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Since we got our (used) 2011 E350 in 2014, we have had to plug in the battery to a charger every other night. For short trips, the battery only restores to 57%. It's not our new battery, it's the way the car thinks about recharging the battery. Anyone else have to do this? Is there a remedy? You might wonder why we do this: I got stranded one day with an uncharged battery. It's not inconvenient to hook it up in our garage. What do people in cold climates do when battery power is important for cold starting if they have this model?
IIRC there's a networking signal cable plugged into the alternator. Unplug it.
But I'm sure someone else will chime in soon. There's a pretty big thread on the subject here in this subforum, likely on this page or the next one.
Your E-Class chassis has multiple ways to work a low battery condition. Floating or disconnecting your unused batteries is a great practice to extend good service life.
Low Batt causes :
1- By wild SAM modules draining battery during engine off
2- By any of you car module being swamped to disrupt COM's.
3- By users listening to audio for extended time with engine off.
4- By battery being sulfated or too old.
5- By the buggy ECU controlling the alternator to go deep low putting a short on both batteries or letting output float free.
At no time during engine runtime, the battery current should become heavily negative for extended periods.
Dont jump to conclusions:
You need to identify what issue is calling your attention.
Replacing another battery may not be what's needed to power up your car reliably.
On the flip side a new $200 AGM battery works like a capacitor to supply instant high-load demands like starter or spark coils or 100A fan...
Last edited by CaliBenzDriver; Oct 26, 2022 at 02:35 AM.
Please elaborate : For short trips, the battery only restores to 57%.
Where does the 57% comes from ? Those battery tester unit capable of reading state of charge ?
If you have a GoPro camera or similar which you can record Battery Voltage and Amperage ( engineering mode ) at the instrument cluster, do so from before engine start to after engine stop, the short trip you mentioned.
I worry there could also be parasitic drain somehwere on the car from aftermarket item installed.
Example, my OBD2 based engine monitoring + logging system and special headlight-high beam interface, has stand by current this much, below.
I do still charge my car battery once per week due to the 6.3 amps lost per week, if I do not use the car at all.
Charging battery is also a must after every car washing I do myself ( 3 hours ) because I open doors a lot.
My car has the single wire connector to alternator ( small data wire, LIN ) disconnected, if your connector to alternator uses only single wire LIN, that means your alternator is getting the STUPID charging algo
manipulated by the ECM. If you disconnect that single wire LIN connector , the smart enough alternator built-in charge controller will do its job without any dumb-azz algo inteference from the ECM.
There then you will enjoy what a proper charging should be like ...like super smooth no-YoYo 14.1 Volt and super low 0.5 to 1 amp of charging when battery is already full.
I thought my 2014 facelift is stupid for its charging algo, but when I saw my friend's C200 W204 of 2010, it is TOTALLY IDIOT algo and annual or 18 months max battery replacement is what my friend had to do.
I disconnected his alternator LIN cable too for a year now. So far so good, just like on my car.
Last edited by S-Prihadi; Oct 26, 2022 at 07:05 AM.
Reason: typo correction
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