I re-checked the battery voltage after it warmed up a bit outside. It is now reading closer to 12.6V. The car definitely struggles more on cold mornings after sitting overnight vs a warmer morning. Is this more likely to be a bad battery if there is no parasitic draw?

 

maybe, if you have a meter you should measure what the voltage drop is during cranking.....

 

on the other hand car triggers convenience disable easily if voltage drops, could it be fuel pressure related, not sure how gasoline engine fuel system works

edit: can you test by new battery?

 

Just checked...it was about 11.6 at it's lowest point during cranking. I will try to check it in the AM when it is colder outside. Do you or anyone else know what a cold ambient temperature cranking problem might mean?

 

I haven't had any convenience lights show up since the BCM was replaced, thankfully. I thought of a new battery, too. You think the battery might have been damaged when the poles were reversed?

The w211 does have an extended warranty that was issued by MB to extend the warranty to 15 years/unlimited miles. But would cooler ambient temperature leading to slower start be related to the fuel pump?

 

If battery was just connected wrong poles in car system, I doubt that will damage it, but if battery has drained completely it may not recover again (some 'intelligent' battery chargers has recovery option). Also AGM batteries need higher charge voltage than normal wet batteries.

In diesel engines cold start problem is often fuel pressure related, but gasoline system is fully different... only those secondary air systems have caused problems in gassers but IDK how temp related those problems usually are...

 

Why don't you replace the "new" battery (should still be under warranty)? Of course don't let the idiots at Batteriespluss install the replacement. In addition why aren't you holding the dealers and the independents feet to the fire for not properly diagnosing and correcting the issue? A competent Mercedes dealer or independent service tech should have provided better service than you have received, also I would validate that your Aux and Main battery are the correct voltage and size.

 

The car doesn't draw that much power during a start, unlike old cars, so the "starting slowly" thing seems dubious to me. May just be a perception while your brain is looking for something to be wrong. But if you are sure, why not try CHARGING the battery? Nowhere in this thread to I see you say you charged it. Get a decent intelligent charger like the Schumacher, with a decent-but-not-huge amperage, like this one I have: http://www.walmart.com/ip/Schumacher...arger/15140195

Set it on the medium setting and charge the thing until the charger says it's full. Could be several hours. I occasionally "top off" the batteries in our ML350 and E500. It can't hurt your battery life and may eliminate your symptoms. Most battery replacers say they have "fully charged' the battery before installation, but that's usually not true, and your alternator isn't usually goimg to apply a current long enough to fully charge a half-discharged battery unless you are taking long, long drives. Most people are driving around with batteries that aren't fully charged because they seem to "work".

Next battery, I would avoid B-plus and get one of the ones that we have recommended on here. For a while, Amazon had a great deal on an AC/Delco, but now its price has gone up. Advance Auto Parts has a great AGM platium one that you can usually get a great deal on if your order online and pick it up (and most will put it in properly for you, but there is no reason whatsoever not to just install it yourself).

Good luck!

 

Thank you, everyone, for your responses. I finally gave up and decided to take it to Mercedes and make sure there wasn't something else wrong that I was missing (so far, BatteriesPlus, to their credit, has agreed to pay for all the damages, totaling as of right now over $1800, so, if something else was still wrong, I wanted to know sooner than later to try and get reimbursed). It definitely was starting much more slowly than it had in the past; a couple of times it took about 3-4 seconds after turning the key before the car actually turned over. I've never had that before.

They couldn't find a single thing wrong, which is, I guess, good and bad news. They recommended buying a Mercedes battery, because they have seen in the past where third party batteries just don't function like a Mercedes battery (go figure...everything with Mercedes is proprietary). They even let it sit overnight and couldn't find anything that would be causing it to start slowly. I bought the battery from the parts department and installed it myself. I bought the battery a couple of days ago and didn't get around to installing it til tonight. Interestingly, the convenience functions light came back on again yesterday with the BatteriesPlus battery, and the functions were actually unavailable (prior to the BCM being replaced, it would say they were unavailable, yet still be available). After changing the battery out, everything is back to normal. Will see how it starts in the AM...should be cold tomorrow morning, so hoping that if I'm going to see any starting problems, it'll show up tomorrow or not at all.

