Hi I got the red BATT ALARM on dash after driving 20km, turn around and back.

1-On steering I could go check "OK" and it went away.
2-Going to Services I saw the Alarm, checking it here it stuck on RED dash.

3- Back at home it charged 14.1/14.05/13.9 varying,it looks it is charging.

I had the battery on charge with CTEK charger over 3 days, off at night.
Not because it wont start, But because not wanting to start it if low-precaution.
Not sure if this could cause something.

4-The battery is a Varta F19 12V 85Ah 800A....Silver Dynamic.
Year 2016-09-30.
Its now 2025-09-30
Km,s=157 907km

Just asking if agree battery is old enough, if its the battery(It still starts easily).
-they want to sell me a Lead Acid replacement battery, program computer to notify it about batt change if necessary.(4-Year last)
-The AGM type it looks I can only get from Dealer at 3-4 times the price hopefully (last 8 years again)-?

 

Who is “they”?

Go to another store, MB doesn’t have a monopoly on AGM batteries. Walmart has them and certainly at autoparts stores.

9 years is plenty old for failure.

 

My previous MB battery was 7yrs old when it finally stopped holding a charge and I replaced it.

I bought a replacement battery at my local MB dealer, was around $210 after returning the old battery for core charge refund. Since then I realize they sell AGM batteries at Walmart for a little less money and longer warranty. MB battery was only 2yr warranty from date of purchase.

I replaced the battery myself. It was easy, just need a socket set or wrench. No programming needed.

 

The voltage after few hours after running is now=12.45Volts, its not completely dead as I experienced with Lead Acid batteries.
Maybe I killed it faster with a CTEK charger over 3 days during daytime-?
- I am trying to get AGM options.....

 

12.45v seems fine to me. I was having a red battery warning pop up on my dash awhile ago and did alot of testing. The warning stopped coming on so I never did anything with it.

I was using two inexpensive battery testers and a multimeter.

 

Old battery may well be shot (slow crank) but no one talked about checking the ALT power supply.

Starter battery is just a storage, it does not generate any power!

-- Note CTEK does not "kill batteries", the opposite: it lowers internal resistance.


Check old ALT does generate power above 13V to carry 100% of chassis load (A/C load + HL+ rear defrost...)
If running voltage is found low, you may need a new brush-set...

 

DEL

 

Its interesting, the BATT Alarm in my case also went off after I switched it off and restarted. It came on after I slacked down(20Km), and made a U-Turn.

I will see tomorrow if it comes on again(Check Voltage again). The previous battery at 8 years went to 11.4=Click Click on start, no start. That's when it was replaced with this one, just realized another 17 years of my life gone as well.

Note: It was charging fully(Green) on CTek, I just removed it and drove off.

 

Can you learn to display voltage on your IC display while driving.

You will be able to witness how voltage & amps flow in/out of batt/ALT

 

The red battery warning can mean anything from the battery to the charging system. Not just the battery.

I would scan the car for any faults.

Mercedes specific obd scanner comes in very handy.

 

OK, here is the Voltages measured with Voltmeter through windscreen(The Voltage menu display does not work in this car)

1-Last night=12.45V
2-This morning=12.44V

3-Switched on stage-1=It drops to 12V.
4-Switch on stage-2=It drops further to below 12V.
5-1st start attempt=It started ok.......Running...no charging for say 2-3 seconds
-----The voltage go up to 13+V, then down, then up, then the BATT ALARM came on and the charging is rejected(It looks).
-Switched off. Check no messages, alarm gone
6-2nd start attempt=It started ok below 12V, but no attempt this time to charge batt-?

So is the Alternator faulty or the batt draw too much amps and the charging is rejected-?
-Serpinetine belt ok and relative new.

What do you think on this-Battery done, Charge rejected, or alternator faulty or both-?
Note: I did not revved up the engine at all.
Note:The battery lenght(AGM) measured at 231mm, does that sound right-?

 

There, your evidence gathering is consistent with low ALT voltage.

Chassis voltage should be supplied near 14V, not 12V.

Your new belt may be responsible for not spinning ALT properly
or ALT may no longer be putting out power.

At least main battery is now out of question.

 

I realise the double wammy coming....., 9 year battery plus alternator cost.

