I seem to have had an increase over the last few weeks of emails from people involved in building, modifying or upgrading Overland Expedition type vehicles. I think some of my posts must have been quoted or referenced in related forums. A lot of questions are related to roughly the same group of topics so I thought I’d produce three drawings to help answer the bulk of the questions. If you read down the comments on some posts I have answered a lot of specifics that might help. I’ve merged a lot of the questions into a paraphrased ones…
Question 1
“How can I get my LED light bar and spotlights to come on when I use my main beam switch but I want to disable them when on the highway?”
Link to A3 PDF – Auto Switch Driving Lights
The questions were from a number of 4 x 4 Off Road enthusiasts and Overland vehicle people. Simplest way I could come up with was using a couple of diodes (details on the drawing) Three switches… one for LED Light Bar, One for Driving Lights and one that allows you to sync the LED Light Bar and Driving Lights to the operation of the main beam in the vehicle. Flash the main beam and with the Sink Switch ON… all the lights will flash. Note… this may be illegal in some countries, so having the option to turn off the facility when on the roads ‘should’ keep you within the law…. don’t quote me on it!!!
Question 2
“Whats the best layout for connecting a solar controller / inverter / isolation switch to my battery bank?”
Link to A3 PDF – Overlander Wiring Diagram – 01
The best schematic I could come up with that is flexible for most situations. I’ve put a few notes on the drawing. The various components I’ve drawn generically…. all can be found at your preferred supplier.
Question 3
“What’s the basic layout of the vehicle fridge and leisure battery charing circuit?
Link to A3 PDF – Basic 13 Pin Power Loom 1
This I think has come from a few on-line discussions relating to poor performance of the fridge and leisure battery charing in older 4 x 4 vehicles. I was receiving for a while a number of questions related to upgrading older installations. I also receive a number of emails asking how to add the facility of fridge and leisure battery charging to older vehicles and upgrade the 7 pin tow socket or old military lights socket.
You can download the PDF’s and are free to use for personal use. If you post them on other forums I’d appreciate a link back to this page and/or an acknowledgement.
I’d appreciate any feed back in the comments below.
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Nigel Chapman said:
Hi. I’m really hoping that you can help me.
I need advice on cable mm2.
A quick summary of my solar panel system. 450w panel, 60a mppt controller and a 40a dc to dc charger( I’m using 16mm2 cable)two 240ah agm 12v batteries that intern supply a 3000w/9000w inverter. Originally I intended to use 70mm2 cable to supply the inverter as both batteries would be within 0.5m of inverter. But due to space I now have to have one battery 2.5m meters away from the inverter. So now I’m totally out of my depth about selecting the correct mm2 cable to (A) connect the batteries together in parallel and the inverter. Any advice would be greatly appreciated.
Nigel
Simon Barlow said:
The rule is size the cable for the furthest battery… so do the volt drop calculation as thought BOTH batteries will be 2.5m from the inverter. That will give you the correct size and use that to cable both batteries to the inverter.
It’s better to be oversize not eh closer battery rather than undersize on the furthest battery.
Additionally, it will be easier ordaining terminals, heat shrink and you can probably reduce the amount of ‘spare’ cable you would need in two sizes over what you would need in one size.
Nigel Chapman said:
Thanks for the information. Now I can order the cable without worrying if I’ve got it wrong.
Regards
Nigel.
Nigel Chapman said:
Sorry to be a pain but, what is the best way to connect the batteries to the inverter. Normally I’d take a positive from one battery and the negative from the other.
Simon Barlow said:
Spot on…. if you draw it out on a bit of paper, you will see that you actually need three cables between the batteries….. pos and neg connecting them together, then an extra neg to feed your inverter. I alway opt for the the extra cable to be neg as it reduces the cable actually carrying pos to one between the two batteries.
I try to keep the pos cables as short as I can.
Nigel Chapman said:
Excellent advice. I would never have thought about having three cables. Now I can buy the correct size and not waste time and money on the incorrect cables.
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Rich said:
Thank you Simon
Great diagrams
Ian said:
Very interesting post as we seem to have a constant issue with our fridge working on 12v while travelling. There is an expensive solution, but not willing to fork out that sort of cash for the odd occasion that we will require the fridge working on 12v. When overlanding one of the last things you need to happen is for your battery to get fried. No spares shop around the corner. In the past I have got a lot of useful information from https://www.4x4community.co.za/forum/ as they have experienced many issues and have found ways to overcome these issues.
Richo said:
Ian
I find it better to run my fridge on 240v (Australia) via an inverter.
Christopher Swain said:
Hi reading this, I have had a good friend build me a clever unit that turns a small compressor fridge into camping fridge, it’s a 240v relay with snubbers, that allow a 300 watt inverter run fridge until plug into site then auto switches to mains and allows the charger to replenished the leisure batteries. We are going to also install a 80amp old style Lucas alternator directly to charging circuit to bypass all the can bus nonesence
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