$100 GUY

Hey guys,

So, I have the following situation with the 12V battery:

I start monday battery ok, of course not entirely ok with the MB smart charging system we got in our cars, but at least with 75% State of charge, and by saturday the battery has almost no charge at all.
I use the ctek charger on the weekend, get it back up to a 100% SOC, even staying in the float mode for a while, and then it the cycle starts all over again.
Once again, I have to recharge it. This has been going on for about two weekends.

What is going on here, what can I do? Battery has about 9 months only.

Mud

Aside from a possible parasitic drain, did you verify that the battery is being charged correctly by the alternator when the engine is running?

$100 GUY

Well, since we have the MB smart charging, it really does not like to do it like other cars, but yes, I think is working well, because at the end of the week, for example, by friday, before I use the car, it says something around 11.8V, and afterwards it goes up.
Or by Saturday, when it is almost at 0%, 10.6V and it starts, after a drive, it goes up to 12.3V when I turn off the car. And then I have to use the charger.

But, by that day, it really starts to go downhill faster.

So, today I used the car, after being full charged yesterday, when I left was at 12.4V and when I turned off the car was at 12.5V. So yeah, pretty good numbers at the beginning of the week, and after using the car. That has been the case so far all these weeks. You start the weekend really good and by saturday, no charge. Even thou I use the car everyday.

Now I am turning off the radio besides the A/C before I turn off the car.

thefisch

Definitely need to check the alternator just in case. You should see 12.6 to 14.3v while running depending on the load sensed by the alternator.

If you garage the car, you could check for overnight drain by popping the hood and checking voltage in evening after charge has settled (let it sit for an hour after opening door to pop hood). Don't fully close the hood so you can check in the morning without opening door to drop voltage.

If no issue with alternator output voltage or drain, then it could be a bad cell. Where did you get the battery? Hopefully it is still under warranty. I would get it load tested at an auto parts store, ideally the one you bought it from. Pull the battery and take it in so they can bench test it under load. That will expose any capacity issue.

ItalianJoe1

Could just be a weak battery. Car is still under warranty?

$100 GUY

Hi there,

the values I have referred to are before starting the car, not while running.
So, I could be starting with a very low SOC and after a few miles, the voltage goes up when I see the numbers after I turn off the car.

When the SOC is in good shape, it seems the battery holds it own well. I mean, I know after a few hours in the same day, it will be good when I get back to the car. Or from the night before to the next morning.

The issue starts to happen when the SOC after a few days in the week, starts to dip into low percentages, like 12.0V and downwards. From there, it seems like it likes to lose its charge easily. I get it back up driving, but now it will get to the point, where I know plugging the charger would be necessary.
Is this a symptom of what? A bad cell?

The only way to bench test the battery is by removing it ? I would love to know if the battery has a bad cell without having to remove it. How long does it take to bench test it?

I can charge the battery really well with the Ctek, and this device would also tell me if it cannot hold the charge, but it passes that test too.

I know that when I bought the battery, when I put it in the car and read the voltage value before starting it from the first time, it said 12.4V. So it seems to me that probably that battery had been in the shelf for a while, didn't came at an optimal state and of course, with our car's system, it never got to a 100%. Is that a logical reasoning or all batteries give you a 12.4V value at starters? You guys tell me.
As far as I know, when I take off the ctek after it has reached the 100%, go to the menu of the car and it has said 12.9V, then in seconds, 12.8V.

thefisch

The voltages I suggested were to test the alternator. When the car is running, the voltage at the battery reflects the system voltage being output by the alternator. If you see swings in the voltage or it is not at least 12.6 volts, then you can suspect the alternator. But if the alternator was bad, you would probably lose power while driving as the battery only holds so much juice. And batteries are cheaper than alternators so it's an obvious place to start.

Since yours doesn't seem to start the car after a few days I am questioning the amp capacity. These AGM batteries tend to die a slow death. My old one would start for days in a row and then not start after listening to the radio for 5 minutes with the car off. It made no sense why it would work sometimes and not others.

To really test a battery, you need to test it disconnected from the car so the interior lights and other draws do not effect the voltage. But voltage doesn't start the car, amps do. To check the amps, you need to load test it and that takes equipment. Assuming a store isn't busy, a load test should just take a few minutes. You can always call ahead and ask so you know what's in store.

