TonyG3D

I know there's a constant current draw from the 12 V battery in my 2022 GLC 43 SUV (10k miles) and other modern cars, esp. in those with a bunch of remote functions, but I never have thought it would discharge the battery in 4 weeks! Now even the remote start is deactivated....

Has anybody measured the constant drain current with an in-series ammeter? Does it really add up to full capacity over 4 weeks??
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So, would it be safe to attach my 12 V battery charger to the battery before I leave for another long trip? I know these chargers are self-limiting in terms of max voltage, but does the idea itself make sense? I wouldn't want to burn down my house...

W205C43PFL

If the car is in a secure garage, consider activating standby mode. Only recommend doing this if it is in a secure garage because it disables all communications to MB servers and shuts down the anti-theft system as well.

TonyG3D

Yes, the garage is safe, but I'd prefer to maintain the connection via Mercedes me...

W205C43PFL

I see, fair enough, constantly checking the car through Mercedes Me will ping the car more often which then drains the battery, that might explain why your battery drained so quick.

Four weeks might not be an issue but there is no guarantee, anything could happen. There is always a risk of doing something, it is a matter of if that risk is worth it or that the pros outweigh the cons.

If there is someone home to check on the car with the trickle charger (like during winter storage) then it is a great option, or... maybe I worry too much and you might be fine leaving it unattended. Lets wait for those who have experience of using trickle charger unattended to chime in.

W205C43PFL

I got an idea, perhaps use a smart switch (buy one that has an app that specfically states can be controlled anywhere around the world) and install a home security camera in the garage facing the front of the car with the trickle charger plugged in, connect your smart home camera to your home network, make sure you buy those that can be accessed anywhere in the world. If you see anything abnormal, during your trip turn off the power to that smart switch. As for the security camera, just plug it in an ordinary outlet.

I just don't know if my idea is worth it, again, evaluate the risks.

superswiss

The first question here is what was the state of charge of the battery before you left? If you don't drive the car much, then the battery could be fairly empty before you even leave. I always use the aforementioned standby mode when going away on vacation for at least 2 weeks. The best thing about standby mode is that it tells you how long you can leave it parked w/o needing to charge the battery. With a full battery I get around 21 weeks with my C63. I usually charge the battery with the trickle charger the day before I leave, so it's full and then activate the standby mode. My car is mostly a weekend car these days, and I'm currently away on a trip as well. This time around it told me that the state of charge of my battery was too low to even activate standby mode. This was simply from the little driving that I do, so as usual I charged it up and then it was fine. I don't leave the trickle charger connected while away.

So, the biggest point here is make sure your battery is actually fully charged (it should say charged in the app and not partially charged) before you leave and then it should be fine for 4 weeks. Definitely will be fine if you use the standby mode. I'm not sure what you need to check on with Mercedes me while you are away and the car is securely parked in a private garage.

TonyG3D

Thanks for the replies and suggestions. I already have 4 Internet connected cameras around the house, so a fifth one would be a conch! :-)

​​​​​​I don't drive a lot, 6,000 miles/yr, but the app was showing full battery charge before I left. I wish it showed the actual battery voltage, it's such a simple add-on; I've been wondering why wouldn't MB had that functionality, since they show so many other values, including tire pressure.

My MB service advisor just emailed me that a battery discharged in 4 weeks in these cars is not unusual and suggested connecting a trickle charger--will do it in the future.

Any suggestions as to the brand of the trickle charger that is reliable and safe?

superswiss

You drive about as much or as little as I do, so I'd be surprised if your battery was actually full. A good way to judge the state of charge is to fully charge it and then see how long the standby mode says you have, and then whenever you wanna know the state of charge see how long it says you have at that moment. As I said previously, with a full battery I get 21 weeks and usually with just my normal driving it says I have about 7 weeks, so that would amount to a ~30% state of charge from my little driving I do. I have to drive 2+ hours typically to get a fully charged battery and then it gradually discharges.

TonyG3D

Thank you: I'll certainly try the standby mode which I have not tried in the past. Also, a trickle charger.

W205C43PFL

Just remember, standby mode disables anti-theft and communication with Mercedes Me like I mentioned earlier.

TonyG3D

Yes, I'm aware of that, but my place is very safe. I just like to be able to check and control things in case I have to, so a trickle charger is a better option in my situation.

bsaz

I have been using battery chargers for many years,on multiple vehicles, (they are pretty much connected most of the time when sitting in the garage). I probably drive each 2K+/year. Batteries here is AZ last 3-4 years (if lucky), even when garaged most of the time. I have a 2021 GLC 43 connected to Schumacher 600a-CA 6 amp. charger (OK with AGM batteries), goes into trickle after full charge, longest period without driving was two weeks, no issues. I have been using this regiment for the three years of ownership of the GLC.
(Just purchased a '24 BMW X5 M60i, talking about super complex battery management, with the 48V + the 12V system, bidirectional charge controller etc. Far cry from the old days!)
I

W205C43PFL

I thought I mentioned it because you specifically mentioned you wanted to be able to track the car and see the status of the car via Mercedes Me, so standby mode doesn't work for you in that case.

W205C43PFL

Thanks for sharing your experience.

TonyG3D

Yes, exactly. I like to be in control! 😉

W205C43PFL

Fair enough : )

superswiss

There's really not much if anything useful to control on the car while away, and other than the battery charge, the status won't change, either. The car is effectively in sleep mode. I admittedly have invested into smart home tech over the recent years and it's been a great piece of mind to have visibility into the home while I'm away and know that it is secure. As long as my garage and home are secure, I know that the car is secure. Should anybody force the garage door open, I'll get a notification on my phone and if they find the key to the car and steal it, it will come out of standby mode and I will be able to track it. That's in addition to the alarm system going off at my house and the police being called immediately.