Battery died after 9 Months




My concern is why it went dead. About once every 2-3 months the right side parking lights come on during the night. I turn them off the next morning. Dealership ran an XENTRY(?) test in Nov. 2016 for this and came back NPF.
Any suggestions.








But I agree with your overall perspective that there is something not right about such frequent battery issues. The maintainer addresses symptom only as you know.
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Seems Cen-Tech Maintainer and Float Charger at Harbor Freight is $20.
How do you keep the charger charged?
Also have a new riding mower with 12 volt battery and a pick-up I drive far less than the M-B. Can I use a device to recharge their batteries if they die or get weak?
Hate to sound dumb, but I am when it comes to this stuff.
Last edited by El Cid; Sep 30, 2018 at 04:39 PM.
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I've used the Schumacher SEM-1562A-CA 1.5a maintainer for several years now. In fact I have 4 of them, used for vehicles and riding mower. Yes you can use it for both. All have been very dependable. I had an issue some years ago with HF maintainer - it did not recognize full charge on the battery and kept applying voltage. I like the Schumacher as they cycle maintenance voltage to the battery without any problems. No overheating.
I also have 2 battery chargers/starters but I use these mainly just to jump start vehicles with low or dead battery. Not for constant connection as the amperage will be too high for long term use.
The maintainer is plugged into a 110v wall outlet and provides 12v dc power at low amperage to the battery. This will be similar to whichever brand you decide to get.




NEW story from the dealership. Rather than drive one hour to show up at dealership on a Monday AM, I emailed the service manager. He replied that the battery died because the right side parking lights were coming on all the time. Called him and explained that that absolutely was not the case, but he said that they were coming on enough to drain the battery. Once every couple of months and only for a few hours?
My Nov 2009 build date model has the older switch that has both an O for off and A for automatic. Separate switch for parking lights. You can leave it on O with the DRL's enabled and the headlights come on automatically. You can do the same thing with A, but that also causes the "entry" lights to come on when you use fob to open car. As car is in a dark garage, I used the O rather than A so the "welcome" lights would not come on every time I opened the car doors.
SA said leaving it in O causes the parking lights to come on automatically? Why would it only be the right side ones?
He also said that letting it idle for two hours would not charge the battery as the alternator only works when car is moving. The Roadside Assistance guy had told me to let it idle for two hours - which I did. SA said driving it 20 miles will fully recharge the battery! Have not tried to start it as had no where to go and was going to wait for appointment with dealership.
SA said no reason to bring it in and nothing wrong with the battery or the car.
Any thoughts of the above?





I have found that low battery is indicated when the Comand system -- which I choose to leave on by default -- does not turn on when the car is started. I will soon buy a maintatiner, too.




I have found that low battery is indicated when the Comand system -- which I choose to leave on by default -- does not turn on when the car is started. I will soon buy a maintatiner, too.





Normally, when you later return to the car and start the engine, Comand resumes operation automatically... if there is enough battery charge. If the screen is dark instead, it tells me that a battery top-off is indicated. This is a more reliable "tell" than waiting for ECO Stop/Start to stop working.
My E350 shares garage space with my wife's 2014 Sonata (with original battery). I swear the Sonata laughs at me when I connect the charger to the Mercedes (2-years newer on its third battery). BTW, my C320 is 20 years old next May, and it is using only it's third battery
Last edited by DFWdude; Dec 19, 2020 at 09:54 AM.




Normally, when you later return to the car and start the engine, Comand resumes operation automatically... if there is enough battery charge. If the screen is dark instead, it tells me that a battery top-off is indicated. This is a more reliable "tell" than waiting for ECO Stop/Start to stop working.
My E350 shares garage space with my wife's 2014 Sonata (with original battery). I swear the Sonata laughs at me when I connect the charger to the Mercedes (2-years newer on its third battery). BTW, my C320 is 20 years old next May, and it is using only it's third battery
My other vehicles are a 2014 Nissan Rogue (great vehicle) and 2011 Toyota Tacoma. Rogue still on original battery and had it checked last month - OK. Replaced the Tacoma's at 6 years since I seldom drive it.





When I say "asleep" that means the car has to be left undisturbed for a period of time, doors closed , etc so all modules shut down. The small mv draw is typically for ECU memory, clock, immobilizer.
If there is a substantial draw found, individual circuits at the front and rear SAM (fuseblocks) can be then checked to isolate the circuit with the draw. PowerPoint.com has a good chart correlating mv to amps but you can also use an ammeter for determing draw.
Might be that there's a module that stays on - it will test fine on a scan because it's functional. But if it never shuts off it will pull the battery down.





Bottom line... the car will always start and operate as normal. And, it can sit for a couple months without issue. The difference is that the Comand Audio System (radio, media, phone, nav, etc) will indicate battery state if it doesn't turn on automatically when the engine is started.
I can't imagine many folks purposely turning off the Comand System before parking and exiting the car. Soooo, it should be on when engine stops, and return to on when engine is restarted. If you haven't noticed this yet, you might check next time...
Last edited by DFWdude; Dec 19, 2020 at 10:59 AM.




So, at least once every two weeks I go on a 20-30 minute drive through the countryside if I have not driven the car lately.
Recently Consumer Reports had a brief statement that due to Covid-19 people need to drive their cars once per week for 20 minutes or more (if I remember correctly).
In past 12 months, I have only put about 1,000 miles on my car. So far, it starts when it should. Temp was 29 yesterday, but naturally warmer in the garage when I started it at 7:30 AM.
Interestingly I am taking car in on Dec. 31 for annual service.





This unit has quick disconnects with waterproof caps (for two cars if used with imagination) and includes cross polarity protection that the $10 HF doesn't have. I plan to install the quick connect to the back edge of the hood, ahead of the starboard wiper.
I can see spending $25 or so for this, but I'm not paying up to $100 that places want for the ctek.
Last edited by DFWdude; Dec 19, 2020 at 02:26 PM.






Last edited by DFWdude; Dec 19, 2020 at 02:23 PM.


