How long before battery dies if not driven?
 

Gotta travel for a couple months. Neighbors will have access to my keys in case car needs to be moved. But they may not be available to start it up periodically.

Will the starter battery die if it sits that long?

If I have wifi, I could start it myself via Mercedes Me from anywhere in the world, no? (Garage is well ventilated, and I could do it when no one’s around.)

Has anyone here tried that? How long between starts? Recommendations for or against?

Best of putting it on a battery maintainer if you have an outlet. I get a battery partly charge reading after a week with no maintainer and after two weeks I get a battery critically low message. A battery maintainer is your friend with these cars no worries when it’s hooked up and hooking it up is very easy.

Just my $.02:

Buy a trickle charger. I have one that plugs into the cigarette lighter. Very convenient.

FYI, I have been using one for my 2008 Boxster and the present battery is 7 years old and still works fine.

I recommend chargers made by CTEK but there are other good companies out there.

Here is a link: https://smartercharger.com/collections/vehicle

You can set the car to turn off access to the battery while away for an extended time. I did it once and it told me how long the battery would last in the disconnected mode. You can buy a battery tender (trickle charger) if more time is needed and save the battery from fully discharging which is not good for the life span for the battery. On my wife's Lexus RX the battery is in the floor in the back and I have it hooked up all the time and just plug it in when needed. The MB has a more exposed connection point so that might not be ideal to leave it on the car full time.

Thanks guys, for taking time to answer. I do own a trickle charger but wouldn't feel safe using it in this situation. It's a condo garage -- lots of foot traffic, workmen coming and going during the day, etc. The electrical outlet is 20 feet from my car. Using it overnight when I'm home is fine, but not when I'm away for two months.

I like the idea of learning how to shut off the car's battery access. Problem is, if anybody needs to move the car, they won't be able to.

Any thoughts on remotely starting the car in the middle of the night every couple of weeks, and letting it run for 10 minutes or so? Would that work?

Funny thing is, my wife's Lexus RX battery has always survived these long trips with no problem. The battery on my previous car, a Lexus GS, died every time. The Lexus service rep suggested I buy a $600 motherboard replacement that "might" fix the problem. Yeah, right. Instead I bought a Triple-A replacement battery under warranty for something like $39.

Check your manual: there's a setting to extend battery life if you will be parking for long times. I've used this for 2 week vacation airport parking. Be aware that this battery savings mode deactivates the alarm, and also the mercedes me remote access features. The bonus is that with a fully charged battery the car estimates anywhere between 22-26 weeks parking is OK. I've no idea how reliable this is. As for the alarm deactivation: I figured car was probably OK in an airport parking lot ...

You didn’t say what car you have. If it’s a 2018 up e class the standby mode can be found in the menu I believe under system. You will see it. I never tried it. I always just use the maintainer but I can understand in your situation my you don’t want to do that option. To others who answered a trickle charger is old tech. A maintainer is the way to go. There is a difference. The maintainer goes into standby and charges in blasts. The trickle charger is always lightly charging. I believe any newer battery tender is classified as a maintainer.

Dear 2012 Merc amg:

The CTEK trickle charger, see post #3, does not constantly charge: Constantly charging a battery will fry the battery.

Any good trickle charger will turn on and off: it monitor's the voltage of the battery and charges when needed. The CTEK above does this.

Schumacher Extender $25 on amazon.
 

Here’s what I use.
https://cimg1.ibsrv.net/gimg/www.mbw...b2133cb9bd.jpg

You can charge a battery via the cigarette lighter? How is that possible?

It depends if the cigarette lighter is still powered when the ignition is off. I think in previous models, you could set it so that the cigarette lighter was on by switching the position of a fuse.

Instead of having to open the trunk and hook up to the battery, a pain in the as*, you get one that connects to the cigarette lighter. Our Boxster is not used on a daily basis. The charger with monitor is used while the car is in our garage. When we use the car, we unplug from the cigarette lighter. When we return we plug in again. The battery is thus maintained.

Without the charger, after 9 months we had to replace the battery - there times. We got in touch with Porsche. Under warranty they replaced two batteries. They refused on the third. They said we should be using a trickle charger. They sent us one, made by CTEK free of charge. I replaced the battery with one from Auto Zone. That was 6 years ago! It is still working fine.

Here is the link to the battery charger: Note it is made by CTEK: https://www.prestigeimports.net/tric...ry-maintainer/

Make sure you car actually has a 12v (cigarette lighter) socket. My 2018 does not have a 12v connection. It has 115v connection instead.

There are charging posts in the engine compartment.

The dealer told me there is a "standby" setting to curtail battery drain; I believe there is something like that for the key too. Parking for extended periods and instructions on how to activate standby are on pages 146-147 of the 2017 manual.

https://cimg1.ibsrv.net/gimg/www.mbw...d8bfb7830b.jpg
https://cimg5.ibsrv.net/gimg/www.mbw...6bde0d809a.jpg
Dear ua549:

In my 2019 E450 there are not one but two 12 volt receptacles that you can insert the battery charger:

1. One is the foot well of the passenger side just below the glove box;
2. The second one is in the center console for the rear passengers

I have attached photos of each.

Those are not in my 2018. I asked the shop foreman if they could be added and was told no.

Standby mode is described on page 157 in my 2018 operator manual.

https://cimg2.ibsrv.net/gimg/www.mbw...90aae80f1e.jpg
https://cimg3.ibsrv.net/gimg/www.mbw...de4332cc30.jpg
https://cimg7.ibsrv.net/gimg/www.mbw...15bd1a62af.jpg
While I'm sure well intended and even informative for those not knowing much about their cars (there're more than some here, based on staff posted), the info, repeated in several posts, is useless for any charger/maintainer purpose because MB's sockets are dead when car is not powered. The only way to connect is directly to the battery or charging posts - both are under the hood.

That loud wailing you hear is the sound of the siren on the Internet Police cruiser that's about to pull y'all over for runaway Thread Hijacking. :)

Seriously, though, thanks to all who mentioned Standby mode. My 2019 coupe does have it, and I'll look into it further.

No thoughts from anyone on the advisability of just remote starting the car from afar every couple of weeks? Would that keep the starter batter charged?

Just a bad idea in general. There are stories where people ran gas generators in their garage and were overwhelmed by fumes and died just from opening the garage door.

Thanks, but as mentioned earlier in the thread, it's a condo garage, extremely well ventilated. Fumes are a non-issue.

What I'm eager to learn is:

1) Would the car reliably start and stop via the Mercedes Me app from a foreign country as long as I have wifi?

2) Would running it at idle for ten minutes or so every couple of weeks keep the starter battery charged, or would it need to be driven to keep the starter battery charged?

Just idling it ten minutes would not do much to charge the battery, Alternators really are not meant to be chargers, they are more or less there to maintain the charge of the battery. To do something measurable ya, you'd have to get it out on the highway at 2000 rpms for an hour or so.

Mercedes me is not very reliable. I wouldn't count on it. Depending on where you park cellular signals may be unreliable as well. BTDT when trying to locate may car in a large airport parking garage.

Thanks, merc. That's what I was trying to understand. So the common practice of people away on long trips having friends start and idle the car to keep the battery alive is just a waste of time, right?

It's sounding more and more like Standby mode is the only reasonable option.

I would normally recommend CTEK, but you make a good point about your situation and length of time away. Plus, my CTEK has kind of gone in the crapper and the Mode button seems messed up, so not 100% sure the unit is working correctly...pretty disappointed in the quality, since I don't use it that much and it's only a few years old.

Anyway, go the "Standby" route...or rent out on Turo for a couple months. :)

Turo! That's the ticket! :)