skippert

Red Screen on dash with battery symbol, no cruise but everything else seems to be working. Relay? All fuses seem to be good.

wjcandee

Do you have a version with the Sensotronic Brakes? If so, you have an AUX battery under the hood on the upper left side under the air filter cover. When that needs replacement, you get the battery message (and also if your main batt is going, but if you haven't got any other messages, it's likely the AUX). There are threads on here about how to replace it yourself. The cheapest, best option, in my view, is the one I used.

Get this battery from Amazon, fill it, charge it, and install it.


A truly-great AGM battery from one of the top manufacturers, which is an exact replacement. Problem solved. The instructions on how to install it are in various threads on here, and also in the Amazon review I wrote, which is flagged as one of the more "helpful" ones, so it's not too far down the review list. Number 4 right now. Notice that you have to click on "read more" to see the whole review; it's pretty detailed.

I wouldn't buy it from one of the "marketplace" sellers, who sometimes substitute a knockoff YUASA battery or a non-YUASA battery. Make sure the merchant is Amazon.com. Right now, Amazon is listed as a merchant in the right-side panel of the listing. That's a good price, a lot cheaper than your dealer will want.

If you don't have a charger, this one is excellent:

OR this one:
2/5/10 is enough, but 2/6/10 or 3/6/12 is fine, too. I would charge the YUASA on the "2" setting if you have time, but they will let you charge it on 6, but no more.

Come on back with any questions.

clvincent

i would do some more research on this

my red battery light came on and it ended up being the battery control module, not either battery
this is a dealer only/or indie with star item because it has to be programmed by star

hopefully yours is just the aux or big battery
but it can be other things

wjcandee

The likelihood that it is the BCM -- which isn't a wear part -- is much lower than that it is simply a battery.

You can take the car to any Advance Auto Parts and they will test the batteries for free with their Midtronics tester, the one that MB recommends be used to test an AGM battery (which both OE parts are). Advance has an excellent big battery, it's their H8 (Group 49) Platinum battery, which is an AGM battery. If that's defective, their battery is as good as any. If it's the AUX battery, the one that Advance sells in the proper size is not an AGM battery. It will fit. It will work. But I thnk you really do want an AGM battery in that application because AGM batteries don't vent noxious gas (and it is located by the air intake for the filter) and can handle being tilted, jostled, etc. better than non-AGM batteries because there is no circulating fluid.

I would let them test both batteries and not feel guilty if I buy the AUX somewhere else, on the theory that I would buy the big one from them when/if it is defective. They also install for free. IF you still feel guilty, buy some wipers from them or something (they put those on for free too).

bbirdwell

Or you can monitor the health of your batteries yourself using a Solar BA-5 or its more capable brethen:

http://www.amazon.com/BA5-100-1200-C...rds=solar+ba-5

I check both batteries and log the cranking amps into my maintenance manual whenever I change the oil or perform other maintenance.

burgca

bbirdwell, great idea to monitor the batteries, definetly beats waiting for a jump start!!

repguns

So, replaced the main battery but not the aux in front. Main battery is drained after sitting overnigt. would the aux battery cause this? I am about to bring it to an indy with a star to see if they can find out the cause.

cmriv

If you battery drained over one night, you have and electrical consumer staying on. AKA a draw on your battery system. You need to do a battery draw test to see how big of a draw it is and at the point refer to DAS to decipher which module or modules aren't going asleep.