W212 Battery voltage low advice
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Joined: May 2024
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E class W212 E250
W212 Battery voltage low advice
Hello everyone again, I have posted here a while back asking about what could be the problem with not cranking of the car. I found out that my battery reads 11.50 Volts.
Now I know that is low and it won't start the car, but the car won't even crank. Is the car itself not cranking because of the voltage? Nevertheless, I need to charge it, but I am currently away from my home, so I don't have too many resources to use. For now I only have a battery jumper pack that has starting amp of 150 and peak amp of 500. The car battery has 800CCA.
What could I do in this situation? Would the jumper pack be able to get the volts enough for the car to start? If so, how long should I leave it on for charge?
I am not really sure what to do in this scenario, so I would be grateful for any advice you guys could give.
For context, it is an E250, 2013 model.
Thank you very much.
Now I know that is low and it won't start the car, but the car won't even crank. Is the car itself not cranking because of the voltage? Nevertheless, I need to charge it, but I am currently away from my home, so I don't have too many resources to use. For now I only have a battery jumper pack that has starting amp of 150 and peak amp of 500. The car battery has 800CCA.
What could I do in this situation? Would the jumper pack be able to get the volts enough for the car to start? If so, how long should I leave it on for charge?
I am not really sure what to do in this scenario, so I would be grateful for any advice you guys could give.
For context, it is an E250, 2013 model.
Thank you very much.
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Joined: Oct 2010
Posts: 5,141
Likes: 1,293
From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
Hello everyone again, I have posted here a while back asking about what could be the problem with not cranking of the car. I found out that my battery reads 11.50 Volts.
Now I know that is low and it won't start the car, but the car won't even crank. Is the car itself not cranking because of the voltage? Nevertheless, I need to charge it, but I am currently away from my home, so I don't have too many resources to use. For now I only have a battery jumper pack that has starting amp of 150 and peak amp of 500. The car battery has 800CCA.
What could I do in this situation? Would the jumper pack be able to get the volts enough for the car to start? If so, how long should I leave it on for charge?
I am not really sure what to do in this scenario, so I would be grateful for any advice you guys could give.
For context, it is an E250, 2013 model.
Thank you very much.
Now I know that is low and it won't start the car, but the car won't even crank. Is the car itself not cranking because of the voltage? Nevertheless, I need to charge it, but I am currently away from my home, so I don't have too many resources to use. For now I only have a battery jumper pack that has starting amp of 150 and peak amp of 500. The car battery has 800CCA.
What could I do in this situation? Would the jumper pack be able to get the volts enough for the car to start? If so, how long should I leave it on for charge?
I am not really sure what to do in this scenario, so I would be grateful for any advice you guys could give.
For context, it is an E250, 2013 model.
Thank you very much.
If your car does not even try to crank then as the first troubleshooting step I would check if the start solenoid at the starter motor gets the 12V "signal" when you try to start. If signal is there but no crank then your starter motor solenoid is bad and you need to replace the starter motor as the solenoid comes wth it.
If you don't get the signal to the starter solenoid then it is some other electrical issue that probably needs to be diagnosed with the xentry or similar scanner.
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Joined: May 2024
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E class W212 E250
With 11.5 volts it should crank. I have been able to start my car with that low voltage.
If your car does not even try to crank then as the first troubleshooting step I would check if the start solenoid at the starter motor gets the 12V "signal" when you try to start. If signal is there but no crank then your starter motor solenoid is bad and you need to replace the starter motor as the solenoid comes wth it.
If you don't get the signal to the starter solenoid then it is some other electrical issue that probably needs to be diagnosed with the xentry or similar scanner.
If your car does not even try to crank then as the first troubleshooting step I would check if the start solenoid at the starter motor gets the 12V "signal" when you try to start. If signal is there but no crank then your starter motor solenoid is bad and you need to replace the starter motor as the solenoid comes wth it.
If you don't get the signal to the starter solenoid then it is some other electrical issue that probably needs to be diagnosed with the xentry or similar scanner.
Additionally, is there even a specific mechanism that stops the car from even cranking to prevent further drop in battery voltage, or it always tries to start?
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
P = U x I ... Power is the product of Voltage times Current
I dont think there is a low-voltage threshold that locks crank signal - See edits below... glow-plugs!
> You are doing yourself a disfavour by cranking on low-voltage:
-- The starter power is delivered with higher current that cooks everything in its path.
-- Marginal voltage soft-crashes computer modules and their CAN networking.
Having a Main battery low also drains AUX down to the same level. Charge AUX independently to prevent cooking its fuse.
+++++ E250... Diesel right???
ECU doesn't attempt to crank until glowplug controller is ready to get started.
This is not a low-voltage lock per se, it's a glow lock: No Glow = No Go.
> LOW BATT...
A new main battery will face the same challenges than the existing one. You may want to prevent battery voltage from getting low while parked or while driving.
If you decide to disconnect the main system batt, AUX if any will also need to be unplugged in trunk or dash. This is very effective besides using a CTEK float charger.
> You are doing yourself a disfavour by cranking on low-voltage:
-- The starter power is delivered with higher current that cooks everything in its path.
-- Marginal voltage soft-crashes computer modules and their CAN networking.
Having a Main battery low also drains AUX down to the same level. Charge AUX independently to prevent cooking its fuse.
+++++ E250... Diesel right???
