plan on little over 1 month vacation oversea.
Car currently park in the garage which maybe be around high 30 degree.
Should I disconnect the battery from the trunk?
if so, should I just disconnect one terminal? (positive) or (negative)?

thanks,

yes disconnecting the battery terminal would be best. disconnect the negative terminal
is the safest.

also I would tape up the cable with some black tape.

thanks for the advice!

Is it an SBC car? The car would have a second small battery at the engine bay. This small one is intended for a backup for the SBC brakes, not sure if it would drain more when the boot battery is disconnected.

It is equipped w/ SBC.

Anyone recommend otherwise?

Take a look at the other thread about battery chargers. I would suggest simply putting a BatteryMinder on each battery (you can use one of the bigger ones and connect it in parallel to both).

For a long time (2 months or more, I would also disconnect the battery).

Even if you disconnect the battery, it would be best for the life of the battery to put a float charger on it.

I don't think I can get either one on time, as I will be leaving in 2 days.
Can you suggest something "easier"?

Well this the official Mercedes Procedure for removing the battery, Document No: AR54.10-P-0003T

On vehicles without code (889)Keyless go
1.1 Switch off the ignition and remove the
transmitter key from the EIS control unit

On vehicles with code (889) Keyless go
1.2 Switch off ignition and remove transmitter key
from the transmitter range of the vehicle

2 Remove trunk floor covering from trunk.
3 Remove spare wheel cover or spare wheel well trim panel from trunk.
Depending on equipment.
4 Loosen nut and remove ground line from the battery

Install in the reverse order
5 Perform basic programming
6 Read out fault memory and erase if required On vehicles up to 29.1.04
7 Connect STAR DIAGNOSIS and read out fault memory

But this is "just" the guide how to remove the battery. It isn't talking about leaving the car not used for a long period. This is for the service work, servicing the car when the battery needs to be disconnected, or when the battery needs to be changed.

Did you find any guidance for the actual case of leaving the car parked for a long time?

You'll be very sorry if you disconnect the battery.

First thing you'll be doing afterward is going to dealer for lots of system resetting.

Your dealer sells a battery charger that's safe to leave connected for long periods. It will be cheaper in the long run in all liklihood.

okay, you just make me pee on my pants.
are you serious?

if you disconnect the battery the stuff you may need to reseted are the sunroof and windows and those can be done your self. remember if you put your car in long term storage don't always have access to wall power outlet. disconnecting the main battery is a must to protect the battery for draining down.

That's good news, those windows, seat, sun roof I have no problem reset them myself

Don't disconnect the battery, otherwise it'll be troublesome and when you get back from holiday, all the electronics will be acting up.

My suggestion is, if you leave your car in a garage, don't lock it. Just leave it unlock so the battery won't be drained to monitor your Alarm for 1 month.

I left my car for 2 months, but when I go back, the car started up like a champ.

Anyway, my suggestion could be wrong, but it works on me so far.

What kind of electronics will be acting up? ( leave it unlock is not an option for me. )

All the above are stated in the car manual but you also have to normalise the steering sensor, turn from one end to the other a couple of times. This clears a few malfunction indicators.

Wouldn't it be sufficient to remove the alarm fuse(s) to get rid of that current drain?

On the other hand, if the battery is OK, it must survive a month if MotorWerkz had no problems after two months.

I can't imagine. My friend's BMW E60 was a nightmare after he did that, all the sensors are not working, his xenon is only working on the left one and many more.

You just don't want to take this route, maybe you can manually lock your car so the Alarm doesn't have to be activated.

hmm... how do I "de-activate" my alarm?

manually dead lock the trunk first.
"unlock" my car.
Get into the cabin, manually push down the door-lock-pin and exit out from the passenger side?

But wait? I thought MB will active alarm if the car is unattended for several min? (or is it just my brother's Lexus?)

hey dude,

dont stress your self out. have fun on your vacation or what ever you will be doing.

yes these cars have electronics that are very sensitive to voltage. that was the main problem with the some of the early 211s. which was address with replace voltage regulator, SAM, etc.

and Yes a trickle charger would be the best option, however you have to have it plugged up to a outlet.

if you leave the car battery connect a month while you are away. the worst could happen is the you may need a jump start.

remember the main reason for disconnect the battery is to protect the battery for damage due to full discharge. therefore, if you disconnect the main battery you would not have to worry about jump starting. However, you have to deal with a few electrical malfunctions that will pop up due to lost of battery that last thing the system remember is losing voltage. the car is not smart enough to know that you was disconnected that battery. it just see a sharp voltage down and start trying to shutdown systems for protection. most of the of the malfunctions will clear it self up when the system realize that the voltage is Okay.

Thanks~~~ I will enjoy my vacation.