And I would assume a 9 month old battery is under warranty. When I was shopping, most of them cost with a year free replacement and up to 3 or 4 years prorated.

KEY08

Listen to Fisch. More than anyone on this board he has been through this battery rodeo and is providing great advice. A 1 month battery can have as many issues as a 3 year old battery.

$100 GUY

Yeah, thanks for the help.
Do I have to strictly remove the battery out to bench test it?
What is that procedure? Is it done with an electronic load tester?
What tells besides the voltage value, something like amps, bad cell?

So yeah, it seems that if it has been able to start the car almost completely discharged, you would think the amps are pretty good, right.

Yeah, I have read other threads and this kind of stuff has happened to several other members with the way our car's system treats our starter battery.

thefisch

I just like a bull in a rodeo, that battery kicked my a$$.

Bench test means out of car - actual bench not required. That way no connections with car are interfering and nothing you are doing can damage car components. Most auto parts store will not charge or load test a battery connected to your car due to possible (however unlikely) component damage. I wouldn't let them do it personally. I pulled my battery in a pep boys parking lot for them to test.

A load tester is used that can measure amps and place a draw so you can see how the amps drop. I would get the test done at the place you bought the battery so they can replace under warranty and it saves you a second trip.

Battery replacement is the cheapest option and if it works you are
If you're 9 month old battery doesn't have a warranty replacement option, then I suggest you shop elsewhere for the next battery. Just to be clear you did buy an AGM battery with the same or more CCA than stock, correct?

The G Man

Have a mechanic check our alternator, if the alternator is ok, you have a higher than normal current draw when the car is off.

$100 GUY

Ok guys, here is an update.

Since the last date, I charged on the weekends, and everything was pretty good.
This past Sunday, charged it, went to a battery shop on Monday, and the battery was in perfect shape, even showing 1000 amps LOL. He did the test with the headlights on, starting the car up, and testing the alternator, which performs great.

Ok, I talked to the guy about everything that has happened, and we agreed to check it out once again, sometime on the weekend. I used the car on Friday as usual, and until late Saturday went to check it out, saw 11.8V, turn it on, and left it idling for about 15 minutes. Did not use the car anymore nor charged with the CTEK.

So, today, in the afternoon, had 12.0V, turn it on and went to the battery shop, with around 15 minutes of driving.
The battery was again great, the generation of current great, even we left for a little while the high beams on with the car turned off, and everything was fine. The value dipped to only 10.9V when you turn on the car and they see what is going in those 15 seconds or so, I believe that is the load test. The difference this time was that the amp value was 720.

By the way, with the CTEK, I have gained more than 700 hours more of battery life, so it is money well spent for everyone, specially us LOL. The only thing that I leave plugged in, is a device in the glove box for music. I leave the car with the radio shut off anyways most of the times.

What say you guys?

kajtek1

Something is not right with the numbers. Where did you take the measurements?
The cluster routinely shows 0.5 v less than battery clamps.
Point is that 12V is deeply discharged battery and the car should not even start.
Even 12.5V is marginal, while 10.9V is DEAD

thefisch

voltage does drop when putting a load on the battery like when starting the car. The voltage should recovery when the battery is not in use. The fact that the amps had dropped to 720 on the second test when you didn't use the charger gives you a better picture of how the battery is doing on its own relying on the car. For these cars you really need 800 or more amps to crank the car up reliably.

You can keep chasing your battery problems if you want and charging it on weekends to keep it going. Eventually if will give out but you may get many more months out of it.

When they test the charging system with the headlights on, AC cranked up, etc. that is a load test but it is a load test of the charging system, not the battery itself. When the battery is connected to your car and the car is running, you are getting results of the whole system. If you really want to test the battery, you have to take it out of the car and test it under load without an alternator or charging system helping it out. Then you can see how it recovers and holds amps. That's when you will really know how well the battery is doing.

Maroc_Specops

running car between 13.5 Volts til 14 Volts

Not running healthy battery gives somewhere around 12.5 volts

Check Alternator, or Battery is bad

gl pal

Sunnyslope48

Just to be absolutely precise, "bench testing" need not be done with the battery out of the car; it only requires that at least one of the cables be detached from the battery (so that there is no complete electrical circuit that includes the battery). Whether it's in the car or out of the car is not the important consideration. Of course, it it's out of the car, it's EXTREMELY unlikely that there is anything else attached to the battery, right?

thefisch

Yes, it could be left in the car assuming you have the equipment to bring to the car for the test. If you go to an auto parts store, they likely have the load test equipment inside and would need the battery carried in.

