I’ve recently removed the rear jump seats to build a platform for storage, power and water systems as I convert my 2005 LR3 into an overlanding beast. So far, everything’s working out perfectly, but now I’m to the tricky electric system that I’m adding. I have everything ready to go (renology dc2dc converter, 50Ah battery, etc) but I want to make sure I have a great ground. The chassis is completely exposed so I figured I could sand down the area around on of the original jump seat bolts and use it as a ground. Possible?

The exposed bolt hole under the black mount for the power deck is where I want to put the ground. It’s the original rear jump seat bolt location.

 

Yes, it is possible. BUT.......... What kind of current (amps) will you be pulling? Keep in mind that doing so makes the chassis the new ground wire and as such any electronic module between the charger and main battery may be effected. Where will your batteries for this system be located? will any of the devises that you will be powering connected to the chassis ground? Also, most everything else on the car is grounded to the chassis near it so......there is that. I have my fridge connected to both pos and neg to the aux battery, I run my ham radio grounded behind the left rear trim panel next to the bluetooth module and it draws 30 amps at full power, so far, no problems.

I have done it both ways with no issues so far.

I am no curious, tell me more about your "tricky electrical system"


Jeff

 

Thank you for jumping on this thread. I mainly said it's tricky because it's been a very long time since I did anything like this, and my setup is something I haven't done before (a far cry from the stereo systems I used to mess with in High School). Here is what I am doing:

I am setting up two independent systems; for clarity, we can call them the primary and the secondary. The primary system is just an auxiliary Auxbeam 8 gang switch hooked up to my engine battery and powers everything I need when the car is running: front led lights, internal fan, engine fan (extra), cabin USB, GMRS radio. This uses the engine battery positive (fused before it joins the Auxbeam with a 40A circuit breaker) and the ground right next to the secondary battery box in the engine compartment. It resides in the secondary compartment.

The secondary battery system is set up in the car's rear and shares nothing with the primary, except for a positive run from the primary battery to a Renogy DC2DC charger that uses a 40A circuit breaker between the connections. I also have a 110-watt hood-mounted solar panel that runs to the PV+ of the DC2DC charger; this uses a 30A circuit breaker between the connections. The positive and the negative from the DC2DC charger go to two 4-post bus bars (one positive and one negative). The positive bus car is then connected to a Renogy 50Ah Lithium battery and a second Auxbeam 8 gang switch that powers the fridge, lights, fans, electronic heater fan, exterior camp lights, USB plugs, a small water pump, etc. (this also has a circuit breaker, but at 30A). Everything is pretty low on the Amp front, the fridge pulls about 7.5 Amps (https://www.dometic.com/en-us/outdoo...8aArYpEALw_wcB), and that's probably the biggest appliance. The air compressor probably pulls a good amount of power, but it will be rarely used (it's a Viair 300P and says on it that its maximum is 30A).

The negative bus bar off the DC2DC charger will ground the Renogy 50A battery, the Auxbeam 8-gang switch box, and the compressor. This is the ground in question.

If it helps, I am running 6 gauge wire for all positive and negative connections, except for the main connection for both bus bars and the main ground; those are 4 gauge. Any help here would be appreciated. I am mocking it all up on the board that will hold it all and can share a picture if any more clarification is needed (it isn't assembled yet as I still have some questions).

 

You are fine, no issues. Like you said, expose some metal there first and I recommend an electrical contact enhancer grease which will help prevent oxidation/corrosion. I use stuff from the telephone cable industry. I myself removed the second row of seats and have a "supply" module that drops in. It has water tanks and electrical mains and connects via an Anderson plug. I used the lower driver seat belt strap bolt as my ground. Closer to the engine bay with my aux battery.

If you run anything off the starter, I recommend a primary master switch or automatic relay to cut power to those accessories since your setup does not have a smart solenoid for being able to jump yourself. You could accidentally drain your starting battery. I also assume your aux battery in back will be lithium or such so you won't get out gassing?

 

Your setup sounds amazing, got any pics? Thank you for the great tips; I think the ground would be better in the back rather than running a 15' 6 gauge common ground from the main engine/battery. I am not planning on running anything from the starter in the back, and every main run (power, solar, etc) has a circuit breaker that I can shut off when not in use. The primary Auxbeam switch setup has a relay, so it will only work when the car is on. The battery in the back is lithium - for now, just a 50Ah Renogy - I don't think I need more for what I am running, but I left some room to move to 100Ah.

On a side note - my main battery is a slick lithium ion Antigravity battery that can jump-start the car if needed.

As for the grease - do you mean something like this -

 

Di-electic is non-conductive, it is an insulator. It should never be put on contacts, just the areas around or on connector seals. This is what I bought. You use very little, if you can see it you prob put too much. Works good on battery terminals too.