I drive a 2011 E550 to work (5) days a week.
The drive is only 10 minutes each way - some at highway speeds, some at urban / rural speeds.
Not many longer runs to meetings down town or to the airport.
With this driving pattern + COVID working from home 2.5 months earlier this year ... I think the draw on the battery has worn the battery charge down.
To the point the car would not turn over to start yesterday morning.
AAA came out to get it going with a boost. Then I drove the car at highway speeds for 1/2 hour, keeping revs up. Which seems to have recharged the battery.
My question ... will shifting manually - keeping revs higher on these short trips (say at 4,000 rpm) help to keep battery charged?
I do not have a trickle charger.
The car cruises along at just over 1,000 rpm when in drive. So 4,000 rpm charges the battery 4 x better?

 

I don't think it makes a lot difference how fast you turn the alternator. It is designed to give enough voltage with idle and unless you pull some extraordinary power I don't think you need extra speed.

 

You should just go pick up a battery charger at Walmart. They're not that much, around $35. They used to be $20-$25 on Amazon for an 8amp charger which is enough power to fully charge up a battery in a few hours. But now Amazon wants $45. That's pandemic pricing for you. Don't count on the alternator to fully charge up the battery. It only does the bare minimum. Previous models charged it up, but it seems the modern cars don't fully charge up the battery because you get better gas mileage if you don't. But of course it does kill your battery earlier but they don't care about that part. So you should put the battery on a charger once in a while because a fully charged battery lasts longer than a partially discharged one.

https://www.walmart.com/ip/Schumache...rger/868567776

 

First... How old is your battery??? You shouldn't have to drive with the car revving up like that. As it was mentioned, even at idle the alternator should put out enough to charge the battery. Maybe it is just time to replace it?

 

.
Hi Chris,

I do not know your 2011 E550 charging profile, but my 2014 E400 is as below


When voltage is 12.75V, that is zero charging.
When voltage is between 12.75V to 12.50V, that is car on purpose eating battery power mildly
When voltage is between 12.50V, that is car on purpose DRAINING the battery. ...eco mode bullsh-i-t I think.
Above 12.75V is all charging.

The problem is, we do not know exactly when the charging/discharging algorithm decides to do midly discharging and DRAINING. Surely after battery deemed as decently charged.
But how the hell the algorithm can predict how far we will travel at that point in time and making sure battery is at least 80% charged anytime we kill the engine.

If you see the speed in KM/H, that shows my car was idling a long time at the beginning.

What bothered me is the 800 ish to 1240ish region of the voltage data points.
Thats when the DRAINING occurs the most and that could be your short drive region/time-frame to the office, assuming ur E550 charging/discharging profile is the same as my ECO Start-Stop equiped E400.

Allowing by battery voltage down to 12.25V is a big NO-NO if I were the engineer at MB.
That is big deficit or near to 30% battery state of charge only, assuming if the load taken from battery is only 5 amps-hour
If the draining is high like 75amps, hitting low 12.25V will happen in few minutes and does not represent 30% state of charge,
but represent voltage drop from high current draw.

Anyway, my battery , I charge it every other day or latest once per 3 days when not being used. 5Amps CTEK with DIY fan cooling for the Cetrek.
The chances that my battery is not at least 90% charged by the car algorithm at the time I reached home and shut down the engine.......is VERY HIGH. In the name of "green" or ECO MB way
So the CTEK charger is my best friend.

All Logs using Torque App with OBDLINK LX bluetooth

Happy troubleshooting.

 

I should have mentioned about this in my first post in this thread but I think you need to look into replacing your starter. There are some writing about this like in the below link and others.

https://mbworld.org/forums/e-class-w...ong-crank.html

 

2014 has smart charging (although I would disagree) when
2011 does not.Quite different animals.
HF sells battery maintainers for $9.99 or 6 bucks on sale. No excuse for not having 1

 

Just replace the battery. My car sits for weeks at a time and starts right away. having the car sit should not make the battery drain all the way unless the battery is weak. If it is more than 3 years old replace it.

 

The real answer is to get the battery load tested and see if just needs a charge or if it's just too weak to hold one for long. Most auto parts stores will do it for free. If it's just discharged, charging it up is much cheaper than a new battery.

 

It was well known that the Eco minded battery charging was hard on the battery, but fascinating to have some real data from @S-Prihadi regarding the behavior.

It makes me imagine that the fuel and emissions savings from this charging scheme can’t possibly outweigh the cost and environmental damages of the resultant frequent battery replacements. Then again I sometimes feel that certain systems on luxury cars in general are only designed to last the lease period anyway...

 

Yes overall that's probably true. However once you factor in CAFE, those factors aren't considerations. Basically the better your fuel mileage, the more credits/lower fines you get. So every trick in the book to increase gas mileage gets used including not charging the battery. They didn't do this in the W211 and I still have the original battery after 12 years.

 

Get a new battery , see how it behaves... if you still have issues with starting , replace starter.
dealer have done it for me back in the day under warranty , and once i had to replace it at indy shop.
So far so good for a few years.