Interestingly, the battery from Mercedes has a lower charge than the BatteriesPlus battery (12.3V vs 12.4-12.5V). Practically speaking, not sure this is much of a difference.

Thanks again; will let you all know if I have any more problems.

 

So, new battery from Mercedes appears to have a low charge. When I bought it, it had a charge of about 12.2V. On one cold morning, it had a reading of 12V. I bought the Shumacher battery charger, charged it up, and next day it was down to 12.3V. Should I take it back to the dealer and get a new one?

 

Those voltage charts are also based on temperature, between 12.5-12.7 volts at around 70 degrees, the colder it is, the lower the voltage. Also those state of charge charts refer to a battery at rest with no load on them for several hours. When you have the battery hooked up to the car, there's always a small load on them as the car takes a little power to maintain certain settings. The real key would be the date code on the battery, usually either a letter code or number to indicate month and the year. If they sold you one that was 3-6 months old or more, maybe it'd make sense to demand one made in the last month or so.

 

Testing batteries is pretty tricky even if you have load tester.
Still battery showing 12V in the morning would not turn the engine, so I would wonder about reading accuracy.
drew is not showing the location, but in US most of automotive suppliers will hook up battery to computerized tester for free.

 

The battery low warning message doesn't kick in until the voltage is down to 11 volts. Mine will read as low as 11.5 volts on cold mornings, normally it's around 11.9 and it still starts fine at all voltages. Then again, mine is over 7 years old.

 

You are likely talking about car voltage displayed on the cluster, not about actual battery voltage?

 

Thank you, everyone. Yes, that's correct, it's the voltage on the cluster, but my multimeter usually reads only 1/10 of a volt higher than the cluster. The interesting thing is, the battery from BatteriesPlus never read as low as this one from Benz has.

 

I did not confirm it on W211 yet, but on W210 the car voltage was always 0.5v lower than battery voltage.
Battery showing 11.5V static will not start the engine. Trust me on this one.

 

maybe your starter is starting to fail.....

 

If "Batteries Plus" screwed up by even touching the terminals the wrong way, they owe you for the ENTIRE repair.


And probably some coverage for any latent failures that show up over the next year.

 

Yeah, but, it only seems to happen in cooler weather. Would cooler weather affect the starter?

So far, BatteriesPlus has paid everything ($1800 worth). I'm hoping that's the end of the problems due to the pole reversal, but...

On Thursday morning, I went out to start the car, and the right low beam headlight was out. I also found that the fog light was flickering on and off (very sporadically...comes on for a second and goes off for a three seconds, comes on for a second, may not come back on for 10 seconds, etc). The smaller light next to the main headlight works, the bright light works, the outer marker light works, the turn signal works, it's just the low beam that doesn't work and the fog light that flickers (all on the right side). Left side works fine. Checked the fuse, looks fine, even switched it out with another fuse to make sure. It is odd that it all of the sudden stopped working.

Any ideas?

 

Bet it is the front SAM

 

I have the same feeling that it's the SAM...it doesn't make sense that it would be anything else. If it was a loose wire, the fog light would flicker while driving (going over bumpy roads), rather than just sitting idle.

I don't totally understand why the poles being reversed is just now causing things to show up in the front SAM. I know the damage was done when the poles were reversed, but why didn't it show any symptoms immediately (like the rear SAM did)?

 

Microprocessors can suffer latent damage from surges and reverse polarity.

 

Before jumping on SAM, I would check the ground in this corner.

 

Thank you, both. Is this the ground on the wheel well? It looked intact to me the other day.

Today, I had an ESP malfunction light come on while driving (not the red stop sign one, just a white one that said refer to owner's manual or something like that; brakes and everything else appeared to work ok). It went away after I shut the car off and turned it back on a few hours later.