Trickle Charge Battery From Trunk, Options?
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From: Chicago
CLS55, CL63
Trickle Charge Battery From Trunk, Options?
All of my other cars have rear batteries but this one has the MB single battery system (under dash and hood, no trunk battery) and the front trickle charging is crimping my style. I can charge via the cigarette lighter in the trunk but it's switched so only works when ignition is on. On my c219 I can swap some fuses and get always-on cigarette power if I want. Is this an option on w221?
All of my other cars have rear batteries but this one has the MB single battery system (under dash and hood, no trunk battery) and the front trickle charging is crimping my style. I can charge via the cigarette lighter in the trunk but it's switched so only works when ignition is on. On my c219 I can swap some fuses and get always-on cigarette power if I want. Is this an option on w221?
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Someone is going to complain you connecting ground to the battery pole instead of chassis ground. I'd say either way is fine because this is a maintenance charger and only charges the battery when the car is parked. In this case the car is not monitoring battery charging via the sensor at the ground pole anyway.
Someone is going to complain you connecting ground to the battery pole instead of chassis ground. I'd say either way is fine because this is a maintenance charger and only charges the battery when the car is parked. In this case the car is not monitoring battery charging via the sensor at the ground pole anyway.
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04 E55 AMG (totaled), 07 S550 4Matic, 14 E63S
I would think the starting battery would be good for a long time if it was fully charged before being parked. Isn't it isolated from the rest of the car precisely to avoid it becoming discharged and the car not starting?
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On a pre-facelift W221 indeed no need to have a maintenance charger on the starter battery (easily survives 6+ months). The idle current is drawn from the consumer battery.
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1983 Nissan Shltbox
Someone is going to complain you connecting ground to the battery pole instead of chassis ground. I'd say either way is fine because this is a maintenance charger and only charges the battery when the car is parked. In this case the car is not monitoring battery charging via the sensor at the ground pole anyway.
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See B95 on the diagram. B95 is the small sensor attached to the battery negative pole. The battery ground wire is not connected to the negative pole but the B95 sensor.
EDIT: having a second look after the comment from kevm14, the diagram has a constraint telling the ground side sensor is installed only on specific models, pre-facelift and facelift.
Last edited by Diesel Benz; Jan 27, 2022 at 09:58 AM.
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04 E55 AMG (totaled), 07 S550 4Matic, 14 E63S
I can tell you the rear battery on a pre-facelift W221 is grounded directly to the body. However it looks like the positive cable comes from some module and I'm not sure what that module is. But since it's on the + side, I would just connect a charger directly to the posts, for the rear battery, since there is no ground side monitoring.
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1983 Nissan Shltbox
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From: Ontario, Canada
2014 E350, 1989 560sl, prior 2001 E320, 2008 E300
Trickle Charger in Trunk
I have used a trickle charger on the trunk battery of my 1989 560SL for a few years now and it seems to work fine. I even installed the extension that Kent Bergstrom demonstrated on the Mercedessource.com website. It made it easy to connect without having to open the battery box.
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From: Atlanta GA
2012 E350 Cabriolet now SOLD to my son
Well those pics do show some sort of module, esp the ones from FCP Euro. So maybe some models have that little module. So do you connect to the post then bypassing /avoiding the module? would that even work?
