Alternator @ 14.1V but battery not charging
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W211 E63
Alternator @ 14.1V but battery not charging
Hi all,
I would really appreciate some advice please:
W211 E63
Recently replaced the battery with a Delkor AGM. When I charge it using a CTEK charger it charges to 12.9V;
With engine running the alternator shows 14.1V on the dash as well as at the battery terminals as measured with a multimeter; but
After a series of long drives the battery voltage drops to 12.2-12.6 after the engine has been off for a few minutes.
Is it possible that the alternator is providing sufficient voltage but not sufficient amperage to charge the battery properly? Could it be a voltage regulator fault which is causing this?
Thanks in advance for any advice.
I would really appreciate some advice please:
W211 E63
Recently replaced the battery with a Delkor AGM. When I charge it using a CTEK charger it charges to 12.9V;
With engine running the alternator shows 14.1V on the dash as well as at the battery terminals as measured with a multimeter; but
After a series of long drives the battery voltage drops to 12.2-12.6 after the engine has been off for a few minutes.
Is it possible that the alternator is providing sufficient voltage but not sufficient amperage to charge the battery properly? Could it be a voltage regulator fault which is causing this?
Thanks in advance for any advice.
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
paradox: discharged by driving...
you have the situation described well: ALT is charging but battery ends up discharged.
ALT voltage is variable based on needs of battery and heavy consumers (A/C, headlights, Defrost..).
You can get just about every voltage North of 12.6V and consider that normal... but if ALT output deeps below 12.5v then it is clearly taping your main AGM charge.
Have you see your car voltage come near 12.3v on the freeway ??
What range of charging current is you dash reporting ??
Can you get 14.x at idle rpm?
ALT voltage is variable based on needs of battery and heavy consumers (A/C, headlights, Defrost..).
You can get just about every voltage North of 12.6V and consider that normal... but if ALT output deeps below 12.5v then it is clearly taping your main AGM charge.
Have you see your car voltage come near 12.3v on the freeway ??
What range of charging current is you dash reporting ??
Can you get 14.x at idle rpm?
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W211 E63
Thanks. Yes it gets to 14.1V within 10 seconds of start-up and stays there +/- .2V the whole time. When I measured at the battery with a multimeter at idle it was also 14.1V so it doesn't appear to be a voltage issue, or a voltage drop issue between the alternator and the battery. THis made me wonder if a faulty voltage regulator could still output sufficient voltage without sufficient amperage?
Out Of Control!!
Joined: Apr 2019
Posts: 11,951
Likes: 6,796
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
new battery getting discharged by long drives...
Thanks. Yes it gets to 14.1V within 10 seconds of start-up and stays there +/- .2V the whole time. When I measured at the battery with a multimeter at idle it was also 14.1V so it doesn't appear to be a voltage issue, or a voltage drop issue between the alternator and the battery. THis made me wonder if a faulty voltage regulator could still output sufficient voltage without sufficient amperage?
Only voltage is regulated and the ALT will supply as much current as needed up to ~150A peak around 2000Rpm.
A 14.1v output at idle means the ALT brushes are not too short to feed the rotor winding.... good.
the way you say that long drive drain your battery makes me question what happen to car voltage after driving over an hour?
Does your car voltage swings down below 12.3 or stays above 12.6v ? Pay attention to voltage on longer drives.
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2005 e55 AMG
Hi all,
I would really appreciate some advice please:
W211 E63
Recently replaced the battery with a Delkor AGM. When I charge it using a CTEK charger it charges to 12.9V;
With engine running the alternator shows 14.1V on the dash as well as at the battery terminals as measured with a multimeter; but
After a series of long drives the battery voltage drops to 12.2-12.6 after the engine has been off for a few minutes.
Is it possible that the alternator is providing sufficient voltage but not sufficient amperage to charge the battery properly? Could it be a voltage regulator fault which is causing this?
Thanks in advance for any advice.
I would really appreciate some advice please:
W211 E63
Recently replaced the battery with a Delkor AGM. When I charge it using a CTEK charger it charges to 12.9V;
With engine running the alternator shows 14.1V on the dash as well as at the battery terminals as measured with a multimeter; but
After a series of long drives the battery voltage drops to 12.2-12.6 after the engine has been off for a few minutes.
Is it possible that the alternator is providing sufficient voltage but not sufficient amperage to charge the battery properly? Could it be a voltage regulator fault which is causing this?
Thanks in advance for any advice.
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W211 E63
Thanks for the comment. 12.6V wouldn't worry me but 12.2V on an AGM indicates ~40% discharge. I've read that the alternator will not generally get the battery at maximum voltage (only a charger will do that) but the drain on this one vs max capacity is far greater than on other vehicles I own.
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2005 e55 AMG
You are correct but remember these cars are not like others/ brands. They draw a lot when sitting. I just checked mine and it is sitting right at 12.3 volts.
Keep an eye on it each time you park it for a while but i think you will be safe.
Also every battery could be a tenth or so off when charged.
Keep an eye on it each time you park it for a while but i think you will be safe.
Also every battery could be a tenth or so off when charged.
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W211 E63
nothing regulates or limit the AMPS !
Only voltage is regulated and the ALT will supply as much current as needed up to ~150A peak around 2000Rpm.
A 14.1v output at idle means the ALT brushes are not too short to feed the rotor winding.... good.
the way you say that long drive drain your battery makes me question what happen to car voltage after driving over an hour?
Does your car voltage swings down below 12.3 or stays above 12.6v ? Pay attention to voltage on longer drives.
Only voltage is regulated and the ALT will supply as much current as needed up to ~150A peak around 2000Rpm.
