Installing a auxilery (backup) battery, work around solution for battery drain.
Thread Starter
Newbie
Joined: Dec 2013
Posts: 9
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From: Northwest UK
E320 CDi (2007 - S211), S500L (2002_W220), SLK280 (2007 R171)
Installing a auxilery (backup) battery, work around solution for battery drain.
Hi,
I have been plagued with the dreaded battery drain issue for some time now and have had to resort to removing the neg connection to the battery every time i stop.
I've traced many problems causing the canbus to stay alive (drivers door keyles lock button, GPS ant water damage, interior light door switch closed circuit, alarm backup batt amongst just a few of the things I need to sort).
I plan to take the car off the road at some point and work through these but I cant afford to be without it for now.
I have an idea to install a secondary small battery with an isolator switch that in the event I return to the car and the battery is flat I can switch it in and start the car without any drama (similar to the setup the Bentley C GT has).
I'm wondering if anyone has done this before and if so was it successful?
My plan is to install a small battery with enough power to start the car and connect it directly to the main battery in the boot via a 180Amp isolator (the type used on boats and race cars etc) and possibly wiring a large current capacity diode across the isolator switch to provide charging when the car is running and the switch is open?
any thoughts much appreciated.
Mark
I have been plagued with the dreaded battery drain issue for some time now and have had to resort to removing the neg connection to the battery every time i stop.
I've traced many problems causing the canbus to stay alive (drivers door keyles lock button, GPS ant water damage, interior light door switch closed circuit, alarm backup batt amongst just a few of the things I need to sort).
I plan to take the car off the road at some point and work through these but I cant afford to be without it for now.
I have an idea to install a secondary small battery with an isolator switch that in the event I return to the car and the battery is flat I can switch it in and start the car without any drama (similar to the setup the Bentley C GT has).
I'm wondering if anyone has done this before and if so was it successful?
My plan is to install a small battery with enough power to start the car and connect it directly to the main battery in the boot via a 180Amp isolator (the type used on boats and race cars etc) and possibly wiring a large current capacity diode across the isolator switch to provide charging when the car is running and the switch is open?
any thoughts much appreciated.
Mark
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Joined: Dec 2012
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From: Ball Ground, GA (N of Atlanta)
2003 S500 2007 GL450
That would work, but there might be a better way...
For about the same money, you can buy one of the small jump-start boxes that charges off the mains. Keep it in the trunk, and use it as necessary. The box will also be very useful for starting other vehicles, riding lawn mowers (I assume much less common in the UK than here), etc.
For about the same money, you can buy one of the small jump-start boxes that charges off the mains. Keep it in the trunk, and use it as necessary. The box will also be very useful for starting other vehicles, riding lawn mowers (I assume much less common in the UK than here), etc.
Thread Starter
Newbie
Joined: Dec 2013
Posts: 9
Likes: 0
From: Northwest UK
E320 CDi (2007 - S211), S500L (2002_W220), SLK280 (2007 R171)
I had the same idea Wally, I have a mini Li-Ion easystart i'm currently using but having to connect the crock clips every time is a bit of a pain, i was thinking of permanently installing a lead with an EC5 plug so I can connect it to the easystart prob via a isolator or 150a breaker.
My concern was that the frequent use may kill it in a short space of time.
Just liked the way Bentley did it though, maybe even wire in a starter solenoid that I can remote activate from the drivers seat to connect the jump start battery...
Even when all the faults are sorted out it would be useful to have a backup as even before the drain problem started if I parked the car up at the airport for a couple of weeks it was always nerve racking to return to the car and find out if it started or not.
My concern was that the frequent use may kill it in a short space of time.
Just liked the way Bentley did it though, maybe even wire in a starter solenoid that I can remote activate from the drivers seat to connect the jump start battery...
Even when all the faults are sorted out it would be useful to have a backup as even before the drain problem started if I parked the car up at the airport for a couple of weeks it was always nerve racking to return to the car and find out if it started or not.
Last edited by techcareuk; Feb 17, 2016 at 09:09 AM.
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Joined: Jun 2011
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From: Cape town
not a merc
Just wire up the secondary battery positive to positive but the second battery you fit the cut out switch to ground (either mechanical or with your remote setup.)
As soon as the ign is switched on you bring the second battery into the circuit. That way the second battery is always being charged while the car runs. Once you switch the car off the second battery will disconnect.
