamp is bulletproof.

cetialpha5

I would just connect a low amp charger to it after a month, anything less than 10 amps should be fine. There are also stories of battery maintainers going bad and they end up frying your battery when it's unattended and connected all the time. A 10 amp or less charger should have it charged up in less than a day.

F1Fan

Do you have airmatic? This will be a good test to see if it leaks!

rapidoxidation

Just back from the trip yesterday. The car has been sitting in the driveway since I left, no battery tender and battery stayed connected, with the car getting rained and snowed on. In fact, it was under several inches of snow when I took the key from the kitchen hook and climbed in to fire it up this morning. Started up like it had just been turned off yesterday.

I surely do like this car.

Strigoi

That's not that much time. My E63 has sat for a month or more in the garage and has no issues starting. It's currently been about 3 weeks since I last drove it and the only reason it's going to move before it's getting sold is to get a smog done and for pics.

ot1

kajtek1

Not anymore. Its been few years already when they changed the policy that free MB roadside assistance apply only when you $$$pend some money at dealers.
The assistance doesn't have tow trucks anyway, so if you need towing, you need to call different service anyway.