Good evening all.
After an amazing first experience with LiFePo4 starter batteries in my other car, I bought one for the Benz as its battery was far beyond gone (7-9 volts in the morning). The one relevant piece of information here is that LiFePo4 batteries run at a slightly higher voltage - in the 13-13.5V range as opposed to the 12-13V range that regular SLA like to hang around at. I believe, because of this, I'm receiving the message on my dashboard "Malfunction electrical consumers switched off," and along with it goes the defroster, heated seats, 12V outlets, higher HVAC speeds, etc.

I frequently got this message with my old battery as I would be getting my car started with as little as 9.5-10 volts sometimes, and of course it wasn't happy about that - but after it charged up, the message of course went away. I've noticed that I also get this message when I start the car before unplugging my battery charger - so I assume there is some over voltage protection going on here, where the car probably doesn't expect to see 12+V when the starter motor is actually turning. This LiFePo4 battery has 1000CCA and the starter absolutely loves it, straight to life; it doesn't drop below 13V while starting. So, my questions are, is anyone familiar with this apparent "overvoltage" protection or does anyone have documents that show exactly in what circumstances the power saving modes are activated? Because my car is certainly not undervolted - I don't think it's dropped below 13V a single time since the installation of the new battery. What throws me off is the alternator puts out over 14V so this shouldn't be a problem. I've driven 50 miles so far and the message persists. Although, it has downgraded from the more aggressive profile to the more lenient one where it will let some feature consumers run, but not all of them.

 

Have you scanned the vehicle for stored/current DTC errors?

 

No generic codes. But I don't have a mercedes specific scanner.

 

Seems like the problem has resolved itself, no malfunction message today and heated seats worked right off the bat. Maybe it was just getting used to having a fresh battery. 30⁰F this morning and the way it started you would've thought it was 80⁰, love these batteries

 

Unfortunately my warning message has come back a few times. Reading 13.7V engine off and surface charge depleted, 14V+ with alternator going. It's come to my attention that these types of batteries have lower internal resistance, which I wonder could confuse the car's BMS to think it is at a lower state of charge than reality. Does anyone have technical bulletins/information pertaining to the workings of this consumer malfunction warning? It can't be solely voltage based because my AUX battery is also newer. The car is always getting sufficient voltage and amperage. When the message comes up while driving I can tell my car has plenty sufficient voltage by the brightness of the headlights and the snappiness of the dashboard menu, also fires right back up.

 

The search feature in the forum is your friend, but here is a few of the threads discussing the auxiliary battery mal function message:
Light reading , and I missed some.

https://mbworld.org/forums/e-class-w...ml#post8321970

https://mbworld.org/forums/e-class-w...ml#post8329929

https://mbworld.org/forums/e-class-w...ml#post8568736

https://mbworld.org/forums/e-class-w...ml#post8394415

Update: apologies.. I had my mind on the W212.. Different issue for the W211

 

You've basically created your own monster by putting the wrong battery in. Different charging profile and the car expects different behaviors. Basically it doesn't like what it sees. You'd just be better off with a standard AGM battery. You also have a battery control module in there and the battery low voltage tends to kick in when voltage is below 11 then certain items are switched off. Whatever values the car is used to seeing, it's not seeing those. I wouldn't waste money trying to diagnose it, just put in the right battery. You probably can't code it and if you could, it's probably not worth the cost of a $600-$1000 Star/Xentry system. My 2008 still has the original AGM battery too and no issues with it roaring to life when I start it and it's 15 years old at this point. Oh, and I'd also charge up the aux battery. I believe someone mentioned a while ago that it only charges for 20-30 minutes when you start it up and then it stops. Have to stop/start it again before it will charge again. Could also be battery control module.

 

I agree, you're probably right. I want to tame that monster.
I need to figure out what discrepancy exists that the car isn't a fan of, and see if I can solve that. There's DC-DC chargers, voltage regulators, et al electrical shenanigans that I could involve, but need someone to guide me in the right path... exactly WHY the car isn't happy. Because it certainly isn't low voltage, and the dozens of pages I've read on this issue only discuss low voltage and alternator issues. I can't find any technical information on the fault.

 

That's seriously impressive, by the way--hats off. Never in my life I've heard of an SLA lasting that long. Considering that probably comes with a 3-5 year warranty, ponder the potential lifespan on a well maintained lithium battery with an 11 year warranty and 5X the cycling capabilities.

 

Well good luck, I don't think anyone else has done it so not sure if it's in there that you can make that change with just Star or would a few other things need to be changed. Not really worth it on a 2003 model where the value isn't that high to begin with. You only have about 4 years left on the extended 25 year warranty on the SBC brakes.

I'm in a colder climate and the battery in the trunk keeps the heat out. The capacity is also low, charged it up a couple years ago and couldn't get it up to 12.7 volts. As I recall, it probably had about 85% of original capacity based on the max voltage I could get. But those H8 batteries are probably oversized. I stopped sitting in the car with the seat heater on and listening to the radio when I shut it off so I don't drain the battery down when it's not running. I should probably just change it, but I have a 2nd car so won't really get stranded if it doesn't start one day, just curious how much more life it has.

 

Well, the malfunction has gone away for awhile again. I'm going to get a wireless shunt so I can monitor the voltage while I'm driving.

 

You can monitor the voltage in the cluster while driving instead of looking at temperature, or other setting you have by default.

 

And the short answer to the above if you don't want to watch the video is to switch to the temperature display and hit the reset button 3 times with the car in the on position but without the engine running.