E-Class (W212) 2010 - 2016: E 350, E 550

Best way to charge car battery?

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Old 03-03-2021, 05:53 PM
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I can tell you that when I have not had the car on a trickle charger and not driven for a few weeks my ECO S/S light will generally not illuminate until I have driven for a pretty long distance. On the other hand if I have had the car sitting on the trickle charger for a day or two and head out, the ECO is illuminated and goes green within the first couple miles of driving.
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Old 03-03-2021, 06:57 PM
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Originally Posted by KEY08
I can tell you that when I have not had the car on a trickle charger and not driven for a few weeks my ECO S/S light will generally not illuminate until I have driven for a pretty long distance. On the other hand if I have had the car sitting on the trickle charger for a day or two and head out, the ECO is illuminated and goes green within the first couple miles of driving.
Makes sense, as the priority would be the main battery... so keeping it "maintained" means less time spent charging it once underway, which should correlate to ECO function availability.
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Old 03-04-2021, 11:56 PM
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Originally Posted by ZZGlk
The Aux battery will not charge until the Power Relay tells it to charge, so using a trickle charger on the main won't keep your Aux battery charged.

The Power Relay looks at main battery voltage and aux battery voltage and has a timer that kicks in after about 15-20 minutes of driving, if the voltages meet requirements. That is what connects the Aux battery to the main battery for charging. So, if you don't drive the car, the aux battery will eventually go dead. Only way around that is to specifically charge the Aux battery itself.
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I agree. The Simplest thing to do is to hook your charger to the main battery until it is satisfied and goes into float mode. Then, I take the charger and hook it up to the battery in the trunk. The reason is that electricity doesn't flow from the main battery into the auxiliary battery, unless the SAM (microprocessor that controls all electricity in the car) is activated. AND the SAM is only activated when the car is on and the alternator is running. This made it easy for me to understand why just hooking up the main battery didn't help the little one in the trunk.

Last edited by Alandf; 03-04-2021 at 11:57 PM. Reason: spelling
Old 03-05-2021, 02:27 AM
  #29  
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install a pair of battery tenders, a junior for the aux battery, and a regular size one for the engine battery, and wire them to a single power cord, so you can just plug the car in when its parked in the garage for awhile.

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Old 03-05-2021, 08:58 AM
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Does the W213 still have two separate batteries or did MB go to one battery like every other manufacturer?
edit: I guess the answer is no. There is a voltage converter now in place of the trunk battery.

Last edited by KEY08; 03-05-2021 at 10:43 AM.
Old 03-05-2021, 10:52 AM
  #31  
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Originally Posted by KEY08
Does the W213 still have two separate batteries or did MB go to one battery like every other manufacturer?
edit: I guess the answer is no. There is a voltage converter now in place of the trunk battery.
Is a "Voltage Converter" the same as a "Battery?"

...and, how do you charge a "Voltage Converter?" LOL
Old 03-05-2021, 11:25 AM
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I think it's like a capacitor. Once again, this is just the aux batt not the main battery

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