Our 4WD Dual Battery 12V Electrical Setup
4WD Electrical 12V Setup
In this post we take you through our dual battery 12V electrical setup in our 4WD, 76 (70) Series Toyota Land Cruiser. This post covers the setup and wiring for the dual battery, DCDC battery charger, pure sine wave inverter, 240V power board, on board compressor, 12V electrical outputs, switches, fuse box, anderson plugs, additional lighting and more.
For most of the wiring, especially the initial stages, we had assistance from Speedy Towbars on the North Side of Brisbane. Speedy Towbars specialises in towbars and wiring related to towing; however, they have the materials and expertise when it comes to this stuff as well as us having a great relationship with the business. As a result, we used them for assistance in obtaining the gear and commencing the more tedious work with the wiring.
Keep Your 4WD 12V Setup Simple
As anyone who does a lot of camping, touring, overlanding, and exploring knows, a good 12V electrical setup in your 4WD is a must. This does not mean you need to spend an insane amount of money on top of the range battery management systems with big LED displays and Bluetooth connectivity. What we mean here, is all you need is a good setup using decent gear having everything you need. Do not go cheap on key items but save money on others.
When it comes to 12V electrical setups in your 4WD, our opinion is to keep it as simple as possible so that you know how it all works if something goes wrong. The fancier and more complicated your wiring becomes, the more difficult it will be to solve any potential problems on your own. Remember, all those insanely fancy 12V electrical setups you see in 4WD influencer posts on social media are usually sponsored or heavily discounted, so doing the same in your setup is going to cost a bomb and let us face it, do you really need such a setup? Maybe you do…
Our advice here is to keep it simple and install all you really need. Do not over complicate things with expensive switches and hard to get to wiring. If you are not doing the wiring yourself, make sure you know how the wiring has been installed, where everything is going and how it is all connected. Do not use the cheapest gear but you also do not need to use the most expensive either. We did decide to go with a Redcar DCDC charger and inverter which are expensive. Firstly, we did not pay full retail, and secondly, we wanted our main components to be quality gear that have been tried and tested in Australian conditions. If we did not get the discount we received, we would have still chosen a Redarc DCDC charger however we would have found a cheaper inverter.
The Gear in Our Electrical Setup
Here is a list of the gear we have used and connected to our second battery in our 4WD 12V electrical setup:
- Redarc DCDC 40 Amp in-vehicle battery charger.
- Redarc 1000W pure sine wave inverter.
- Adventure Kings 115AH deep cycle AGM battery.
- ARB twin on board compressor.
- Waeco CFX50 fridge.
- Oricom UHF.
- 4 x 12V outputs – for lights in the awning and the rear of the Cruiser and a couple of spares to use for other accessories when needed.
- 3 x double USB outputs – to charge devices including phones, tablets, Bluetooth speakers, GoPro’s, and anything else that uses a USB to charge.
- CTEK CTX Battery Sense battery monitoring device for your phone.
- 7 x Adventure Kings LED camping light bars and switches in awning and rear of 4WD.
- 1 x voltmeter.
- 1 x power board for additional 240V sockets.
- 1 x internal grey anderson plug for the fridge.
- 1 x external grey anderson plug to charge trailer battery.
- 1 x external green anderson plug for solar input to charge second battery.
- 240V Thunder battery charger for 240V charge when needed for deep cycle AGM battery.
- 2 x fuse boxes connected to allow for a total of 12 fuses.
- Earth block plus a second earth terminal for larger wiring.
- Isolator switch to turn off all power from second battery and allow easy removal.
- 4 x anderson plugs connected to draws to allow easy removal without having to disconnect all the electrical components if ever needed – red for power from main battery, green for solar input, one grey to trailer, and one other grey for the earth.
All the above gear is connected in some way to the second battery in our 4WD. We are running other gear such as our LED spotlights, LED rear work lights, Runva winch and our Redarc Tow-Pro Elite V3 brake controller but these are all connected to our starter battery. Where possible we have tried to run everything that we can off our second battery to ensure that there is as little draw as possible on our starter battery.
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From the list above you can see that we have added and connected a lot of gear to our second battery. There is a bit of gear here, but we have tried to keep it as simple as possible when it comes to the wiring. There are no fancy switches, and all the wiring is easily accessible.
AGM vs Lithium Battery Setup
We decided at the start of the build that we would add a lithium battery to our 4WD 12V electrical setup. However, this was going to be added at a later stage due to cost. Initially we decided to add a cheaper deep cycle AGM battery and chose to use an Adventure Kings one. There is nothing wrong with this battery if you are looking at one of these but we only every purchased one as it was cheap and for the short term. We have since sourced a lithium battery off a supplier at a ridiculously good price so will be adding this in 2021.
