mbdiesel12

The original MB battery in my 2012 E350 BT is now going on 5 years old. I want to have it checked but if it needs replacement what's the process?

Do I need to supply a 12v charge across the + and - jumper posts to keep my settings after removing the battery?

If I do that the battery cables will then be charged and I risk shorting the electrical system during installation. Is that correct? How do you prevent that?

Any recommendations on a good battery. Mine is 800 CCA.

kajtek1

If it ain't broken - don't fix it.
Testing batteries is a whole science.
Beside new-technology gizmos you can do load test.
The easiest is display car voltage without starting the engine, then turn all the headlights and blower on. Voltage drop will give you INDICATION about battery condition.
Other test would be - when at home - start/stop the engine several times in the row.
If the battery let you crank the engine for couple of minutes -it should last for a while.
Recharge the battery after the test.

mbdiesel12

No offense but that seems a little too much like checking for land mines with your feet!

I think I'll have it load tested to determine the percentage of battery life remaining.

I'd rather replace it on my terms than wait for a cold, rainy night on the road somewhere. Just want to be a little more proactive.

Carsy

My original Varta 70 amp hour Absorbed Glass Mat battery will be 10 years old in October (car build date).

Yours may be only at half life.

mbdiesel12

That would be nice. The dealer wants $400-$500 to replace. Not that I'd have them do it. I'd replace it myself with an Interstate AGM for around $270 or so.

I just wanted to know how to avoid losing my settings. I don't know if those cig lighter 12v battery savers work or not. I guess it depends if the cig lighter circuit is live with the ignition switch off. I'd have to check.

rapidoxidation

While Kaji's post made me chuckle and vow to not let him ever touch my car with his tools, he does have a good point about using the car's voltmeter to check battery condition. Get the VM showing on the dash display then turn the car to "on" to get the glows lit up. Observe the voltage. Turn the key to "start". Observe the voltage. If you're dropping into the single digits, that's bad. In my opinion. Other than that, I'd not sweat over a 5 year old battery unless I knew it had been abused (drained to zero more than once or twice).

Batteriesplus.com shows your battery (850CCA Duracell) for about $220. Easy job to change, and as far as "settings" goes it'll take about 5 minutes to restore what was there prior to swapping it out.
https://www.batteriesplus.com/batter...iesel_optional
They'll even give you 10% off if you buy it online and pick it up in the store.
Not affiliated with B+ but I have used their batteries in my trucks, cars, and motorcycles with happy endings. Got 'em in my Benz and Ducati right now.

Edit: If your ciggy lighter is fused like my '05, there's a 2 position fuse that energizes it. In one position, it is hot all the time. In the other position, it is hot only when the car is on. Your owner's manual will tell you where the fuse is, and looking at the fuse will show you if there is an A/B position.

mbdiesel12

Thanks for the info. I don't know if my car has the voltmeter display or not but I have a multimeter that will work. Also, my radar detector shows a voltage readout and I know the car is charging at 14.x volts so the charging system is good. I think I need a battery draw test with the proper equipment to really know if the draw capacity is there. I'm having it checked today.

Regarding settings, my main concern was losing the electrical connection during the battery install process and having the car go into limp home mode or something stupid like that.

kajtek1

Don't panic. No car will go into limp after battery disconnect.
Your model is W212 body, so go to section to check what needs to be reset.
Most likely steering sensor and windows.

mbdiesel12

Thanks. I figured that but you never know about radio lockout, etc. Some guys with other makes complain of having to go to the dealer to get things reset or have their radio codes restored.

My battery tested 9.6v at cranking with 400A load so it's at the bottom end of acceptable. The day it was tested was cold and rainy but the cranking test didn't account for temperature.

I'm OK for the time being but will replace the battery in the next month. I can keep an eye on it with my multimeter by using the min/max function. Don't need to put another load on the battery at this point. Can't complain about it lasting five years.

kajtek1

Last radio I have seen installed in MB was on 2003 model.
Newer cars have command center that is hard-coded to the car by SD and you don't loose the code.
How did you measure 400 amp?

mbdiesel12

The independent MB tech that did the load test set his load tester for 400A. They usually set the rate at about 50% of the battery rated CCA.

kajtek1

So it was static load?
I understood it was engine cranking load.

SEC1939

my battery on my 2005 E CDI was original when I sold it last summer with 225,000 miles. These monsters last a long time

kurtismayfield

I got ten years out of my original battery. Replaced with Auto craft H8. [Advanced Auto]


Free installation and they use a settings saver via the cigarette lighter.


Couldn't be easier.


Good luck