Hi

I’m about to install an auxiliary battery on the flatbed and plan to ground it behind the rear lights. Do the chassis there provide enough connection to the front of the car or will I have to draw a negative cable all to the way to the battery?

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personally I would drill the x member under the tub mate and put a bolt through it make sure to use a washer both sides and sand back to bare metal

Quote: 123hotchef wrote in post #2

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personally I would drill the x member under the tub mate and put a bolt through it make sure to use a washer both sides and sand back to bare metal

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Quote: Linusp3 wrote in post #3

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Quote: 123hotchef wrote in post #2

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personally I would drill the x member under the tub mate and put a bolt through it make sure to use a washer both sides and sand back to bare metal

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Yes, I plan to sand the paint away and tap and use a bolt from the underside. The best location I found for this is here;


Why should I use a washer on both sides?
What do you mean by “x member under the tub”? Where is that?

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mine goes straight down to the chassis

through the grommet

Quote: 123hotchef wrote in post #4

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Quote: Linusp3 wrote in post #3

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Quote: 123hotchef wrote in post #2

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personally I would drill the x member under the tub mate and put a bolt through it make sure to use a washer both sides and sand back to bare metal

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Yes, I plan to sand the paint away and tap and use a bolt from the underside. The best location I found for this is here;


Why should I use a washer on both sides?
What do you mean by “x member under the tub”? Where is that?

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If it is for a battery idealy the earth needs to be to the chassix rather than body work. The X member that runs between the chassis, either the one that holds the spare of the one in front or behind it, or just the chassis rail itself where the tow bar bolts on

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can u get to the other side of that (chassis side?) what gauge cable are you using? the bigger surface area touching bare metal the better really as this will probably be the only source of ground for the 2nd battery

Quote: 123hotchef wrote in post #8

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can u get to the other side of that (chassis side?) what gauge cable are you using? the bigger surface area touching bare metal the better really as this will probably be the only source of ground for the 2nd battery

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no i mean the other side of the bit in the picture ie the inner side chassis side

10mm2 cable is only good for 70amps what battery are you fitting as the 2nd

i would be using 25mm2 at the minimum

40mm2 would be even better especially with the long run front to back and in the event you want to jump urself from 2nd battery

Using a thinner cable will be fine for the earth as it is extremely short if you are going to the chassis so 25mm will be more than enough for that. It all depends what you will be using it for. If you are going to be running the starter off it then you will need a separate wiring system to the charging system for battery jumping and a way to prevent current being drawn back through the charging relay during start up. The battery cables don't have to be crazy size wise. 25mm should be more than enough. Remember you are only jumping the start battery (in other words giving the main battery some extra juice) and the wiring doesn't have to handle a continuous 600A load, at the most it will be for maybe 5 seconds so spending a tonne more on extra copper will be a wasted venture.

Quote: Paddy1000111 wrote in post #12

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Using a thinner cable will be fine for the earth as it is extremely short if you are going to the chassis so 25mm will be more than enough for that. It all depends what you will be using it for. If you are going to be running the starter off it then you will need a separate wiring system to the charging system for battery jumping and a way to prevent current being drawn back through the charging relay during start up. The battery cables don't have to be crazy size wise. 25mm should be more than enough. Remember you are only jumping the start battery (in other words giving the main battery some extra juice) and the wiring doesn't have to handle a continuous 600A load, at the most it will be for maybe 5 seconds so spending a tonne more on extra copper will be a wasted venture.

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Quote: 123hotchef wrote in post #10

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no i mean the other side of the bit in the picture ie the inner side chassis side

10mm2 cable is only good for 70amps what battery are you fitting as the 2nd

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hard to tell from that picture but as long as it is clean to bare metal and the chassis it will be a perfect ground.

I would want to use 25mm2 cable with a 80ah battery as a minimum 10mm2 is very low rated for that long run

Quote: 123hotchef wrote in post #13

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why would one need a separate wiring system? I just used a relay and switch quick flick of the switch and I can jump myself no sperate wiring system needed just the switch.

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Quote: Paddy1000111 wrote in post #16

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For example 10mm2 wiring will deal with 30A continuous load at 12.6V (standard charged battery voltage) if the wire is 2 meters long. If the wire is 1 meter long however then 10mm2 wire can handle a continuous current load of 70A.

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Quote: Paddy1000111 wrote in post #16

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You need to add together all of the things you will be running and then work out how long the cable run will be. There's plenty of cable sizing tools online, this one is handy, just set it to 3% loss and use a voltage of 12.6V (The loading on the wire reduces as the voltage does up so you need to use the lower voltage) http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

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The earth on mine goes to the chassis , I drilled a hole for it , the kit I made myself from welding cable with a 200 amp relay and a manual switch on the dashboard to turn it on and off

Quote: Rob1307 wrote in post #18

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The earth on mine goes to the chassis , I drilled a hole for it , the kit I made myself from welding cable with a 200 amp relay and a manual switch on the dashboard to turn it on and off

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Earth point on the rear chassis

So when we’re talking ground, might someone know the colour scheme of the -08 L200 cables? I unhooked the 12V plug between the front seats without checking first... one cable is black, the other one blue with a red mark.

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the black with silver bands will go to ground easy to check urself with a multi meter on ohm setting

I have put mine under the bonnet.