DEad battery in 12 hours?
 

So my wife's 2013 C250 has been fine. she got home last night about 10. This morning when she went to use her car, the battery was bone dead! Not a light, dash light, dome light, click when trying to start.......absolute zero. MB roadside assistance came out this afternoon. He jumped the batt and it started up. Idled about 10 minutes, turned off and tried to start, but batt was still weak and cranked a tiny bit and stopped. He did a voltage check at the batt had just over 10V. That batt did not go from 13V to 10V by the AM without something draining it! NO way that batt went from fine to total death overnight without some sort of electrical drain on it. He thinks it was just the battery went bad, but that's not how a battery a behaves. Get weak with time....yes, but die the wy it did that fast....no. We will see in the AM if its fine or not. I want to bring it in to the dealer, we have a warranty on it, and let them check it, but the issue may not happen again.

If you have a clamp meter (current meter), you can see how much current draw. My 2011 C300 draws very little, about less than 100 mA. I checked it a few times in the past.
By the way, I bought 2011 C300 new in March 2011. The battery died in March 2016. It was kind of suddenly going dead. I remember I jump started it once and charged the battery by driving on highway for a while. Next time it still didn't start so I bought a new battery at the MB dealer the same as the first factory one.

I hate to say it but it sounds like a battery cell died. My guess is that the cold weather affects the battery and "kills" a cell. I have a couple of vehicles whose batteries both died this winter. They both had the same symptoms you described. I charged them up to 13v, then overnight it would drop to 10v. If I charged the battery then tried starting the car without the charger hooked up it would only crank once then the battery would die and read 10v. I thought the same thing as you, there's no way a battery could just fall flat on its face overnight without a major battery draw. Sure enough, I took the batteries to the auto parts store, they tested both of them and said that they both dropped a cell. I've had to replace the battery in two of my vehicles this winter for no reason (luckily both were exchanged under warranty as I replaced them 6 months ago). Now that a new battery is in both of my vehicles (2010 Corvette Grand Sport and 2003 Hummer H2) they start with no issues, even after sitting for a couple weeks.

The expected lifetime for a battery is 5 years, and being that your wife's car is a 2013 it is on its 5th year. It could be that the battery is old and needs to be replaced. Hope this helps.

My experience with 2 new batteries some years back. I was building a generator with auto cutoff to engine for my uncle on farm, I used two of my own good batteries to calibrate-Everything worked fine. After completion I went & bought two new batteries. Connected I found the engine cut in just before it suppose to get to a stop by calibrated auto cutout cct.
Put old batteries back, no problem.Both batteries cranked my then small car ok(No snowing). I suspect these new batteries drop voltage too quickly, and re-trigger the cutoff cct too fast, causing the engine to run on again.
I took both batteries back, and both new batteries failed on a load test, they gave me two other new ones that pass loadtest 100%, all tested good.
The lesson from this is how many "faulty" not 100% up to it, is sold new, then last only a few years-?.
If it was not for this little experience, I would never thought about a battery in this way.

This batt appears to be the original. It seems strange to me how this happened. I'm in Vegas, and not real cold and car in my garage. oh well. I'll see how it is today and hope for the best.

Thanks for the input!

Buy a new battery, you're aggravating yourself looking for an answer that fits the way you view the world. Batteries cell fail regardless of how much you think batteries don't work that way. If you want piece of mind have the draw on the vehicle checked and the output of your alternator checked as well. Then buy a new battery since this one is not gonna cut it any longer.

Have your battery load tested if you are not convinced. Just because you do not live in a cold climate does not mean it will necessarily last longer. Hot weather can affect batteries as well. Cars today are so sensitive to have the correct voltage to be able to start. It is not unusual today the have the car start just fine one day and the next it will not start with no advance warning. Could it be something else, absolutely, but going by your description of the situation, the battery seems like the most logical, simplest place to start. Hope you get to the bottom of it soon. Please post back when you find the solution.

Ha! Same thing happened to me. I bought a used 2011 C300 (in 2012) the battery died shortly after and I had to buy a new one. Wut? :nix:

The batt was changed when the MB roadside guy came out. Car has been fine since. I suppose a batt cell can just fail. I am used to the old type batteries and cars, where a weak battery still tries to work and you can hear a click, or see a dim light on, but is unsuccessful at starting the vehicle. I am also wondering if there isn't a fail-safe in place to avoid any damage to electronics when the batt does fail and voltage or amperage has a dramatic decrease or even a fluctuation. If so, the car brain would disable the system and all power would seem to be nonexistent. We have such systems in the slot machines here in Vegas. I am a slot technician, and work with electronics a lot.

Anyway....thanks for the input!

Glad to hear you got it sorted quickly.