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Does anyone know if leaving the hood and/or doors open prevents the vehicle from entering sleep mode?
I'm asking because I store the car with the hood and doors slightly open to allow for periodic battery charging, and to avoid "waking" the car up if I open a door.
So, my main question is: does the car consume more battery power if the hood and doors remain open for an extended period—will the car still enter sleep mode?
While awaiting responses, I took some measurements.
The measurements were taken with the car unlocked, the doors, trunk and hood open, and with a fully charged battery. The measurements were taken directly on the negative cable at the trunk's battery with a calibrated DC clamp meter--accuracy of ±2% +8 mA.
Immediately after unlocking the car and opening the trunk, the current draw was approx. 9 amps. After about 20 seconds the current dropped to approx. 3 amps and continued to steadily decline over the next 30 minutes, reaching approx. 20 mA.
After another 10 minutes, the current further decreased to below 10 mA which I assume is sleep mode. Once in sleep mode, there were random pulsations up to 20 mA which I'm assuming is car/key communication. These pulsations stopped once the car was double locked (key double tapped and all doors still open) and in sleep mode.
For anyone wondering whether it's okay to leave your hood, trunk or doors open to assist with battery charging or monitoring, it appears that, at least for the 2019 450, the vehicle will still enter sleep mode and draw only the minimal necessary battery power.
I hope some find this info useful.
Last edited by hornethandler; Dec 7, 2025 at 01:43 PM.
Good question. Good thread.
It points out how so many of these features, and system designs ar a mystery to owners.
I noticed in the showroom, all the ICE cars were hooked up to trickle chargers, with the hoods closed.
I think I could probably close my hood after I hook up the CTek, but I don’t want to.
Connecting the charger already requires opening the hood, because I don’t have a remote charging point.
I am not going to close the hood while charging, because that adds a whole “nother” close cycle.
I really don’t worry too much about the parasitic draw when I leave it like that because it’s charging faster than it’s discharging.
But it would be very nice to know if I could leave it like the OP Hornethandler does, and what if any consequences I am considering.
Curious, but why are you worried about waking the car?
I store the car for 6 months, but don’t leave a battery maintainer on 24/7.
Waking the car activates modules that draw current from the battery. According to the measurements I took, the modules initially draw about 3 amps which slowly drops to about 20 mA over 30 minutes, before they go back into sleep mode.
Leaving the hood, doors, and trunk open enables me to inspect the vehicle without activating the modules or draining the battery, thereby reducing the frequency of battery charging and preventing unnecessary cycling of the modules.
Last edited by hornethandler; Dec 7, 2025 at 08:26 PM.
I store the car for 6 months, but don’t leave a battery maintainer on 24/7.
Waking the car activates modules that draw current from the battery. According to the measurements I took, the modules initially draw about 3 amps which slowly drops to about 20 mA over 30 minutes, before they go back into sleep mode.
Leaving the hood, doors, and trunk open enables me to inspect the vehicle without activating the modules or draining the battery, thereby reducing the frequency of battery charging and preventing unnecessary cycling of the modules.
If you can't keep a battery maintainer on it 24/7 then probably the best option for long-term storage is to disconnect the battery by pulling the negative terminal cable. Mercedes recommends this if the car is left unused for 6 weeks or more. Newer cars don't lose their settings when the battery is disconnected.
If you can't keep a battery maintainer on it 24/7 then probably the best option for long-term storage is to disconnect the battery by pulling the negative terminal cable. Mercedes recommends this if the car is left unused for 6 weeks or more. Newer cars don't lose their settings when the battery is disconnected.
Loosing the settings, as well as requiring other maintenance action, e.g., recalibration, adaptations, coding etc. after disconnecting the battery is what I was worried about.
A couple of questions:
Will the soft close doors and trunk still open and close manually?
Should the ECO start-stop battery be disconnected as well?
Last edited by hornethandler; Dec 8, 2025 at 08:05 AM.
You should be able to force the car into sleep mode by double clicking the lock button on the FOB.
6 months is going to be a long stretch without a battery maintainer though.
I believe the car won’t go into sleep mode if doors are open. I’m traveling but, I can check XENTRY when I get back to my shop to see if that’s the case. You can look at the front SAM in XENTRY and it will show you electrical consumption while car was in sleep mode.
I can’t remember off the top of my head, but does the facelift r231 give you a warning if the hood is open? The pre-facelift cars don’t, so can go into sleep mode with hood open. The Aux battery is essentially disconnected when car is off.
Last edited by crconsulting; Dec 8, 2025 at 09:12 AM.
Loosing the settings, as well as requiring other maintenance action, e.g., recalibration, adaptations, coding etc. after disconnecting the battery is what I was worried about.
A couple of questions:
Will the soft close doors and trunk still open and close manually?
Should the ECO start-stop battery be disconnected as well?
I've had my 2014 SL battery disconnected for several days while working on it and had no issues.
Soft close will obviously not work, but you can open and close the doors without a problem.
But be careful with the trunk. When I disconnect the battery I leave the trunk open so I can get back to the battery. In theory the metal key can be used to open the trunk, but from lack of use that can seize up leaving you unable to get into the trunk. I usually put something over the trunk catch so it can't be closed accidentally.
The ECO start/stop battery is isolated from the system except when the computer closes a solid state relay during ECO restart or when it decides the battery needs charging while the engine is running. It should be fine as is.
I've swapped out both the main and aux batteries before. I've also had them both disconnected at the same time for more than 30 minutes. I think the only thing I ever had to do was recalibrate the side windows by lowering them and holding the button down for a few seconds and then raising them and holding the button up for a few seconds. I'm not sure, but I think if COMAND gets locked up, the dealer can unlock it for you. Some dealers may do it gratis and some may charge.