As soon as the ign is switched on you bring the second battery into the circuit. That way the second battery is always being charged while the car runs. Once you switch the car off the second battery will disconnect.
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Joined: Jan 2008
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Mercedes
As I said at benzworld
Get a battery brain t3 from Amazon
https://www.amazon.com/gp/aw/d/B000P...ttery+brain+t3
It's a remote controlled battery disconnect switch
Get out of the car , click the remote and the battery disconnects , preventing drain
Get back in the car , click the remote and the battery reconnects . No need to ever touch the battery or cables again
You will see most of the reviews of this product are from people looking to solve their battery drain issues
Get a battery brain t3 from Amazon
https://www.amazon.com/gp/aw/d/B000P...ttery+brain+t3
It's a remote controlled battery disconnect switch
Get out of the car , click the remote and the battery disconnects , preventing drain
Get back in the car , click the remote and the battery reconnects . No need to ever touch the battery or cables again
You will see most of the reviews of this product are from people looking to solve their battery drain issues
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Member
Joined: Jan 2015
Posts: 104
Likes: 27
From: Detroit, MI
2006 CLS55AMG & 2005 S55AMG
I have a couple ideas for you.
My 2005 S55 AMG had a battery drain. At first I would pull the neg cable off every night. Then I bought a battery disconnect switch from harbor freight for $10. That was better. Then I traced down the circuit in the can bus that was keeping the car "awake", and I would unplug that. I ended up installing a relay {under the diver side floor} that would open the can bus circuit that was keeping the car awake. I used a normally open, double pole double throw, relay that broke each wire {2 of them} feeding into the can bus, {the command unit circuit, in my car}. I wired the coil of the relay to power up whenever the key was on. That solved my battery drain.
You could also do the same thing, with a relay, to kill the power that feeds the central gateway under the dash, or unplug the central gateway over night. It is under the drivers side kick panel to the far right. I think, if I was you, I would kill the power to the central gateway with a relay. That central gateway is the "master" to the can bus. Kill the central gateway power supply and it can not keep the car awake when you shut off the key. The lower plug in the central gateway is the power supply. Use a relay SPST to open the ground {brown wire}. I have not actually tried killing the gateway to stop the battery drain, but I'm pretty sure it would work. The canbus circuits feed into the gateway. Disconnect the lower, two wire plug on the gateway overnight. If the battery did not drain, then my "fix" , a relay cutting power to the gateway, will work. I'm almost positive it will work. I know this because I forgot to reconnect my gateway one night and the battery did not drain.
My 2005 S55 AMG had a battery drain. At first I would pull the neg cable off every night. Then I bought a battery disconnect switch from harbor freight for $10. That was better. Then I traced down the circuit in the can bus that was keeping the car "awake", and I would unplug that. I ended up installing a relay {under the diver side floor} that would open the can bus circuit that was keeping the car awake. I used a normally open, double pole double throw, relay that broke each wire {2 of them} feeding into the can bus, {the command unit circuit, in my car}. I wired the coil of the relay to power up whenever the key was on. That solved my battery drain.
You could also do the same thing, with a relay, to kill the power that feeds the central gateway under the dash, or unplug the central gateway over night. It is under the drivers side kick panel to the far right. I think, if I was you, I would kill the power to the central gateway with a relay. That central gateway is the "master" to the can bus. Kill the central gateway power supply and it can not keep the car awake when you shut off the key. The lower plug in the central gateway is the power supply. Use a relay SPST to open the ground {brown wire}. I have not actually tried killing the gateway to stop the battery drain, but I'm pretty sure it would work. The canbus circuits feed into the gateway. Disconnect the lower, two wire plug on the gateway overnight. If the battery did not drain, then my "fix" , a relay cutting power to the gateway, will work. I'm almost positive it will work. I know this because I forgot to reconnect my gateway one night and the battery did not drain.
Last edited by hvacdude; Feb 23, 2016 at 09:27 PM.
Junior Member
Joined: Feb 2016
Posts: 34
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From: Mississippi
S500 w220
[QUOTE=Russell Ormerod;6710695]Just wire up the secondary battery positive to positive but the second battery you fit the cut out switch to ground (either mechanical or with your remote setup.)