We knew we would eventually install a lithium battery because of their weight, how quickly they charge and how they can pretty much go flat without causing any issues. The lithium battery we will be getting will be a 125AH and will weigh almost 20 kgs less than our current deep cycle battery; that weight saving is huge. Another great option with the lithium is we would basically need another two of our current deep cycle batteries to get the same performance as one lithium. But the biggest issue anyone is going to face here is the cost. Obviously, lithium batteries are far superior, but they come with a hefty price tag when buying a decent quality battery. With all that been said, we have not had any issues with our AGM battery, and we used the same brand and size in our previous 4WD without any issues as well. If you have the payload, GVM and space, then you will not have any issues using an AGM battery(s).
In summary, we currently run a 115AH deep cycle AGM battery that cost $250 but weighs around 30 kgs. We will be replacing this with a larger lightweight lithium battery shortly. As a result, we ensured when we fitted a DCDC charger that it was lithium compatible for this upgrade later. Just be aware of this, as there are some DCDC chargers that are not lithium compatible if you are ever thinking of upgrading. Look for LifePO4 if you are wanting a lithium compatible DCDC battery charger.
Redarc DCDC In-Vehicle Charger
We decided to go with a Redarc DCDC in-vehicle charger in our 4WD 12V electrical setup. There are many other options out there that are just as good, but we chose Redarc as they have a great brand, and their products are well tested in Aussie conditions. We have also used Redarc DCDC chargers in our previous 4WDs without having any issues so there was no point in changing. We would highly recommend using an in-vehicle battery charger as it does offer far more flexibility in a dual battery setup. Using your vehicles alternator to charge a second battery is not the best option. A DCDC in-vehicle charger ensures your second battery is receiving the correct voltage and current meaning the second battery charges correctly as well as prolonging its life. DCDC in-vehicle chargers that are solar compatible allow you to connect a solar panel as they have an inbuilt solar regulator.
DCDC in-vehicle chargers are compatible for different types of batteries. Make sure you are selecting the correct charger for your battery type. As we mentioned earlier, we chose a DCDC charger that was compatible for all battery types including lithium as we will be upgrading to one this year. When it comes to size, you need to ensure you are selecting the correct size charger for the number of amps required. Anything up to 25 Amps should be sufficient for batteries up to 200AH. Anything larger than 200AH will require a bigger charger. Our Redarc DCDC in-vehicle charger is 40 Amps which is currently bigger than what we need with a 115AH battery, soon to increase to a 125AH battery. Initially we thought we would be adding two batteries but that has since changed. As a result, we should probably go down to a smaller one like a 25 Amp charger but have not done anything about this yet. We are running the risk of degrading our battery life, but we will deal with this at a later stage.
Our Redarc DCDC in-vehicle charger is mounted behind our fridge to our rear drawer setup beside our second battery. We have solar input connected with a green anderson plug located beside our towbar if we ever want to charge our second battery via solar. We would highly recommend doing something similar if you ever plan to charge your second battery on solar. Our reasoning here is that it is a hassle having to run a cable through an open window or door to connect it to your charger. It is far easier connecting a cable to a connection on the outside of your 4WD.
To read more about our Redarc DCDC in-vehicle charger, check out our post here.
Redarc 1000W Pure Sine Wave Inverter
An inverter is only ever required if you are going to need 240V power. If you will not need 240V then this is a waste of money. However, from our experience having 240V power does provide you with a lot of options when travelling for any period. Our inverter allows us to charge laptops, camera batteries, lithium batteries for cordless power tools and even our electric toothbrush. We have seen others using their inverters to power portable ovens, electric blankets, and coffee machines. With inverters you just need to make sure that you work out what you will be connecting to it ensuring you have enough Watts to power it. For example, a coffee pod machine will need somewhere between 1,500 to 2,000 Watts. The bigger the inverter the more expensive it will be so bear that in mind when doing your calculations.