Or atleast , try to get a battery tender maintener , or what i did , got a dewalt 1.5amp charger from walmart years back. Takes a little longer tham a 8amp one but does the job. 10 550

 

I am not sure if that is new charging system, or poor quality of AMG batteries that are put in those cars.
Both my 2014 W212 have flooded batteries and 1st come with the car 3 years ago, still holding good charge.
My 2017 Ford truck had not so smart charging system and both batteries in it died promptly at age of 3. They were disconnected for the winter and under separate battery maintainers. 1 had slightly different death symptoms than other, but both were junk.

 

I have stopped investigating my E400 charging algorithm for quite sometime now. I have come to term with it ...Amien.
Before I have the Torque Apps and OBD2 bluetooth, I video the dashboard screen and set Amperage and Voltage.
I have an alternator behaviour video of 43 minutes, during a use, which I sped up to 12 minutes, but I doubt u guys wanna watch something that boring
I have attached a TEXT file showing what happened, faster read that way. Charging Profile 43 minutes drive 25apr2019.txt

Some teaser photo below of the alternator charging video :






Prior to MB dashboard amperage + voltage info, I use my stand alone amperage clamp and voltmeter and idle the car for like 15 minutes and do engine stop and lock the door and log what consumptions before car computers
really sleep till lowest amperage drain occuring.

Too bad the Torque Apps can't pull out amperage data but anything less than 12.75volt while engine is running = a discharge condition, easy to summarize.

I have accepted that my E400 has a charging algorithm which will result in my car battery unable to live its life to the fullest, as per my car driven habits.
Knowing how a battery works, I have decided that the only way to solve this is to use a small battery charger, whereby I will keep my battery fully charged at least twice per week.
Anytime a battery is not fully charged, sulfation occurs. That simple. CCA is lost when sulfation on the plates gets more and more over time, where charging can no longer remove it.
You can read 12.7 volt unloaded at the battery thinking it is healthy, once you apply 200 crancking amps and it won't spin the starter beautifully and voltage sag down to 9 volt or less,
that is CCA decline.


However, one must also understand when is the proper time to charge :

01. After/while cleaning the car with long duration of doors and boot/trunk being opened. Lots of electronics of the car wake up at this stage, not indoor lights alone.
So, after washing or cleaning the car....or anytime I mess with the car with lots of time I spent in the interior with doors opened......... at night the battery will get charged till next day.

02. Temperature. I will only charge the battery once the battery has reached stable room/garage temperature. Charging accuracy or stage of charge accuracy is temperature related.
So usually I opened up my car hood/bonnet for many hours before I hook up a charger late in the night.

03. If anyone uses a 5 amp CTEK or bigger one, do know this. This charger is okey but runs hot 50C or so, due to all plastic construction, for me at 30-31 C ambient temperature.
So cool the charger, make it live long ( save us money ) and gets its voltage accuracy to be at its best. Yes, again temperature does play an effect, albeit the CTEK 5 amps does not have a temp sensor
for the battery. CTEK interconnect terminal is poor design, it runs HOT too 50 C or so, at least on mine. 5 amps only and interconnect gets hot, that is poor design.
I can't find my thermal cam photos sorry. I usually like to explain/show with evidence.


04. Maximum charger size for lead acid or AGM, keep it at max 15% of amp hour rating.
If 100 Ah battery, 15 amps max is the charger and 3 stage at least, 4 stage better and must have float mode ( maintainer ).

05. 5 amps CTEK is good enough for up to 120 Ah battery as long as it is only for charging and not as a power supply when doing works on a car and needing DC power as to not drain the battery.



SUMMARY

S1. My E400 charging profile I can't say it always the same eveytime I logged it, pertaining to its first 15 minutes from engine start to car moving.
So I gave up logging it

S2. If you want to know that your car battery is not fully charge or at least 80% charged that day after a day use...easy.
Open hood when you reached home and not using the car for at least 10 hours later. Lock the door and keep that key far away to not trigger radio communication with car. Don't do anything which discharge the battery.
Get battery to room temperature after approx 4 hours ( for me ).
Measure battery voltage with a decently accurate voltmeter.
If you read 12.45 volt or lower, there you go, your battery is probably at 60% state of charge.
What we want to see is 12.65 to 12.8 volts during overnight storage 4 hours after engine shutdown and zero activities eating battery power.

Happy troubleshooting.....

 

My only additional notes to the above is that those state of charge charts typically refer to no load voltage. There's typically a slight current draw when the battery is connected. Also it's temperature dependent. Typically that voltage is for a battery at 70 degrees. I've registered 11.5 volts on my battery when the temperature was in the 20s in the winter.

 

Checking chemistry status in battery by measuring voltage brings huge error margin.
I have load tester and Solar digital gizmo for testing CA. Between the 2 I can figure out how good battery is.
Than modern electronic chargers often have desulfating mode (disconnect from the car as it runs high voltage). When battery is marginal ,the procedure can restore it to usable status.

 

Agree, me forgot I am in a tropical country with no cooler than 28C 365 days a year and you guys have winter. Thanks C.
After 4 hours or when all electronics are sleeping ( usually 30 minutes) my car consume only its so small stand-by needs at 6 milliamps. Car key far away, door locked, hood open.