Note:I may have caused this problem myself. Changing the oil recently, the oil spilled, and run over alternator, not the belt or pully, I did not see it in time. I wiped it off, but maybe it get through, not sure if brushes sits at front of alternator.
Ok< thats that then....

-------------------------------------------Experiment -2:
I just want to carry out another experiment to satisfy myself without get somebody reading codes at more cost......

1-I am charging the battery up again with CTEK.
2-Purpose is to see if alternator charge at all with battery fully charged, so the battery does not draw so much amps...I could hear the engine load up when it charge 13V+, then load down again , load up again, then down and it's over charging attempt any further.
3-So if it charges steady when battery don't need serious help, maybe that means something(Alternator Protection build in-??)-?

------------------
Previous experience many years ago(Short version). Just out of school. No solar power

I volunteered to build my uncle on a remote farm when 12V-TV's came out a 12V Generator. Decided to use a VW Beetle alternator.
I learned that pulling that alternator on two flat batteries at 10V, you need an engine at least 5HP at 3000RPM like in VW Beetle running.
I learned that the Alternator gets extremely hot, you cannot touch it, I had to make a fan & cooling enclosure which works.
I added a trip circuit to trip out at 14.9 Volts, then the batteries are usable again.
I used my two batteries of fathers vehicle and mine to test and setup/adjust trip circuit.
----I then went out and bought two new lead acid batteries of same as as tested ones, and then this surprise. Both the voltage drop so fast after 14.9V, the engine restarted again in a circle.
----Result=Both new batteries failed a load test new(Was charged), they gave me two other batteries and they both passed(Cut out adjustment).
---I then bough a cutout circuit with delay setting to make sure engine stops to avoid same trap if batteries getting older.
------So since then, I always wonders how good is that new battery you just bought without load testing it-?
------Maybe those are the ones only lasting like 2 years instead of 4....-END

 

OK, I charged up the battery with CTEK Nto 13.9Volt.

1-Switch on Stage-1=Voltage drop immediately to 12.30Volt.
2-Switch on Stage -2=Voltage drop to 12Volt.
3-Engine starts and run=Voltage drop below 12V, 11.84 stay there........This time the alternator charges nothing at all, even if I rev the engine-Nothing.

Will there be indications if a fuse blown somewhere-?

 

Ok, quick decissions. I went to the Auto shop in local town that sold me this Varta battery that lasted 9 years, he is totally clued up on Mercedes John Deere etc, Bosch dealer.
_The reasom I did not go this time at 1st, is his clerk told me they don't do batteries anymore about a year ago, so I took a change today and he changed his mind, dealt with him before very reliable reasonable.

He will look at it tomorrow, he got a new battery AGM for me, and said the oil on alternator will cause problems, so maybe I am lucky and not a complete new alternator, and if slip rings not damaged, just cleanup & brushes.
-He knows the control module and said my car has one.

-No lead acid battery in this car his words.

So, I let you know how it turned out hopefully in a weeks time.

 

What is your VIN #?

If your alternator is not properly working you may be able to just replace the voltage regulator which is a less expensive option than replacing the alternator.

When I was testing out my charging system I bought an inexpensive battery tester that I hooked directly to the battery and with bluetooth allows me to view the voltage as im driving. I found it handy. What it showed me was as soon as i started the car the voltage went up indicating the alternator was fine. Heres a link to the thread I made on it. Theres alot of useless information but gives you an idea of what I did: https://mbworld.org/forums/c-class-w...eadings-2.html

 

How are you reading the voltage? via a Scan tool?

My tool will let me know some actual live data, and battery and charging is one of them. 9 year for a acid battery is too long, I think either is low on electrolyte, or one of the plates is already damage. Considering the age, is not hard for that to happen.

Replace the battery is pretty direct, no need of programming.

If still unsure of buying, i will check how long the battery is holding charge while disconnected from the vehicle, after 1, 2 6 and 8 hrs. Voltage should not go down fast, in a short period of time

 

-With Voltmeter at front window.
-The battery is a AGM Varata
-Its going to a local shop to get fixed, he has a new AGM battery, and Alternator may not be a complete replacement, will see tomorrow.

 

You can see the voltage using the ASSYST PLUS menus from the dash display.

Follow the first set of instructions for Calling up the workshop menu. Then when your screen looks like in the photo below go into Vehicle Data.

 

Car fixed, that was fast.

