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Since your able to drive around, swing by an auto parts store (or dealer) and ask them to put a battery analyzer on it. If there's a dead/shorted cell, or some other defect in the battery, the analyzer will detect it. If the battery checks out OK, then you can start worrying about the alternator and/or regulator.
Testing the battery was the first thing I did. With my Solar tester , and by charging it from 725 Cca to 850 with a CTEK (850 is the rating ) and I got it tested at an auto parts store. And the alternator charges, it just takes a vacation every month. Read the whole post. CaliMB has something to say that nobody knows about .
CaliMB , I read one of your old posts where you said On acceleration, charging stops for more performance, yea that drove me to almost a heart attack yesterday not knowing this is normal! What other quirks are there ?
We had a New BMW 750 Xli x drive Individual, 7 years ago. That car had massive charging issues BMW could not fix , I was charging it every night for awhile, in the first 6 months!
1-- MAIN:
You say disconnect the Control Connector,
what does it look like?
What does it do?
What happens when I disconnect it?
What are the drawbacks?
2-- AUX:
Are there any negatives to having a bad Auxiliary battery, as mine has been giving me notices for years !
I enjoy stop start not functioning! but it will function and bother me most days after awhile. The battery is not dead just weak.
You've evidenced how your car is draining your main battery while driving. Now you're concidering solutions.
As mentioned in this thread, I know of 2 workarounds I have personally comed up with to keep the alternator powering the car well without disfunctional "yoyo" voltage below 12.3V.
Simple Headlights:ON
ALT default mode
1-- MAIN AGM:
Regarding the disconnection of the ALT Control Connector:
> What does it look like?
ALT has two wired connections. A fat cable bolted on and a tiny wired using a connector... disconnect that connector!
> What does it do?
It lets the voltage regulator work is self-controlled default mode. The alternator control is normaly done through a digital messaging over a LIN serial link.
The smart regulator is independently intelligent to measure both load current and output voltage to deliver a well regulated voltage, without any instructions from ECU.
> What happens when I disconnect it?
The alternator supplies perfectly regulated power to all car electricals loads non-stop. This keeps the starter battery fully charged. This can be witnessed by a decreasing charge current tending towards zero under fixed voltage.
> What are the drawbacks?
To my knowledge there just aren't any significant ones.... You won't get the useless 14.9V bursts, nor the 12.6V float and won't need to replace prematurely failed battery. So its bad for business
2-- AUX:
I don't know the drawbacks of not having a healthy AUX batt besides disabling Engine-Cut-Off.
AUX exist to supply backup power to essential systems when Main batt ghost or during ECO Restart.
Overall I can't recommend not servicing it to stay on the safe side of AUX circuitry.
Batteries are connected and disconnected from their respective circuits by SAM's using 2 nearby relays either solid-state SSR or conventional SPST.
Enjoy your well powered Mercedes.
Last edited by CaliBenzDriver; 09-24-2022 at 04:20 PM.
Yes the last time this happened you can see it lasted about 4 days. That was 4 days when everything was like all other days . So there was no reason for this to happen. Actually voltage was not low when this happened but the battery took up about 100a using my charger, so something wasn’t right.
Yes the last time this happened you can see it lasted about 4 days.
That was 4 days when everything was like all other days . So there was no reason for this to happen.
Actually voltage was not low when this happened but the battery took up about 100A using my charger, so something wasn’t right.
> Deep drained over 4 days.
That's interesting.
Did that discharge happened during driving or during parking? Causes are different accordingly (ECU vs. SAM)
> Charging near 100A with charger.
I have seen stupid alternator shuve 90Amp into a drained battery but don't know any "charger" that will do that to a low battery.
> Voltage was not low but battery was drained to 20%.
Lead-acid battery voltage deeps linearly with the charge level.... what was voltage measured under load or resting condition??
> Log Graph:
I see battery charge reported being low over a period with 9 short partial charging steps.
In order to make sense of things you have to link the conditions with the measurements to understand the meaning of what you're seeing.
Hope this helps you get a handle on charging issues.
Cali, I read one of your old posts where you said On acceleration, charging stops for more performance, yea that drove me to almost a heart attack yesterday not knowing this is normal! What other quirks are there ?
We had a New BMW 750 Xli x drive Individual, 7 years ago. That car had massive charging issues BMW could not fix , I was charging it every night for awhile, in the first 6 months!