Forgot to add, there are times which I can't yet pin point the exact cause ( occured twice already that I know of )....but I suspect is a long good hard run where my aircond runs very cool for X ( good ) amount of time
on the road at decent speed ( not in bumper-2-bumper traffic jam ). In like 30 minutes later after engine shut down, the aircond blower will spin slow for some minutes. I did not record the amperage discharge
for this but I think 1 ampere is easy. NO, the interior aircond control panel did not show anything as active nor does my car has that special button called REST.
I suspect this is a way the car remove more condensation from the indoor unit ( evaporator ) to keep away growth/mildew. It can only be seen if I remove the air baffle on top of battery box. It is so quiet the slow spinning.

 

Sweet, what brand and model is that gizmo K ?
Yes , for those who really wants to know his battery state of charge in depth will need some sort of timed load, but that might be too complex for most and our car is 1 single battery only, unlike big yachts or solar panel application where battery $$ is high.
I usually use one or a few 50 watts 12V halogen bulbs to simulate load for X amount of time and to remove surface voltage. But rarely I do this even for my car battery, only on suspect battery.

My Varta AGM does not reccomend desulfating mode to be performed on it. The OEM battery for my market is also Varta in MB own sticker.

 

For testing, that is new gizmo.
I just tested 2 yo flooded battery since I pulled it from sedan for use on the boat.
1000CA rated battery shows 1210 CA (it was over 1300 when new)

 

A small handheld battery tester is a must have for anyone who is OCD about keeping their auto batteries healthy. Foxwell and Ancel also make some inexpensive battery testers. If I didn't already have a Solar BA9, I'd pick up the Ancel BA201.


Combine a battery tester with a good battery charger, that can de-sulfate a battery, and you've got a system to keep car batteries in good shape, and thus reduce the stress associated with unexpected battery failure.

 

That is still not the same as the no load voltage of a battery at rest. I left the fog lights on once and killed the battery, brought it home to charge up and tested the voltage and then put it back in the car. Voltage was about .3 volts lower with it connected than the no load one. Granted it had a slightly higher load on it as the display was just on. According to the charts, about .3 volts is almost a 30 percent difference in terms of state of charge.

 

Voltage drop reading with load will depends on how big the load is and how weak your battery is if it is not totally healthy or even if the battery is totally healthy drawing certain amperage will drop its measured voltage.
Automotive battery is a standard 20 hour discharge to get the Amps Hour Rating, so in theory a 100 amps-hour battery is discharged at 5 amps and they calculate to the minimum voltage of 11.9V if I remember correctly.
Same 100Ah battery if discharged at 10 amps will not be a 100AH battery, it could be 80ish AH, depends on the test result.

What most people dont know is the amount of power draws by the car electronics from engine running to engine stop, locked the car and leave the car till all computers really sleep at least 30 minutes later.
After door locked stage, my E400 is about 6 amps draw for about 30 seconds. Then it will be about 3 to 2 amps for about 5 minutes.
After engine shutdown and if you leave the car key in ignition* ( *maximum left position ) where the dashboard still shows gauge mode, that is 11 amps worth of power draw.

Hence my suggestion for those who wants simplified version is to check battery voltage is after about 4 hours or when room temperature is reached and car computers are sleeping and very very low
amperage draw, as such it will not create significant voltage drop when one measure battery voltage.

If that Solar BA9 battery tester is nearly as good as say Midtronics battery analyzer unit, perhaps once in a while test the battery with it.

For me, knowing my E400 charging algorithm is basically a battery killer, all I need to do is charge the battery at such low power a 5 amp CTEK is.... twice per week at least and be happy and
hopefully can get 4-5 years out of the Varta AGM. By now my ear is trained to hear battery getting weaker just by the sound of the engine cranking and the speed of crank to engine active/running,
as such there is never a car of mine ( my own daily drive ) which in my last 25 years ever had a battery failure, I will replace it the moment the cranking speed and sound is out of spec.

I dont have winter in my country, so basically I don't have experience by ear to detect reduced crank speed due to say zero Celcius ambient temperature.

 

If you think the short drive to job and back is not enough to keep your battery charged you could try the fog light “trick”.

I don’t know if this is the same in your car but in my 2010 E550 the battery voltage jumps up to 14.5-14.7 V when I turn the rear fog light ON.

My my light switch is the one you have to pull out for the fog light meaning I will have head lights ON before I engage the fog light. Just driving lights don’t increase the voltage from 12.7-12.8 V but as soon as I pull the switch out for the fog light voltage jumps up. Have tested this numerous time while driving on highway and every time it does the same.

This is trick could help charge the battery a little better but I feel you should not need to do anything special even you drive short distances. I think it is your starter draining your battery like it did mine and after starter change no issues st all. Just yesterday drove the car after it sat 4 straight weeks with no use at all and it started up like a new car does.

 

1.5 weeks (say 7 days driving to work) after the first boost required ... I drove to work ... then 2 hours later when needing to leave for airport to catch a flight - not enough juice in the battery to turn the starter over.

The car is currently at the shop getting a new battery & a check on other related problems.

i will look into getting a trickle charger.