Recently we have accidentally left our 300SE's doors open, i.e. the dome lights on, overnight (we are slowly adapting to our new life with our second boy ;-) ), and obviously had the unpleasant surprise of a dead battery the next day.

Which made me think that it would be very useful to have two things on a car:
* An automatism which would switch off the battery when the minimum reserve needed to start the car has been reached. I.e. an automatism similar to that existing on laptops.
* A voltmeter, which would let you know when you have sufficiently recharged the battery after jump starting and letting your engine run to refill it.

It seems that voltmeters were common on older cars. I wonder why they were apparently removed from newer ones.

I have however never heard of a laptop-like, automatic battery switch off automatism on vehicles, which would however be critical at times...

Any opinions, additional information, etc.?

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1991 W126 300SE (M103)
1995 W124 E320 Wagon (M104)

automatism???? what in the name of baby jesus is that ???? lol......

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1990 560 SEL- "Goldielocks"
1984 300SD TurboDiesel- "Ole' Blue"

Modern cars (as in, like after 1993ish) have had features like that forever. In fact, tonight I was working on my uncle's '96 chevy cavalier....and left the trunk open, after 10 mins the light shut off. Lowering and raising the trunk lid powers it back up. Same for the interior light.

Our caravan shuts off the lights after they've been left on for 15 mins.

On an older car, the solution is to remember to close your doors! Who forgets to close the door on their car? I can't even fathom that....

Also, the average MB battery is big and powerful enough to run the dome lights for like 2 days.....so overnight accidental shouldn't be an issue if you have the correct battery (and a healthy one) installed in the car. I've left my dome light on (switched on) in the car overnight before....it had no effect on the battery.

They've been selling a device that monitors current usage on the battery when the car is off for ages....its like "the battery saver" or something....if it detects an abnormal flow for a certain amount of time (like your lights left on) it cuts power. Then it resets when you start the car.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

There is an automatic shut down for boats and also made for cars. Check boaters world for the maker (I will find it if I have time). Battery power is run through it and it has a trigger wire that you would attach to a parking light or something else that is not on with the switch off. When the battery gets low it will disconnect and Waite for the key to be turned on and the hen the parking light turned on will trigger it back on. Porsche and BMW will drain their batteries just sitting for a week or so. You will loose all settings on radio and alarm.
Not worth the $79 or so in my opinion though.
Robert