spongebob

I just find out that the battery is actually located in the trunk, why is that?

lorinserbenz

Safety and weight distribution...

scorchie

Primarily because there's no room for it in the engine compartment. Moving it to the trunk obviously has its benefits and bad points, but for the size battery that the W211 requires, it really has to be in the trunk.

Mercedes does not put the batteries in the trunk on all the cars, so the criteria must be something design related rather than one that is really important.

And, you do have a battery in the engine compartment, it's a 12AH battery so it is only about 1/4-1/6th the size of the battery in the trunk.

-s-

W211 Ryda

If I can recall correctly, there are 2 batteries. The one located in the trunk is the main battery, and I think there is one located in the engine compartment acting as a reserve.

SAguirre

There is also a small lead-acid-gel battery in the front engine compartment for the SBC system. The big on in the trunk is for the rest of the car.

It is not unusual for Mercedes and BMW to put the batteries in the trunk. Since they avoid the engine heat, they tend to last much longer. I have never gotten less than 5 years out of any MB battery. I think that the W210 has the battery under the back seat.

Steve

benzboy

Correct, the 210's battery is under the back seat. The 211 battery is a big devil, hense the trunk location.

deuce zer0

the 210's are a pain in the a$$. anytime i needed to get to the battery...everyone is always like, what the hell are you doing taking out your back seat!?

scorchie

If you don't have any tools, or if you have things in your trunk, the battery under the seat is easier to get to than the one in the trunk. Plus, the W210 had the jumper terminals under the hood.

-s-

deuce zer0

i thought i had seen those once. isnt it just one little stud for the red side of the cables?

vraa

For the black side. The black is the grounding point.

scorchie

Yes, one for the red side. The black side goes to a ground, like somewhere on the engine or accessory bracket.

-s-

SAguirre

I thought that the W210 had a remote terminal for starting it! I guess I was right. I asked when I bought my W211 and they said that it also had it, but I never saw it. Why did they get rid of the remote terminals? The way that the access to the spare tire and battery is designed on the W211 is very bad!!!!

I just finally bought an "onboard battery maintainer" so that I won't have to constantly open the darn thing. With this maintainer, I just have a little (regular 120V) plug sticking out where the side mesh is in the trunk. Then when I park it for a while I plug it in really easily. I have always gotten great life out of batteries in my MBs, but it might be that I always keep a maintainer hooked up if the car will sit for one week or longer. My car tends to sit a bit.

Steve

konigstiger

Offhand, does anyone the average cost for batteries (engine & trunk) on the 211?

scorchie

The W211 does not have jumper terminals. My US manual states that jumping must be done directly on the battery.

A trickle charger should not be used on the W211 while the battery is connected to the car. It is unlikely that it will damage the BCM, but it does tend to freak it out. On the W203, it is likely that damage will occur to the BCM if the battery is charged (high speed).

-s-

scorchie

List prices as of this date:

95AH, Varta, $240
95AH, Hoppecke, $272

70AH, Hoppecke, $218

12AH, forgot who makes it but maybe Varta, $127

-s-

konigstiger

Thanks.

SAguirre

I inquired about this at my dealer. They said that as long as it was not constantly charging (to the point of overcharging) it would be fine. The main battery so big that it acts as ballast and the system does not notice if 2 amps are being delivered to the battery. This battery maintainer is only a 1.5 amp maximum charge and it totally turns itself off when the battery is fully charged. It goes into float mode.

My car has been hooked up with either my older "smart solid-state" charger or with this maintainer for weeks at a time and I have not had any problems or weird issues. I will ask the head mechanic about this (just to be sure). But I heard that disconnecting the battery is a lot more problematic for the car, not to mention that it would be moronic for me to do that all the time.

Thanks for the input though, I have heard about issues before and it is good to know about the possible problems.

Steve

scorchie

Disconnecting the battery IS problematic, but it doesn't damage the car... just requires a lot of reprogramming. And you're right, that would be silly to do just to keep the battery maintained. Maybe your secondary battery should keep the programming while the main battery is disconnected.

Charging the battery in the car can damage electronics, so it's preferable to do that. There's also the issue with gases, etc. Take a look at your owner's manual.

If your shop says it is OK, you may want to get that documented!

-s-

pa28pilot

One technical nit: It's not a gel cell, both the front and rear batteries are absorbed glass mat (AGM). The upshot of this is that they are more robust and don't require as delicate charge curve as gel cells do. (If you charge a gel cell wrong, you can cause the gelled electrolyte to delaminate from the electrode surfaces.) AGM's are usually non-spillable, and can often be installed in various orientations.

pa28pilot

I remember reading the dire warnings about never connecting any loads directly to the battery where the BCM couldn't track it. It makes sense that the same would hold true for chargers, but:

Is there something special about MB's "Solar Panel Charging Module" (W900 589 02 63 00) that makes it o.k.? In a bulletin (P-I-54.10/116), they indicated that it can be used on W203,209,211,215,220 and 230's. They're even plugging the negative terminal into the cigarette lighter, which surprised me a little.

scorchie

Mercedes calls it "fleece technology"

They generally have a black case to denote the standard Mercedes batteries with a white case.

I have one in my G-class for more resistance to shocks that occur offroad, as you said they are more robust.

-s-

SAguirre

Good suggestion! I will see what I can do about it. If the maintainer does damage something then I will remove it before I take the car to the dealer and play STUPID (sometimes not too hard to do ).

However, pa28pilot brings up a very good point about the solar chargers. I think that the person who I asked mentioned that since the solar one was OK, then a GOOD maintainer "should" also be OK.

Now I am beginning to think that I should remove the maintainer from the car when I get home tonight. Do you have any idea what I should look out for? I mean, aside from error messages and warning lights, what would I notice if the maintainer has caused a problem?

Steve A.