As soon as the ign is switched on you bring the second battery into the circuit. That way the second battery is always being charged while the car runs. Once you switch the car off the second battery will disconnect.[/QUOTE
Can you be real specific and explain to me how to properly connect another battery to the stock one? Is it just negative to negotiate and positive to positive? Can I just wire it directly to the leads on the stock battery?
As soon as the ign is switched on you bring the second battery into the circuit. That way the second battery is always being charged while the car runs. Once you switch the car off the second battery will disconnect.[/QUOTE
Can you be real specific and explain to me how to properly connect another battery to the stock one? Is it just negative to negotiate and positive to positive? Can I just wire it directly to the leads on the stock battery?
Member
Joined: Jan 2015
Posts: 104
Likes: 27
From: Detroit, MI
2006 CLS55AMG & 2005 S55AMG
Why bother with a second battery that you use a disconnect switch on, when you can just put a disconnect switch on the main battery's negative side. You can get the switch for $6. Where are you going to put the second battery ? flopping around in the trunk, spilling acid that will destroy any thing it comes in contact with. http://www.harborfreight.com/battery...tch-97853.html
Junior Member
Joined: Feb 2016
Posts: 34
Likes: 0
From: Mississippi
S500 w220
Why bother with a second battery that you use a disconnect switch on, when you can just put a disconnect switch on the main battery's negative side. You can get the switch for $6. Where are you going to put the second battery ? flopping around in the trunk, spilling acid that will destroy any thing it comes in contact with. http://www.harborfreight.com/battery...tch-97853.html
Member
Joined: Jan 2015
Posts: 104
Likes: 27
From: Detroit, MI
2006 CLS55AMG & 2005 S55AMG
There is no room for a second battery. The battery fits tight in a hole for it. there is no room under the carpet cover, the spare takes up the whole underside of the trunk. There's no where to attach any kinda mount. You would have to use a bungee cord. It would look like crap and if something in the trunk shorts it out, God knows what damage the electrics suffer. You have to vent the battery also, or acid will ruin your trunk carpet. If you want a low tech, simple, cheap fix: get the disconnect I posted. I have one in my car and it works great, no splicing wires, takes 5 min to install and doesn't get in the way of anything.
Just turn it off when you park the car overnight if your not going to fix it right.
Just turn it off when you park the car overnight if your not going to fix it right.
Junior Member
Joined: Feb 2016
Posts: 34
Likes: 0
From: Mississippi
S500 w220
I'm going to mount mine right on top of the other one. My trunk is already full of gear and and lock mounts for long guns.
My issue isn't the same as the orginal poster, but the solutions would be the same. I need power for extended hours without the car running.
My issue isn't the same as the orginal poster, but the solutions would be the same. I need power for extended hours without the car running.
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Joined: Jan 2008
Posts: 6,150
Likes: 533
Mercedes
[QUOTE=michael neyman;6717556]
You want what's called a battery isolator
These are used on rv and other cars to power electronic when the car is off using the auxiliary battery
Then it charges them when the car is on
Just wire up the secondary battery positive to positive but the second battery you fit the cut out switch to ground (either mechanical or with your remote setup.)
As soon as the ign is switched on you bring the second battery into the circuit. That way the second battery is always being charged while the car runs. Once you switch the car off the second battery will disconnect.[/QUOTE
Can you be real specific and explain to me how to properly connect another battery to the stock one? Is it just negative to negotiate and positive to positive? Can I just wire it directly to the leads on the stock battery?
As soon as the ign is switched on you bring the second battery into the circuit. That way the second battery is always being charged while the car runs. Once you switch the car off the second battery will disconnect.[/QUOTE
Can you be real specific and explain to me how to properly connect another battery to the stock one? Is it just negative to negotiate and positive to positive? Can I just wire it directly to the leads on the stock battery?
These are used on rv and other cars to power electronic when the car is off using the auxiliary battery
Then it charges them when the car is on
Junior Member
Joined: Feb 2016
Posts: 34
Likes: 0
From: Mississippi
S500 w220
[QUOTE=tusabes;6717621]Thanks! That's exactly what I need. However I see a huge variety and prices. Do you have an idea of what would work best in an automobile? I hate to keep asking but electronics are my weak spot and I've never even heard of one before this. What's the difference between the 200$ ones and a 50$ from oriellys?
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