Battery charge indicator?
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Joined: Dec 2014
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Battery charge indicator?
2021 GLC 300 : analog-style drivers guages has "charge" as a continuation of instantaneous mpg indicator. What is it showing me?
MBWorld God!
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It just means the alternator is doing its thing, since your vehicle isn't an electric vehicle or hybrid vehicle, it wouldn't have regenerative braking so in your case it is the alternator charging the battery.
Thread Starter
Member
Joined: Dec 2014
Posts: 179
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Euro part on USA GLC300?
Been watching the behavior of this little guage: it only shows green for a few seconds and only when consumption guage shows "999" mpg. Since I don't have regen and since my alternator is always outputting 14+ V, the system must be checking the status of SOMETHING, perhaps that secret little starting battery I use so often with the default eco stop/start function?
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Been watching the behavior of this little guage: it only shows green for a few seconds and only when consumption guage shows "999" mpg. Since I don't have regen and since my alternator is always outputting 14+ V, the system must be checking the status of SOMETHING, perhaps that secret little starting battery I use so often with the default eco stop/start function?
Thread Starter
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Joined: Dec 2014
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
I didn't explain that well: 999 mpg only occurs while decelerating with foot off the throttle; like going downhill in gear.
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I see, thanks for the follow up. If you haven't notice, putting the vehicle in glide mode/coast mode the green charge will show up as well. The green charge also shows up when the vehicle has completely stopped right?
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Joined: Dec 2014
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Putting vehicle in glide/coast mode does not bring up green bar. Only deceleration with zero throttle brings it out and then only briefly.
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MBWorld God!
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Have you scanned the vehicle for any codes just in case there might be (as in a possibility of) a slight malfunction?
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2016 GLC 250d AMG pack, 2017 GLC Coupe 250d AMG pack , 2002 BMW 330Ci convertible, 2021 BMX X1 sD20i
I think all this is related to the ‘secret battery’ !!
the charge indicator that disappears refers to charging up the AUX Battery that in reality is a small black box hidden under footwell carpet in passenger side that houses a capacitor.
In reality it is a voltage regulator.
These last around 4 to 6 years before needing replacement - the capacitor gives up and needs replacing.
If the car battery degrades or needs charging the stop/start function stops the alternator will never fully charge up the main battery due to AGM construction and higher volts needed.
Regular evening charging of main battery with a smart battery charger, kike CTEK, will lengthen battery, Volt regulator and minimise weird electronic issues that go away when main battery fully charged.
the charge indicator that disappears refers to charging up the AUX Battery that in reality is a small black box hidden under footwell carpet in passenger side that houses a capacitor.
In reality it is a voltage regulator.
These last around 4 to 6 years before needing replacement - the capacitor gives up and needs replacing.
If the car battery degrades or needs charging the stop/start function stops the alternator will never fully charge up the main battery due to AGM construction and higher volts needed.
Regular evening charging of main battery with a smart battery charger, kike CTEK, will lengthen battery, Volt regulator and minimise weird electronic issues that go away when main battery fully charged.
MBWorld God!
Joined: Dec 2019
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I think all this is related to the ‘secret battery’ !!
the charge indicator that disappears refers to charging up the AUX Battery that in reality is a small black box hidden under footwell carpet in passenger side that houses a capacitor.
In reality it is a voltage regulator.
These last around 4 to 6 years before needing replacement - the capacitor gives up and needs replacing.
If the car battery degrades or needs charging the stop/start function stops the alternator will never fully charge up the main battery due to AGM construction and higher volts needed.
Regular evening charging of main battery with a smart battery charger, kike CTEK, will lengthen battery, Volt regulator and minimise weird electronic issues that go away when main battery fully charged.
the charge indicator that disappears refers to charging up the AUX Battery that in reality is a small black box hidden under footwell carpet in passenger side that houses a capacitor.
In reality it is a voltage regulator.
These last around 4 to 6 years before needing replacement - the capacitor gives up and needs replacing.
If the car battery degrades or needs charging the stop/start function stops the alternator will never fully charge up the main battery due to AGM construction and higher volts needed.
Regular evening charging of main battery with a smart battery charger, kike CTEK, will lengthen battery, Volt regulator and minimise weird electronic issues that go away when main battery fully charged.
Thread Starter
Member
Joined: Dec 2014
Posts: 179
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Hmmm, I recall that it displays charge and the green bar shows up on my 2017 (sedan) during coasting with the sailing boat icon but I have a C 43 but should be the same, I need to check to see if I remembered it correctly next time I take a drive.
Have you scanned the vehicle for any codes just in case there might be (as in a possibility of) a slight malfunction?
Have you scanned the vehicle for any codes just in case there might be (as in a possibility of) a slight malfunction?
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Yup, exactly. I wouldn't worry about it unless you clearly see something wrong like unable to start a vehicle, CEL, etc. I believe everything is working as intended. I will let you know if I see the same behaviour on my 2017, been getting blizzards lately in my area so the vehicle is taking a break in the garage. That being said, I had a pre-facelift C-Class so it might have changed so it is not exactly oranges to oranges comparison.