You should be able to force the car into sleep mode by double clicking the lock button on the FOB.
6 months is going to be a long stretch without a battery maintainer though.
I believe the car won’t go into sleep mode if doors are open. I’m traveling but, I can check XENTRY when I get back to my shop to see if that’s the case. You can look at the front SAM in XENTRY and it will show you electrical consumption while car was in sleep mode.
I can’t remember off the top of my head, but does the facelift r231 give you a warning if the hood is open? The pre-facelift cars don’t, so can go into sleep mode with hood open. The Aux battery is essentially disconnected when car is off.
Thanks for weighing in…
After reading your post, I rechecked the vehicle with all doors closed--except for the trunk since I needed to read the clamp meter on the battery negative cable--and double clicking the lock button. It did not immediately enter sleep mode when I double-clicked the lock button, so perhaps having the trunk open is preventing it from sleeping. The behavior (current draw and timing) was the same as my post above with the doors open and vehicle unlocked.
I usually top up the battery every couple of weeks and I’d probably still do that even if it was disconnected.
Additionally, I do receive a visual warning—an image of the vehicle with a red highlight indicating any open panel—when a door or panel is open.
Last edited by hornethandler; Dec 8, 2025 at 11:17 AM.
I've had my 2014 SL battery disconnected for several days while working on it and had no issues.
Soft close will obviously not work, but you can open and close the doors without a problem.
But be careful with the trunk. When I disconnect the battery I leave the trunk open so I can get back to the battery. In theory the metal key can be used to open the trunk, but from lack of use that can seize up leaving you unable to get into the trunk. I usually put something over the trunk catch so it can't be closed accidentally.
The ECO start/stop battery is isolated from the system except when the computer closes a solid state relay during ECO restart or when it decides the battery needs charging while the engine is running. It should be fine as is.
Still on the fence about disconnecting the battery. It's not a problem to charge the installed battery every couple of weeks; however, is it better to disconnect it?
That's great to know about the doors working without the soft close working. I've asked the question before, but the answers never seemed conclusive.
I knew from our previous battery discussions that the Aux. battery is pretty much out of circuit when the vehicle is off, but I wanted to again hear from the experts.
Yeah, I do the same with the trunk... a small piece of carboard on the catch to prevent it from closing.
Last edited by hornethandler; Dec 8, 2025 at 11:55 AM.
If you can't keep a battery maintainer on it 24/7 then probably the best option for long-term storage is to disconnect the battery by pulling the negative terminal cable. Mercedes recommends this if the car is left unused for 6 weeks or more. Newer cars don't lose their settings when the battery is disconnected.
It's not a problem to charge the installed battery every few weeks. I monitor it and charge it whenever it drops a couple hundred mV or so.
It's not a problem to charge the installed battery every few weeks. I monitor it and charge it whenever it drops a couple hundred mV or so.
Should I continue that or disconnect it?
If there's any chance you'll take it for a drive then I'd keep doing what you're doing. If it'll sit unused the entire winter then I would disconnect the battery.
I suggest using a battery maintainer rather than a charger to avoid overcharging the battery.
If there's any chance you'll take it for a drive then I'd keep doing what you're doing. If it'll sit unused the entire winter then I would disconnect the battery.
I suggest using a battery maintainer rather than a charger to avoid overcharging the battery.
Thanks for getting back.
I typically put the car on the road for a couple of days around month 3 of storage just to lube things up.
And, as you suggested, I'm using a CTEK "maintainer" not a charger.
@hornethandler do you also put the car on jack stands or equivalent? I imaging letting the car sit for months may cause flat spots on the tires.
That's a good idea, but I don't.
Instead, I inflate to about 45 psi and manually roll the car a few time during storage. So far I haven't had any flat spots.
That's a good idea, but I don't.
Instead, I inflate to about 45 psi and manually roll the car a few time during storage. So far I haven't had any flat spots.
Thanks for weighing in…
After reading your post, I rechecked the vehicle with all doors closed--except for the trunk since I needed to read the clamp meter on the battery negative cable--and double clicking the lock button. It did not immediately enter sleep mode when I double-clicked the lock button, so perhaps having the trunk open is preventing it from sleeping..
You can tell when/if the car goes into deep sleep as the doors won’t open by touch. You need to use the key fob to unlock the doors.
Originally Posted by hornethandler
The behavior (current draw and timing) was the same as my post above with the doors open and vehicle unlocked.
My guess is the trunk might be keeping the car from going into deep sleep. (Not sure it will go into that sleep mode with doors open.)
Originally Posted by hornethandler
Additionally, I do receive a visual warning—an image of the vehicle with a red highlight indicating any open panel—when a door or panel is open.
If you get that warning light with the hood open, it’s possible that would keep the car from going into deep sleep also. I think that’s a feature MB added with the facelift cars, if the hood triggers a light. I know many of the newer MB’s have this feature, so that makes sense.
I would think if you used a battery maintainer under the (shut) hood and put the car in deep sleep it would be good for 6 months.
There are pads you can buy to help with tire flat spotting,
You can tell when/if the car goes into deep sleep as the doors won’t open by touch. You need to use the key fob to unlock the doors.
Contrary to my other post, I guess my car never sleeps because the doors always unlock when I touch them (unless the fob is in the same pocket as my phone, which tends to block the signal).
I wonder what Tom Selleck would have done if the Ferrari had touch handles. It would have made the opening scene less dramatic. (Magnum PI reference.)
Contrary to my other post, I guess my car never sleeps because the doors always unlock when I touch them (unless the fob is in the same pocket as my phone, which tends to block the signal).
The car doesn’t enter that mode until you force it with by double clicking fob.
When I get back to my shop I’ll see if I can get a before and after deep sleep measurement from the front SAM with XENTRY to see how much of a difference it actually makes.
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