We chose a 1,000 Watt inverter as this was more than sufficient for what we need to charge. Inverters are bulky and need a bit of airflow as they can get hot. We chose to install ours on the side of drawers below a small shelf. Here the inverter is well out of the way over everything but has enough space to receive plenty of air. To make life easier turning the inverter on and off, we also purchased the Redarc remote switch. There is nothing complicated about this switch setup. You basically have a cable from the switch that connects to the rear of the inverter as well as a power cable. On the inverter you turn the power switch to the remote and this allows you to turn the inverter on and off. This is a great option if you are installing your inverter somewhere where it is not easy to access to turn on and off. We have fitted this switch at the front of our drawers for easy access. As the inverter comes with one plug outlet on the unit, we purchased a heavy-duty power board from VFM Group that we connected to the inverter and mounted in an easy to access spot on our drawers. This provides us far easier access to multiple 240V power outlets; this is probably overkill and we would have been fine with two outlets, but the power board is a good fit for our drawer setup and looks good.
Isolator Switch
An isolator switch to your second battery is highly recommended. There are many ways of doing this, but we kept it simple. We basically fitted an isolator switch that has a removable key, exactly what you usually get with any winch setup. The isolator switch has a positive negative terminal behind it. Here you to connect all your positives and negatives as well as the connections to the battery on this switch. This then allows you to turn off everything connected to your second battery by simply turning the isolator switch off. You will probably only ever use this when you are removing your battery for some reason, adding additional wiring to the battery or just need to turn everything off. This is not necessary, but you can pick up a good heavy-duty isolator switch for under $50 so we would recommend just adding on just in case.
Fuse Box and Earth Block
With any 12V electrical setup for your 4WD you will need a fuse box and some sort of earthing terminal or earth block. The fuse box will have a positive wire that is connected to your second battery. All your other positive wiring can then be connected to the fuse box and allow you to add the correct fuse. Here we used two small fuse boxes that connect to each other giving us a total of 12 terminals to use. Our fuse box also has a small red LED light that will light up if something is connected but the fuse is blown or disconnected. This is great as it does show you straight away where there is an issue if one exists. There are many options out there so just chose the right one for your setup based on size and features.
An earth block is like a fuse box without fuses. It allows you to connect one main earth and then all your other earths to this block. You can purchase an earth block, or you can make your own. We have one earth block as well as a separate earth terminal. The earth block is near the fuse box and has all the earths connected for all our small wires. We have then made an earth terminal, which is simply an M8 bolt, that connects the negative from the battery, the earth to the vehicle body and the earth cables that are larger and cannot access the earth block. In hindsight we could have done this part a lot better, but it all works and is simple enough to get to.
12V Outputs
Of course, when it comes to a 12V electrical setup in your 4WD you are going to need a few 12V outputs. Here we went a bit overboard mainly because we made a few additions to our drawers later and added a few more outputs in other spots. Currently we have four 12V cigarette socket outputs and another three 12V double USB ports. Three of the cigarette socket outputs and two of the double USBs are fitted to the rear infills of our drawers. There is another cigarette socket and double USD fitted to our rear drawer shelf. One of the cigarette socket outputs is permanently used for all our lights in the rear and awning. We have more than we need here and will moving some around for better access. We also added one voltmeter so that we can see the battery’s charge.
Battery Monitoring
Rather than waste our money on a super expensive battery management system, we instead chose to add a CTEK CTX Battery Sense smart battery monitoring device to our second battery. These are cheap and cost around $50. It is a small device that has a positive and negative cable with an inline fuse. You connect this to your battery and then download the CTEK Battery Sense application onto your phone. This then allows you to connect to the device via Bluetooth and then in a minute or so you can setup up your battery. The CTEK Battery Sense device allows you to connect to your battery and check the battery state of charge, voltage, and temperature. There is no other fancy information but all the information you need. With each reading you do get historical data on a line graph allowing you to zoom in or out to get any data you might want or need. For us this is more than enough information on our battery and do not really see the point in a ridiculously expensive battery management system. We are quite happy turning a switch to turn our lights on and off and do not need an app for that. Well, until we got sponsored one and our opinion will change 😊!
To read more about our CTEK CTX Battery Sense battery monitoring device, check out our post here.
Anderson Plugs
We have used many anderson plugs in our 12V electrical setup in our 4WD. As most of our wiring and gear are connected to our rear drawers, to allow us to remove the drawers easily, we used anderson plugs to connect any wiring that goes to the main battery and or anywhere else in the 4WD away from the drawers. This allows us to simply disconnect four anderson plugs and the drawers can be removed without having to mess around disconnecting lots of gear. We would highly recommend doing something similar if your setup is anything like ours.
We have also used Anderson plugs for our Waeco CFX50 fridge setup. Here we removed the cigarette type socket from the fridge power cable and replaced with an anderson plug. We connected another anderson plug to our fuse box, as this now need a fuse with removing the factory socket and mounted this plug near the rear of the fridge. Replacing your fridge connections with anderson plugs is a must as cigarette type sockets are hopeless and will come loose when driving bumpy and rough roads. Make sure you do this simple little upgrade; you will not ever have to worry about your fridge again.