-Bosch Alternator luckily, alternator fine condition, replaced VoltageRegulator/brushes
-New AGM battery

Total cost, lets say equivalent of 600$

 

Bang, nicely done!

 

Deltec Premium Gold
668 AGM 80Ah 800CCA

Voltage after delivery=12.77Volt
-Charge CTEC........whole day 12.77V.......................................14.42 Volt(stage 4).................
---.Next day (Stage-Green)...........13.65Volt.
------Next day(Today) Rest voltage at 13Volt........So it sit whole day at 13Volt without charging.

--------------------------------------------------------------------------
Previous experience at work with huge Glass Cells, one cell=2.x Volt.
-After many years all the cells in one town got replaced with new ones.
--Theres a lot of gassing after filled with acid.
---Connected to Rectifiers and System, theres still a lot of gassing 1 week after instalation, it seems the Rectifiers are overcharging.
-----I contacted the Manufacturer(Different that the Cells replced), and found out something we did not know=Different manufacturers manufactured different cells at different lets say base voltage/charged(Fully).
The manufacturer informed us that their cells are at 2.25Volt per cell, and the old cells were at 2.5Volt per cell, similar variations in the SG measurements(Acid).
---The selution was to adjust the Rectifiers to the correct voltage of 2.25Volt as not to significantly shorten to life of these expensive cells.
------A battery room full of charging mist=Thats a time bomb(No smoking).
-----------------------------------------------------------------------
Not sure today what is the case with all these different car batteries...(CTEK detect that I assume).

 

Deltec Premium Gold
668 AGM 80Ah 800CCA

Voltage after delivery=12.77Volt
-Charge CTEC........whole day 12.77V.......................................14.42 Volt(stage 4).................
---.Next day (Stage-Green)...........13.65Volt.
------Next day(Today) Rest voltage at 13Volt........So it sit whole day at 13Volt without charging.

--------------------------------------------------------------------------
Previous experience at work with huge Glass Cells, one cell=2.x Volt.
-After many years all the cells in one town got replaced with new ones.
--There's a lot of gassing after filled with acid.
---Connected to Rectifiers and System, there's still a lot of gassing 1 week after installation, it seems the Rectifiers are overcharging.
-----I contacted the Manufacturer(Different that the Cells replaced), and found out something we did not know=Different manufacturers manufactured different cells at different lets say base voltage/charged(Fully).
The manufacturer informed us that their cells are at 2.25Volt per cell, and the old cells were at 2.5Volt per cell, similar variations in the SG measurements(Acid).
---The selution was to adjust the Rectifiers to the correct voltage of 2.25Volt as not to significantly shorten to life of these expensive cells.
------A battery room full of charging mist=That's a time bomb(No smoking).
-----------------------------------------------------------------------
Not sure today what is the case with all these different car batteries...(CTEK detect that I assume).

 

Just for New Battery info :
Deltec Premium Gold
668 AGM 80Ah 800CCA
-----------------------------------Delivery------------------------------------------------------------Charge----------------------------------------------------
-Charge CTEC........whole day 12.77V(2.12V per cell).......................................14.42 Volt(stage 4)(2.4V per cell).................
---.Next day (Stage-Green)...........13.65Volt.(2.27V per cell)
-------------------------------------------------------------Vehicle not used--------------------------------------------------------------------------------------
-Car stand for 5 Days uncharged.
--Battery Voltage=12.88V
---Thats is 2.15Volt per cell

---------------------------------------------------------------------------------Info about Deltec----------------------------------------------------------------

Origin of Deltec Batteries

Deltec Batteries is based in Australia and New Zealand.
The company specializes in manufacturing and distributing a wide range of battery products, including automotive, marine, and industrial batteries.
Lets see how this plays out compared to a Varta over time
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
The Deltec Premium Gold 668 AGM battery typically has a lifespan of 3 to 6 years.
However, this can vary based on several factors:
Usage: Frequent deep discharges can shorten lifespan.

• Maintenance: Proper care and monitoring can extend battery life.
• Environment: Extreme temperatures can affect performance and longevity.

Voltage Per Cell After Charging
AGM batteries, including the Deltec Premium Gold 668, generally have a nominal voltage of

2.0 volts per cell. After charging, the voltage can rise to approximately 2.2 to 2.4 volts per cell.

 

5 to 10 days is hood - Don't let your battery drain unless you have no way to prevent it.