12v outlet in boot - battery charging
Thread Starter
Super Member
Joined: Dec 2005
Posts: 785
Likes: 113
From: Scottsdale, Arizona
2020 S63 Coupe, 2006 Hummer H1 Alpha, 2018 McLaren 720S, 2022 Porsche 911 TurboS, 2022 Tesla Model X
12v outlet in boot - battery charging
I didn't get a trickle charger with my MY15, so I just bought a CTEK Lithium charger w/ 12v cig adapter, assuming it would charge via the power outlet in the boot. But seems in my car this is switched, so cannot be used for charging... I assumed that was its purpose 
Is this some quirk with my car or all they all like this ?
I cannot find any other battery in the car, just the one in the boot behind the vertical trim piece - A123 Systems, 78aH, LiFePo4. I can of course use the alligator clips on the jump start terminals under the hood, it is just inconvenient particularly since the ground is underneath a plastic cover.
Is this some quirk with my car or all they all like this ?
I cannot find any other battery in the car, just the one in the boot behind the vertical trim piece - A123 Systems, 78aH, LiFePo4. I can of course use the alligator clips on the jump start terminals under the hood, it is just inconvenient particularly since the ground is underneath a plastic cover.
Thread Starter
Super Member
Joined: Dec 2005
Posts: 785
Likes: 113
From: Scottsdale, Arizona
2020 S63 Coupe, 2006 Hummer H1 Alpha, 2018 McLaren 720S, 2022 Porsche 911 TurboS, 2022 Tesla Model X
It plugs right in using the 12v cig connector, but the outlet is not electrified when the car is turned off so it does not charge.
I've had to use the jump connectors in the hood to use the charger... which is what it says to do in the operator's manual, too.
I've had to use the jump connectors in the hood to use the charger... which is what it says to do in the operator's manual, too.
Last edited by Heisenberg; Dec 20, 2017 at 12:38 PM.
Junior Member
Joined: May 2021
Posts: 57
Likes: 7
F250
Can you just use any old charger on the points under the hood or does it need something special?
I had to store mine while doing some house renovations and it took longer than expected. Battery completely dead.
2015 and suspect I will have to change it but just need to get it moved for now.
Should I just jump it? Or give it a little charge?
I have a basic cheapie 12V allegator clamp charger I charge other batteries with and also a trickle charger for my motorcycle I can switch to LI type. Does it matter?
I had to store mine while doing some house renovations and it took longer than expected. Battery completely dead.
2015 and suspect I will have to change it but just need to get it moved for now.
Should I just jump it? Or give it a little charge?
I have a basic cheapie 12V allegator clamp charger I charge other batteries with and also a trickle charger for my motorcycle I can switch to LI type. Does it matter?
Junior Member
Joined: Jan 2021
Posts: 16
Likes: 1
From: Central Texas
2016 S63 AMG
Some models came with an outlet on the driver's side and a "factory" trickle charger (Convertibles?) My MY 2016 does not have an outlet on the driver's side. The passenger side outlet "times out" with the ignition off and is not suitable for charging the battery.
My MB dealer re-wired the trunk outlet on the passenger side directly to my battery. Works perfect and an easy solution.
By the way.... I just replaced the Lithium battery due to age (ten years) Dealer charged...over $2500. (including vent adapter) I would recommend only using a charger rated for lithium batteries.
Norm
My MB dealer re-wired the trunk outlet on the passenger side directly to my battery. Works perfect and an easy solution.
By the way.... I just replaced the Lithium battery due to age (ten years) Dealer charged...over $2500. (including vent adapter) I would recommend only using a charger rated for lithium batteries.
Norm
Last edited by Normg; Sep 15, 2025 at 08:27 AM.
Junior Member
Joined: May 2021
Posts: 57
Likes: 7
F250
Ok I just bought a charger off Amazon with the best reviews.
Yeah with my battery being 10 years old I bet its due. I will need to see if there is anything aftermarket available or just do it the easy way through MB dealer.
Yeah with my battery being 10 years old I bet its due. I will need to see if there is anything aftermarket available or just do it the easy way through MB dealer.
MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,153
Likes: 1,767
From: Colorado
G550
AFAIK, all the 12V receptacle are switched. Interestingly, when I was doing some maintenance on my Jeep Rubicon recently, I discovered that its cargo area 12V outlet is powered through a fuse that can be positioned in a switched or non-switched position -- a great idea ! Other car manufacturers should do this.
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MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,153
Likes: 1,767
From: Colorado
G550
Super Member
Joined: Oct 2015
Posts: 908
Likes: 133
From: Tampa, FL
'17 AMG S63 Convertible, '17 AMG C63S Edition 1 Coupe
Some models came with an outlet on the driver's side and a "factory" trickle charger (Convertibles?) My MY 2016 does not have an outlet on the driver's side. The passenger side outlet "times out" with the ignition off and is not suitable for charging the battery.
My MB dealer re-wired the trunk outlet on the passenger side directly to my battery. Works perfect and an easy solution.
My MB dealer re-wired the trunk outlet on the passenger side directly to my battery. Works perfect and an easy solution.
