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I recently noticed my battery is draining significantly. Albeit I don't drive too often however I did do a longer drive recently to recharge the battery (around 100miles). I get home, checked the volts 12.8v...Ok good that's a healthy battery and cold cranks are fine. The next day I would check again, it dropped to 12.62v. Which is almost at the border line (shouldn't be below 12.6v). Note that this is a brand new battery as well.
So I started checking for parasitic draws and I realize with everything off (I also waited like 10 mins after), I am still seeing a 6-8 amp draw initially. So I then just kept the probe on and waited to see if it settles down. Eventually it goes down to 1-3 amp draw. That is still way too high (should be below 50mA from what I heard) and can easily drain the battery down in just couple days of not driving. I am wondering is it because of these "modern" cars and its "smart" electronics, it does indeed always have juices flowing to power some of these modules or do I really have an issue with something.
Do you leave anything plugged in to the AirPlay USB port? That particular port seems to always be live. I have a wireless AirPlay adapter in my 2020, and looks like phone stays connected to it way after I lock the car. Now sure how much power it draws though and haven’t monitored it long enough to see if that port stays alive indefinitely, but could lead on to something.
*Edit.. Looks like USB port does go to sleep between ~25-30 minutes or so. My Airplay device has a blue light when ON which went dark after that period. It also dropped from my phone's available WiFi networks.
Last edited by Turbogate; Jul 31, 2023 at 11:03 AM.
Do you leave anything plugged in to the AirPlay USB port? That particular port seems to always be live. I have a wireless AirPlay adapter in my 2020, and looks like phone stays connected to it way after I lock the car. Now sure how much power it draws though and haven’t monitored it long enough to see if that port stays alive indefinitely, but could lead on to something.
Do you have anything plugged into the OBD port ... if you do, that'll likely be the culprit as such devices will often keep various modules alive responding to queries?
Do you have any dashcams installed (or any other after-market accessories)? Dashcams operating in parking mode will often draw 150-300 mA.
I'd expect it to take more than 10 min with the key out of range of the vehicle for things to completely settle down. After 20 min (with the key out of range), I'd be worried.
Do you have anything plugged into the OBD port ... if you do, that'll likely be the culprit as such devices will often keep various modules alive responding to queries?
Do you have any dashcams installed (or any other after-market accessories)? Dashcams operating in parking mode will often draw 150-300 mA.
I'd expect it to take more than 10 min with the key out of range of the vehicle for things to completely settle down. After 20 min (with the key out of range), I'd be worried.
Yeah nothing in OBD and I removed the dashcam when I tested this. As for the key, that shouldn't be an issue because I removed the negative battery terminal and still waited 10mins after that.
I guess what I am trying to find out is what is the "normal" amp draw when all doors are locked and the car has already gone to sleep. Even though I heard it should be less than 50mA but I am not so sure that means all cars or just older cars with less electronics.
Could be your key fob is to close to your vehicle
Keeping it active . This can cause the battery to drain.
Try locking the vehicle by hitting the key fob twice till you hear the horn beep twice.
This will disable the proximity sensor.
Could be your key fob is to close to your vehicle
Keeping it active . This can cause the battery to drain.
Try locking the vehicle by hitting the key fob twice till you hear the horn beep twice.
This will disable the proximity sensor.
Yup I did that already. I also put the key fob in a faraday cage just in case.
I am probably going to just pull the fuses out one by one to find the issue. This is my last resort of course as it is so time consuming to do with I think 3 or 4 fuse boxes in total...
I'm not sure what the normal draw is at rest for these cars, but I suspect it's more than 50 mA. These modern cars are like smartphones. They are always on and connected to the Internet, so they can respond to requests from the Mercedes me app. It'll never fully go to sleep, and if you have poor cell coverage where the car is parked then like smartphones the draw will be higher, because it either keeps looking for a cellular network or needs to boost the signal to reach the nearest tower.
The FL addresses this with the standby mode, which allows for everything to be shut down. Also disables the alarm. It's meant for long term storage and with a full battery I get 21 weeks. The neat thing is that it displays how long you can leave the car parked before the battery needs to be charged. Even so, I don't drive much, either. Mostly only on weekends. The other nice thing about the FL is that it sends an alert to my phone if the battery charge is critical. It happens sometimes when the car is getting serviced and I forgot to fully charge the battery beforehand. It gets low after about two days if they are working on the car, but otherwise I never have battery issues and I leave the car unlocked in my garage. Key fobs are upstairs, though, and they automatically go to sleep after not sensing motion for 2 minutes. That's another improvement in the FL models.
Your draw might be normal, unless you find having to jump start it after only a few days.
Last edited by superswiss; Jul 30, 2023 at 06:41 PM.
I'm not sure what the normal draw is at rest for these cars, but I suspect it's more than 50 mA. These modern cars are like smartphones. They are always on and connected to the Internet, so they can respond to requests from the Mercedes me app. It'll never fully go to sleep, and if you have poor cell coverage where the car is parked then like smartphones the draw will be higher, because it either keeps looking for a cellular network or needs to boost the signal to reach the nearest tower.
The FL addresses this with the standby mode, which allows for everything to be shut down. Also disables the alarm. It's meant for long term storage and with a full battery I get 21 weeks. The neat thing is that it displays how long you can leave the car parked before the battery needs to be charged. Even so, I don't drive much, either. Mostly only on weekends. The other nice thing about the FL is that it sends an alert to my phone if the battery charge is critical. It happens sometimes when the car is getting serviced and I forgot to fully charge the battery beforehand. It gets low after about two days if they are working on the car, but otherwise I never have battery issues and I leave the car unlocked in my garage. Key fobs are upstairs, though, and they automatically go to sleep after not sensing motion for 2 minutes. That's another improvement in the FL models.
Your draw might be normal, unless you find having to jump start it after only a few days.
Could be your key fob is to close to your vehicle
Keeping it active . This can cause the battery to drain.
Try locking the vehicle by hitting the key fob twice till you hear the horn beep twice.
This will disable the proximity sensor.
Quick question. Is that something that has to be done every time you lock the car (to disable the proximity sensor)? or do you do it once and it remembers the setting next time you lock it? Thx
Quick question. Is that something that has to be done every time you lock the car (to disable the proximity sensor)? or do you do it once and it remembers the setting next time you lock it? Thx
Every time you exit your vehicle. (Every shutdown)
Must be done to disable proximity sensor.
Also the best way to stop thieves from scanning your key fob from outside with a Antenna amplifier.
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Anyone with battery parasitic draws?