Additional Lighting
You can see from our photos that the additional lighting we have added to our 4WD has worked an absolute treat. Here we kept this is super simple, well sort of. We did not waste money on expensive LED lights, but instead bought the Adventure Kings LED camping light bar kits. These lights are amazing and cost next to nothing. We have used these lights for years as well as in other 4WDs and have never had an issue with them. They do come with bulky twist connections to connect lights to cables and switches. So, where we did not want these, we simply removed them and soldered the wires together. The connections are good though for the lights in our awning. We have fitted four of these lights inside the rear of our 4WD as well as using the supplied dimmer switches to turn them on and off.
One light sits above the rear seats and shines forward to light up the front of our 4WD, this is on its own switch. The other three lights are mounted in different spots in the rear to provide plenty of lighting on the one switch. We have also fitted three lights inside our 270-degree awning. Here we used double sided tape and connected each light to one another using the twist locks that come with them. Inside the rear of our 4WD we have a two-metre cable that is rolled up and hidden away that is simply connected to the awning lights when we need to use them. The awning lights are also on their own dimmer switch. All up the lights cost us around $50-60.
Waeco CFX50 Fridge
We have had our Waeco CFX50 12V fridge for well over 6 years now, probably more. This is an awesome fridge that has never missed a beat. It has amble storage space and can be used as either a fridge or a freezer. The removable basked is fantastic as it allows you to pack your fridge in the house and then load it into your 4WD. The same can be said for unpacking when you arrive back home. The little shelf is not so little and gives you plenty more storage for those things that do not need to stay as cold. As we mentioned earlier, we removed the standard power outlet connection and replaced it with an anderson plug. Make sure you do this to your fridge as it ensures it never disconnects. But remember that the anderson plug you connect to must have an inline fuse to whatever your fridge manufacturer specifies. This is because the cigarette type sockets have an inbuilt fuse, so you need to replicate this if you remove this connection.
ARB Twin on Board Compressor
Our ARB Twin on board compressor is the best compressor we have ever owned. It is an absolute beast, and we would highly recommend this compressor. They are expensive but they do the job, and they do it quickly. We have mounted this on the side of rear drawers under one of the side wings. We do not store anything else under here to ensure the compressor gets enough air flow. If it is a hot day, we open the rear driver side passenger door for more air flow. The wiring of the ARB compressor is straight forward as it comes with detailed instructions and all the wiring and fuses. It is just a matter of connecting the cables and connecting them to power as well as the switch. This runs directly off our second battery with the on off switch at the rear of our drawers.
Oricom UHF
Our Oricom UHF is also connected to our second battery rather than our starter battery. We chose to do this so that we can have it turned on when the car is completely off. This is a great idea as it allows you to stay in coms with others without having to keep your ignition on and risk draining your starter battery. This was extremely simple to wire up. You basically connect your positive to your fuse box and your negative to the earth block and you are good to go.
Trailer Power
The final thing we connected to our second battery setup was the power to our camper trailer DOT373. This is the grey anderson plug sitting just above our towbar. It was far easier running power from the second battery for the trailer as this setup is all in the rear.
We hope you have enjoyed reading about our 4WD dual battery 12V electrical setup. If you have any questions or comments please comment at the bottom of this post and we will respond. For more posts on the electrical setup in our 76 (70) Series Toyota Land Cruiser read them here.
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Thanks for reading legends.
The thoughts of Peter.
08/09/2021 @ 9:07 PM
What a great article!!
I am looking at setting up my car with a 12V setup and this has given me so many great ideas!!
I would be interested in what size wire you are running through out and where you have got all of your main fuses located!!
09/09/2021 @ 4:45 PM
G’day Kieran,
Thanks for the feedback mate, really appreciate it.
Wire sizes change depending on what they are being used for. So for example, the wires for our 12V outputs (USB etc) are around a 3/3.5mm wire. You can probably go smaller but just check the rated Amps on the wires and compare this to the 12V item you are installing. For our inverter the wires are massive due to the amount of Amps being drawn from the battery. All our accessory fuses for everything connected to the second battery are located beside the battery. You should be able to see the fuse box in the header image of this post just to the right of the battery. Fuses for the inverter and DCDC charger are larger fuses so these are mounted out of the way on our drawers.
Hope that helps mate.
Cheers,
Peter