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OP, here is an excellent post by superswiss explaining how it all works: https://mbworld.org/forums/s-class-w...ml#post8505582
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Joined: Dec 2014
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Yes, but
Great article, thanks for the url. Takes me further on my quest but now I have more questions. "the alternator never actually fully charges them to leave some room for recuperation" Huh? Why not? Why is the period of increased charge relegated to only throttle-off deceleration? And, isn't this behavior EXACTLY how regeneration works?
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2019 C63CS
Great article, thanks for the url. Takes me further on my quest but now I have more questions. "the alternator never actually fully charges them to leave some room for recuperation" Huh? Why not? Why is the period of increased charge relegated to only throttle-off deceleration? And, isn't this behavior EXACTLY how regeneration works?
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From: San Francisco Bay Area
2019 C63CS
Hmmm, I recall that it displays charge and the green bar shows up on my 2017 (sedan) during coasting with the sailing boat icon but I have a C 43 but should be the same, I need to check to see if I remembered it correctly next time I take a drive.
Have you scanned the vehicle for any codes just in case there might be (as in a possibility of) a slight malfunction?
Have you scanned the vehicle for any codes just in case there might be (as in a possibility of) a slight malfunction?
Thread Starter
Member
Joined: Dec 2014
Posts: 179
Likes: 29
From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Assimilating........
And I wonder how I can access "the workshop menu" with those nifty stats. I can't see my state of charge on mercedes me app.
And I wonder how I can access "the workshop menu" with those nifty stats. I can't see my state of charge on mercedes me app.
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2019 C63CS
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Yes, it's a mild form of recuperation. Ever since car manufacturers replaced belt driven components in modern cars with electric equivalents such as electric power steering, electric on-demand oil pumps etc. there's increased demand for electric power and also to really reduce fuel consumption, the alternator periodically gets decoupled from the engine and the electrics are powered from the battery. The decoupling reduces drag on the engine, hence saving fuel. So just like in electric cars, it makes sense to recuperate some of the kinetic energy when coasting and put it back into the 12V battery so it can later be used to power these electric components with the alternator decoupled. So when you see that charge indicator, it's just like in an EV. It recuperates some of the energy by increasing the charge to the 12V battery. You won't see the charge indicator when glide mode is active, as then the engine is decoupled from the transmission and idles, so there's no recuperation.
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W212 MY'14 M276-3.5NA @75kMi
THE BLEEDING EDGE
I just realized part of this is a result of battery draining when idling: https://mbworld.org/forums/mercedes-...s-voltage.html @CaliBenzDriver
In 2014 ECU voltage remote controlled by Rear-SAM driving ALT output was so
Hopefully the core timings of the GLC300 engine no longer rely on stable voltage else engine is bound to be moody instead of a smooth torquy Benz engines.
@W205C43PFL can help you troubleshoot the various conditions your chassis may be struggling with.
Last edited by CaliBenzDriver; Jul 22, 2025 at 02:44 AM.
MBWorld God!
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This power management may now have a chance to be useful on 2021 engines. Put the system through its paces for gentle testing of its fundamentals.
In 2014 ECU voltage remote controlled by Rear-SAM driving ALT output was sobuggy ahead of its time it helped the engine run poorly. A great idea poorly freshly integrated.
Hopefully the core timings of the GLC300 engine no longer rely on stable voltage else engine is bound to be moody instead of a smooth torquy Benz engines.
@W205C43PFL can help you troubleshoot the various conditions your chassis may be struggling with.
In 2014 ECU voltage remote controlled by Rear-SAM driving ALT output was so
Hopefully the core timings of the GLC300 engine no longer rely on stable voltage else engine is bound to be moody instead of a smooth torquy Benz engines.
@W205C43PFL can help you troubleshoot the various conditions your chassis may be struggling with.
Out Of Control!!
Joined: Apr 2019
Posts: 12,191
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
MBWorld God!
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I think the main question was answered, being what is the charge bar, the reason I brought you here so you can see this thread and forum member superswiss' reply on the fuel savings and emissions, regulations that implemented resulting in the alternator not charging in certain conditions, running the starter battery to power electronics while the engine is running and more on how this variable "smart" alternator works etc. but I think you know all of this already : ) but just in case...
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
UNSTABLE VOLTAGE CONTROL
I think the main question was answered, being what is the charge bar, the reason I brought you here so you can see this thread and forum member superswiss' reply on the fuel savings and emissions, regulations that implemented resulting in the alternator not charging in certain conditions, running the starter battery to power electronics while the engine is running and more on how this variable "smart" alternator works etc. but I think you know all of this already : ) but just in case...
When everything is running well, it sounds like more power reclaimed.
Perhaps the X253 chassis handles the low voltage normally without disturbance:
- -- Engine throttle should be nimble & strong
- -- Tranny shifts should be seemless & instantaneous
Experiment stable voltage for 500.Mi. to see what's missing.
What's involved is the variable voltage in solenoid and coils directly affect results:
- the ignition sparkplug coils
- the Throttle-body electric step motor
- the tranny valve-body shift solenoids
This may translates in approximative throttle response and bangy shifts.
Last edited by CaliBenzDriver; Jul 23, 2025 at 04:08 AM.