ECU doesn't attempt to crank until glowplug controller is ready to get started.
This is not a low-voltage lock per se, it's a glow lock: No Glow = No Go.
> LOW BATT...
A new main battery will face the same challenges than the existing one. You may want to prevent battery voltage from getting low while parked or while driving.
If you decide to disconnect the main system batt, AUX if any will also need to be unplugged in trunk or dash. This is very effective besides using a CTEK float charger.
Last edited by CaliBenzDriver; May 14, 2024 at 07:01 PM.
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Joined: Apr 2016
Posts: 457
Likes: 151
From: Phoenix, AZ
2016 E350 Sport 2WD
Charge that main battery and also the Aux. When you're having electrical problems, it's always good to have a fully charged battery. Yes, many cars will start @11.5 or even @11, but having a full charge makes things work better.
Thread Starter
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Joined: May 2024
Posts: 7
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E class W212 E250
I dont think there is a low-voltage threshold that locks crank signal - See edits below... glow-plugs!
> You are doing yourself a disfavour by cranking on low-voltage:
-- The starter power is delivered with higher current that cooks everything in its path.
-- Marginal voltage soft-crashes computer modules and their CAN networking.
Having a Main battery low also drains AUX down to the same level. Charge AUX independently to prevent cooking its fuse.
+++++ E250... Diesel right???
ECU doesn't attempt to crank until glowplug controller is ready to get started.
This is not a low-voltage lock per se, it's a glow lock: No Glow = No Go.
> LOW BATT...
A new main battery will face the same challenges than the existing one. You may want to prevent battery voltage from getting low while parked or while driving.
If you decide to disconnect the main system batt, AUX if any will also need to be unplugged in trunk or dash. This is very effective besides using a CTEK float charger.
> You are doing yourself a disfavour by cranking on low-voltage:
-- The starter power is delivered with higher current that cooks everything in its path.
-- Marginal voltage soft-crashes computer modules and their CAN networking.
Having a Main battery low also drains AUX down to the same level. Charge AUX independently to prevent cooking its fuse.
+++++ E250... Diesel right???
ECU doesn't attempt to crank until glowplug controller is ready to get started.
This is not a low-voltage lock per se, it's a glow lock: No Glow = No Go.
> LOW BATT...
A new main battery will face the same challenges than the existing one. You may want to prevent battery voltage from getting low while parked or while driving.
If you decide to disconnect the main system batt, AUX if any will also need to be unplugged in trunk or dash. This is very effective besides using a CTEK float charger.
Of course, I haven't tried to start it too many times because I don't want to mess with any electrical systems, but at first when I turn the key the car tries to start, dash lights go a little dim and there is a click sound like something is trying to turn over (definitely not the engine itself), but then it stops. When I turn the key again, nothing happens, dash lights don't even go dim. Only way to repeat the car "trying" to do something is to removing the key and inserting it again.
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E class W212 E250
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MBWorld Fanatic!
Joined: Oct 2010
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From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
Hello, no, my car is gas, E250 cgi, M271 evo. I do drive it usually, but havent done so for a couple of weeks, and the battery itself is actually pretty old too.
Of course, I haven't tried to start it too many times because I don't want to mess with any electrical systems, but at first when I turn the key the car tries to start, dash lights go a little dim and there is a click sound like something is trying to turn over (definitely not the engine itself), but then it stops. When I turn the key again, nothing happens, dash lights don't even go dim. Only way to repeat the car "trying" to do something is to removing the key and inserting it again.
Of course, I haven't tried to start it too many times because I don't want to mess with any electrical systems, but at first when I turn the key the car tries to start, dash lights go a little dim and there is a click sound like something is trying to turn over (definitely not the engine itself), but then it stops. When I turn the key again, nothing happens, dash lights don't even go dim. Only way to repeat the car "trying" to do something is to removing the key and inserting it again.
Have you measured battery voltage while it tries to crank when you first turn the key? It may be below 10V and that would not start anything.
Get a new battery first and when it is running measure voltage so you know the alternator works.
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W212 FL
Why not replace the battery ? It's more than 10 years old and believe in me if it were a different car than Mercedes-Benz you should already have had to replace the battery by now . I know recharging also works but your car deserves a brand spanking refresh new battery
Out Of Control!!
Joined: Apr 2019
Posts: 11,921
Likes: 6,775
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
replace what now ???
it's not leaking.... can't be bad 
It's only just over 10Yrs.
By the time he changes the battery... we were all wrong... the starter toasted also.
It's only just over 10Yrs.
By the time he changes the battery... we were all wrong... the starter toasted also.
Last edited by CaliBenzDriver; May 15, 2024 at 01:23 AM.
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From: Cincinnati
2010 E350 4Matic
Just went through this not long ago. Car sat for a pretty long while, battery was 5 years old. Wouldn't crank. If I recall correctly voltage was around 11.5v. Would barely start with a jump. Wouldn't hold a charge. Had battery tested. It tested bad. Replaced battery. All good now.
Last edited by MBNUT1; May 17, 2024 at 04:40 PM.
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lexus
If your car does not even try to crank then as the first troubleshooting step I would check if the start solenoid at the starter motor gets the 12V "signal" when you try to start. If signal is there but no crank then your starter motor solenoid is bad and you need to replace the starter motor as the solenoid comes wth it.
Last edited by DeanMassy; May 21, 2024 at 01:49 PM.