All the fancy features in our Benz are actually just 3rd party designs picked to be showcased by leading car makers.
We buy cars from reputable brands hoping to get great experience. It's not entirely the case... some chaos comes interlaced in German products.
When cars are defective from factory, they should all get fixed through campaigns... not lip-service.
This design is named "opportunistic charging" - The firmware runs in the ECU that collects data from the main battery (Temp, Volt, Amps) to request a taylored voltage output from the alternator.
The whole dynamic voltage scheme works gloriously until the feedback from AGM sensor through SAM goes disfuntioning.
Stupid ECU dont know what to do and stops controlling ALT that goes offline.
At that point ALL 100% of POWER come out of AGM until ECU regains a grip.
You then get an unlimited amperage punch of charge into AGM instrad of normal smooth voltage transitions.
When charging system works well car is drastically well behaved. Even the noisy piezo injectors are much quieter, different injection mode.
Like I said earlier the wasted batteries are only the tip of this iceberg! This issue involves disrupted CAN.
✌️
The discharge over 4 days was driving the same as every day, car was used every day. No Stop Start used, one hour a day, daytime city driving as usual.
I stated the charger and 100amps, I meant to say the battery accepted 100+ amps, the battery tested at about 730 and charged to 835-850cca tested by a Solar battery tester. It is a 850 Cca battery .
My Sears Die Hard charger (showed 83%charge) was set to 10 amps and ran about 1.5 hours .
Then I used the CTEK for 6 -8 hours at I believe 4 amps . Voltage didn’t really drop over the 4 days but capacity did.
I wonder if stuck brushes could cause this. I just received a new regulator I will try .
The Glk has been sitting since Friday morning 44 hours , % charge has only dropped from 81-80%, and voltage from 12.61 to 12.57.
Checked with the CTEK remote battery sensor and app. I think that is normal. I wonder about sticking worn brushes.
This is what the CTEK recorded as voltage on the 4 days , it looks normal, I don’t think the CTEK is accurate on either voltage or % of charge . I think the volts are more 9/13-9/18 , all these amp and v readings can’t be accurate, I do know the battery absorbed 110 amps to bring battery to 100%
accurate. So do I have a problem or am I wasting time, the battery did accept about 110a over about 6-7 hours
I see now what you mean by "100a"... it's charging from 750CCA to 850CCA under 5 or 10Amp charging current.
Thing that's confusing for me is "750CCA" charge level is nowhere near 20% charge level measured by CTEK Log...
I hope your new regulator delivers expected results. It's a good maintenance step around 110kMi when soft brushes get short. Only use the OEM replacement because unbranded China copies groove the soft coper rotor rings: wasted alternator!
Personally I rely on Volts & Amps measured by battery sensor that's shown by iCluster.
The missing 10Amp charge you've seen on Cluster correlates to what your Sears charger delivers.
That is not a bad charging current. ✔️
To witness battery drain to 11V with alternator: OFF and swing current in the 50 to 90A territory, you may drive on highway at steady speeds for over an hour - See what happens to your Amps and Volts.
Last edited by CaliBenzDriver; 09-25-2022 at 12:06 PM.
Shouldn’t the alternator keep it near 100% charged ?
Not the 80% I now get ?
thanks for your help,
The matching FCP regulator is a genuine OEM part. It should easily extend the life of these alternators for another 100kMi.
80% is the target threshold to stop opportunistic 14.9V bursts during decelerations.
100% full charge target is reached with standard 14.4V at decreasing current. "Null current" causes the ECU to then gradually ramp down (not with steps.... smooth ramp!) power supply voltage.
13.7V is used to supply high-loads "consumers" after the battery gets full, nearly null current afterwards.
12.6V float voltage is used after full charge in absence of significant loads (No A/C, No HL) - - This is when hell brakes loose.
Overall the car voltage keep changing smoothly.
What never changes is the battery keeps accepting current, never supplying any load during drive cycle besides start and ECO. Deep draining battery is not in the book!
> PRACTICALLY ... :
When you drive arround town, you should see a rapidly decreasingcharge current from 12A to 1Amp as the battery is getting closer to full.
To diagnose charge condition it's easier to focus on the current than variable voltage:
> BAD: Increasing current numbers (+/-) means lack of charging progress.
35Amp is deep discharge territory!
> GOOD: Decreasing current means charge is accumulating well.
15A decreasing to 0.5A is normal.