I would disconnect both cables to be sure the battery is isolated and that any load from the test does not effect other connected components. Take the same precaution if you recondition the battery or use a charger with more than the recommended voltage per the car's manual.

$100 GUY

Update:

So, since June 18th of course I had to once again charge the battery with the CTEK because it went to highly discharged levels as usual.

Ok, all pointed to the battery, so I ordered a new Mercedes Battery from the dealer yesterday, and all was good until I discovered something.

The battery that arrived had the part number 001 982 80 08 26, and had a manufacturer date of week 14, of this year. Ok when I started searching for info, noticed that the old part number of my battery was 000 982 21 08, and that has been replaced by 001 982 81 08.
So, see the discrepancy? Funny, when I searched for this new 81 08 part, online said it did not fit my car. Huh? And when I look online for the one I received (the 80 08) I basically find nothing, and it is not the one that the online MB parts sites mention when it comes to my car, they mention the 81 08, but when I click it to see if it fits, it says it does not.

Also, the 80 08 that arrived from the dealer, which had my VIN number, says it has 70Ah and 720 amps, instead of the OEM 80Ah and 800 CCA that came with my car. So what the?

Did they gave me a wrong battery or is the new updated part number? Which has less capacity and CCA as the one that came with the car?

kajtek1

Dealer guarantee part fitment, but if in doubt- call them.
I would not worry about smaller capacity unless you drive in -20F a lot, or have aftermarket 600W stereo.

$100 GUY

Yeah, it definitely keeps the juices going for many more weeks. I mean, the battery still has life remaining, until the charger at step 5 says otherwise. This charger has been great, it is indeed a battery saver. In the past this battery would have been discarded like 2 months ago without this technology at hand.

The main problem I see with this really new battery already failing, is that it was not really fresh when it came to me and when it was installed, and that it never was fully charged before installation, nor with driving the car because of the system we have.
So, now for me and many others, it is important the date of manufacture, and if possible, charge the battery at a 100% before installing it

$100 GUY

No, my car is stock, and where I live you do not deal with low temperatures.
Ok, I will go and charge this new battery in the meantime.
I will not install it yet, because I go out of the country for several days, but the discrepancy had worried me.

$100 GUY

Update

So much for dealer guaranteed part fitment huh?
As I had worried about, the battery -despite my call to the dealer to check on the fitment- was shorter and thus did not fit well.
They told me, that in their system, appeared two options, so they sent me one of those.

But in reality, the dimensions were different, not only the values of amperage, so I had to order the new one, the same I had already said to them that came with my vehicle.

I had charged up the other battery, so whoever gets it, will be in great shape.
Both batteries lasted around 6 and half, 7 hours to be fully charged.
Not to my pleasure, but the right battery was even 3 weeks older than the battery I originally received.

And it did not give me the green light with the charger, came only in regular shape.
But fortunately, I have the ctek charger and now is at 100%
That is the main problem, many times it happens that what you get is not a battery in great shape, and you definitely think you are getting a new one, but it is not what you expect.

That, plus batteries rarely get to a 100% even with daily use, and you get the recipe for the undesirable ending: they have a shorter life.
I am glad I have all this tech and knowledge now, and for all the vehicles the ctek will play a major part in having to buy less batteries in the future!

Cheers

$100 GUY

Update

I just remembered that I have installed in my car a GPS tracking device. Could this be draining my battery?

What happens if you disconnect the battery of the car for a week, where does this device gets its energy from? Does it have an internal battery than then goes flat and then starts using the car battery as its main internal source of energy?

Someone with knowledge about this devices, chime in.

KEY08

Maybe you should speak with whoever installed the tracking device. I'm sure there is an internal power source for it since the first thing the bad guy would do is disconnect the battery, so the car cannot be traced. That would not be a very well engineered tracking device.

belarus27

Heck yea it can drain the battery... especially if its a gps , i would assume it would need a constant power to it , and if the internal battery ( if its got one) dies , it might be stealing power from your cars battery.

possibility..
unplug it and see how it behaves...
and also also the installer how did he connect the wires