A 14.1v output at idle means the ALT brushes are not too short to feed the rotor winding.... good.
the way you say that long drive drain your battery makes me question what happen to car voltage after driving over an hour?
Does your car voltage swings down below 12.3 or stays above 12.6v ? Pay attention to voltage on longer drives.
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04 E55 AMG (totaled), 07 S550 4Matic, 14 E63S
If you are not getting load shedding when you are driving or when you cold start the engine, then I don't know that I'd be chasing any issue at all. All of my issues of this kind were resolved when I replaced the old OEM battery.
Senior Member
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From: East Coast, USA
Mercedes CLS 55 AMG
I will keep looking on longer drives but certainly have not seen it drop below 13.9 before. Reading SICAMG's comments it doesn't seem to just be me...I've never had a vehicle before where the normal state of battery charge is so much lower than maximum. Oh well I guess I will just keep using my CTEK regularly.
If your battery is showing 12.1-12.2 volts, it's very discharged. Period.
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2005 e55 AMG
You are correct. But I am looking at voltage when the car sits say over night or so and meter to meter will be a little off. So your 12.5 is pretty close to my 12.6 number but again meter to meter is never exact.
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From: East Coast, USA
Mercedes CLS 55 AMG
You are correct but remember these cars are not like others/ brands. They draw a lot when sitting. I just checked mine and it is sitting right at 12.3 volts.
Keep an eye on it each time you park it for a while but i think you will be safe.
Also every battery could be a tenth or so off when charged.
Keep an eye on it each time you park it for a while but i think you will be safe.
Also every battery could be a tenth or so off when charged.
There's a big difference between 12.1, 12.3, and 12.5 in terms of voltage. My meter is exact. We're not talking 12.51 vs 12.50. Less than 12.50, in my opinion, is very discharged. I'm not even happy about 12.50, but there's a certain amount of drain before the car actually "sleeps" and my Bosch battery is about 3.5 years old at this point.
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04 E55 AMG (totaled), 07 S550 4Matic, 14 E63S
That's the thing. You can't really check state of charge unless the battery has no load. If there is a load, it will pull down the voltage lower than the true resting SoC reading. Obviously a load big enough to pull down the battery to 12.2 resting voltage means there is a draw. But you really should let the car sit overnight and check in the morning. Leave the trunk open so you don't wake it up to access the battery. That will be the closest to resting voltage UNLESS there is a significant draw.
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2005 e55 AMG
I better stick to the simple stuff like transmissions and engines. My electrical skills have always been a struggle LOL
Every time I diagnose an electrical problem I consider it a Christmas miracle ! LOL
Every time I diagnose an electrical problem I consider it a Christmas miracle ! LOL
Senior Member
Joined: Aug 2015
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From: East Coast, USA
Mercedes CLS 55 AMG
That's the thing. You can't really check state of charge unless the battery has no load. If there is a load, it will pull down the voltage lower than the true resting SoC reading. Obviously a load big enough to pull down the battery to 12.2 resting voltage means there is a draw. But you really should let the car sit overnight and check in the morning. Leave the trunk open so you don't wake it up to access the battery. That will be the closest to resting voltage UNLESS there is a significant draw.
I understand what SICAMG is saying about the voltage showing 12.1-12.5~ , but if you're checking a battery the way I described above it should be damn close to 12.6. Otherwise I'd say the battery is bad, the battery is made by Interstate and it's garbage, or you have a draw.
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W211 E280
What was causing this, I have the same issue
you have the situation described well: ALT is charging but battery ends up discharged.
ALT voltage is variable based on needs of battery and heavy consumers (A/C, headlights, Defrost..).
You can get just about every voltage North of 12.6V and consider that normal... but if ALT output deeps below 12.5v then it is clearly taping your main AGM charge.
Have you see your car voltage come near 12.3v on the freeway ??
What range of charging current is you dash reporting ??
Can you get 14.x at idle rpm?
ALT voltage is variable based on needs of battery and heavy consumers (A/C, headlights, Defrost..).
You can get just about every voltage North of 12.6V and consider that normal... but if ALT output deeps below 12.5v then it is clearly taping your main AGM charge.
Have you see your car voltage come near 12.3v on the freeway ??
What range of charging current is you dash reporting ??
Can you get 14.x at idle rpm?
I am facing the same issue.
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W211 E63
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W211 E280
I found the problem, its the Gateway module issue
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W211 E63
9450 B31 C-AAC multifunction sensor
9354 No CAN message received from rear SAM
90E2 CAN comm with REAR SAM is sporadically disturbed
9098 Control Unit N10/2 (Rear SAM control unit with fuse and relay module) is not transmitting data on the CAN bus
930C Knowledge base configuration incomplete
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W211 E280
Did you check your gateway?
I got a Foxwell NT530 Benz scanner and it detected the following codes...one or of them may explain it but in the meantime the Ctek is the most cost-effective answer given I've had to prioritise an airmatic valve block replacement too...I also disconnected the power seat connectors given the known issue with them but it didn;t have any effect.
9450 B31 C-AAC multifunction sensor
9354 No CAN message received from rear SAM
90E2 CAN comm with REAR SAM is sporadically disturbed
9098 Control Unit N10/2 (Rear SAM control unit with fuse and relay module) is not transmitting data on the CAN bus
930C Knowledge base configuration incomplete
9450 B31 C-AAC multifunction sensor
9354 No CAN message received from rear SAM
90E2 CAN comm with REAR SAM is sporadically disturbed
9098 Control Unit N10/2 (Rear SAM control unit with fuse and relay module) is not transmitting data on the CAN bus
930C Knowledge base configuration incomplete