Last edited by CaliBenzDriver; 09-25-2022 at 10:35 PM.
Right above, we've seen how the ECU taylors the car voltage to fully charge main battery ASAP.
Having 100% alternator control, the ECU firmware understands how the car is driven. It is able to deliver a smart voltage control referred to as "opportunistic".
This great Bosch design is shared in various forms with most car makers.
> DECELERATIONS :
When slowing down the car, the ECU helps by maxing out charge voltage to increase the alternator load on the engine.
These bursts of 14.9V only happens below 80% charge. There after from 80 to 100% this scheme is disabled and decelerations cause no voltage change.
> ACCELERATIONS :
When speeding up, the ECU lessens the engine load by backing down voltage to pause charging: Nothing gained, nothing lost.
Whatever charging stage the battery is in the alternator output gets matched to a lower voltage such that battery current gets null.
Again here... that's when hell can brake loose in affected cars!
Instead of normally going to a 13.7V or 12.6V a crazy alternator output goes off! Purely out of the circuit, 100% load comes out the battery through PreFuse module for a lengthy period.
> DOUBLE DOWN : Not only the battery can get drained, it may also get left supplying 100% of entire load.
-- GOOD: When the voltage is lowered on a well working car, it is transparent because the ALT still does/should power 100% of the car electric load. Battery current stays very low, nothing lost. From about 30A base load to around 120Amp with engine fan spinning still come from ALT.
-- BAD: When normal control crashes, the ALT gets turned OFF!!! Batt picks up 100% of load.
->1- On a young battery this load transition can drop the Fuel Pump pressure regulation. Instead of a rich mixture acceleration boost you get slumpy performance.
-> 2- On a battery both drained and worned out by abuse cycles, voltage drops in the weeds: driver earns a LIMP MODE wake up call.
Car engine-tranny cuts-off, speed goes to 5mph. On the highway it can be deadly.
No direct DTC code to repair: "could not reproduce", come again!
> SELF-FEEDING CHAOS:
Marginal voltages crash CAN communications, that overwhelms couple modules (SAMs, ECU) firmware with junk data.
That leads to crashing the ALT control and delivers even lower voltage.
> HALF-BAKED : That excellent engineered chaos is a little over done as it crosses safety limits when it becomes dangerous.
Bosch owns the creation of the CAN protocols and this distributed feature built on top of it. They have an extremely keen understanding of how to deliver reliable designs such as ABS/ESP brakes controls.
Fault-tolerance, quality control, self-certification all got bypassed like with Boeing 737-Max with amazing results in the leadership race.
👏
At the end of the day, I think using my advanced workaround solutions is a pretty satisfying. I am still testing further fixes and gathering hands-on understanding.
* In memoriam for my brother who passed away yesterday SEP 25 on myocardial fibrillations... "blue pills" not your friend.
Last edited by CaliBenzDriver; 09-26-2022 at 03:30 PM.
I put in the new MB regulator today from Fcp , voltage is much more even and it was just done an hour ago so no full results yet. At idle it stayed higher.
72000 miles and the brushes were worn out, rear brush about 1/8”, front brush a bit more and commutator was black. I cleaned the commutator and connections . After only 20 minutes drive it load tested 810 Cca , and that’s as good as the CTEK could get it overnight.
I think I’m ok! Thanks for your help.
That is good news right before the weekend. I hope it stays fixed with all that much power like new.
Battery should get charged reliably well and transition through stages without being discharged.
my Valeo reg swap was no help
These smart regulators are packed with firmware. Getting that to match the ever changing Bosch landscape can't be easy. After all I thought a $50 replacement would make sense. No difference, so I kept my original MB part.
You started this thread after ordering your regulator
🤞
Last edited by CaliBenzDriver; 09-30-2022 at 08:34 PM.
6 days later , it looks like it was the regulator. It is as fully charged as the CTEK would get it. A 2 year old 850cca battery charging to 822 Cca is 100% in my opinion. I also replaced the auxiliary battery since every day I had dash warnings it was bad. I thought as sophisticated and interconnected this system is, I didn’t want to risk it. At 72000 miles one brush was at 1/8”, well below the 1/4” minimum. I also cleaned my commutator which was black . Thank you for the help.
Hi Mmr1, can you give us some feedback. Does the regulator/brushes fixed the problem? My charging system is acting like crazy these days. How hard was it to change the regulator. Thanks
09-24-2022, 12:21 PM
