DIY – 12V Electrical Power

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Power On

12V appliancesThere is an enormous range of 12V appliances and accessories available for Campervans and Motorhomes, all requiring a reliable 12V power supply.

Your Campervan or Motorhome needs three things for a reliable and sustainable 12V power supply:

    • adequate battery capacity to power all appliances;
    • adequate battery recharging sources, including appropriate regulators;
    • appropriate cabling and connection of appliances and devices to the battery.

All these bits and pieces can be installed permanently or fitted temporarily. Regardless of which option you choose, all your 12V appliances must be connected to the power supply with suitable gauge cable and robust (and correctly fitted) cable terminators and plugs, for both safety and functionality.  This is important – in some applications it is critical.


More 12V info…


Your 12V ‘house’ appliances are powered independently from your vehicle’s starting battery, though the battery/s powering your appliances can still be recharged from your vehicle’s battery charging system using an isolator / regulator.

This video provides a good overview of 12V off-grid equipment options:

Listed below are some DIY options for providing and maintaining a 12V power supply in your Campervan….

* Prices are approximate and are in AUD | *Links are to examples of the device category
Before you start…

Battery capacity? Check your appliances’ rate of consumption of electrical current (amps) – this will determine the type of battery (AGM or Lithium) and the storage capacity (Ah) required for a Power Station or battery.

Basic schematic layout

A 120Ah Lithium battery has a ‘usable’ capacity of around 96Ah (80% of specified capacity*). A 12V fridge drawing 2 amps (when the compressor is running) will deplete 1.5 Ah per hour from your battery, so you have a ‘safe’ runtime of around 65 hours from a fully charged 120Ah Lithium battery (with no recharging).

A 120Ah AGM battery has a ‘usable’ capacity of around 60Ah (50% of specified capacity). The same 12V fridge, consuming 1.5 Ah per hour will have a ‘safe’ run-time of around 40 hours from a fully charged 120 Ah AGM battery. You can estimate when an AGM battery has reached its 50% charge capacity when the voltage drops to 12.1V.

AGM and Lithium battery charge levels

* Some Lithium battery suppliers claim 100% usable capacity. Maybe. Let’s play it safe and stick to a guideline of 80%, which will ensure battery operability and a longer life-span.

Battery Charging – Of course, the estimated appliance run-times above are based on the initial capacity and subsequent discharge rate of a fully charged battery. Deep-cycle batteries can be recharged to restore their capacity and significantly extend the run-time of your appliances.

Solar charger battery and fridge

Your batteries can be recharged with electrical current generated from a solar panel, the vehicle alternator, or a 230V mains supply, via an appropriate charger / regulator, which can extend your appliance run-times indefinitely, if you have enough recharging capacity.

Thinking of an inverter? Inverters are used to run portable 230V AC appliances from your 12V DC battery/s.

However the amps drawn from a 12V battery by domestic 230V appliances operating through an inverter can be huge – calculated (approximately) by dividing the power draw of the appliance (Watts) by 10. For example, a 700W toaster will draw around 70 amps, consuming around 1.2 Ah per minute from a 12V battery.

Battery and inverter with toaster and current draw

A low wattage inverter (under 1000W) connected to a battery with 100Ah or less in capacity is more suited to charging laptop computers, running CPAP machines, etc, rather than powering larger domestic appliances. A battery’s capacity to supply a high continuous current is a consideration here too – Lithium batteries are an advantage in this scenario.

Copper Cable12V cabling – There is cabling and there is cabling. If you want reliable 12V power you MUST use quality cable and cabling techniques to hook everything together. There must be a suitable gauge cable path for electrical current to move from your battery to your appliances, and back again, without any cabling hindrances.

12V Power – Option A:  Portable Battery Box

Battery BoxA deep-cycle battery, fitted in a powered Battery Box is probably the easiest 12V power option to get up and running. It is also relatively cheap, especially if you already have a battery.

Powered Battery Boxes hold your battery securely, providing external connections for Anderson plugs, 12V cig sockets, USB sockets, and screw terminals. They are also fitted with a voltmeter, which can be used to estimate how much charge you have left in the battery.

If you fit an AGM battery, and include a 230V charger in your kit, a Battery Box option is probably the cheapest portable 12V power option.

For overnight or weekend trips, running only a fridge and mobile phone charger, it is likely that, with decent battery capacity, you may not need any on-site re-charging….

Temporary 12V basic box schematic

See also: Portable fridge & 12V power on the go >>>

For longer trips, a solar panel and/or 12V DC-DC charging facilities will provide longer battery runtime….

Temporary 12V advanced box schematic

Kings Battery Box

Battery Box – Option 1

Adventure Kings Battery Box(Holds 120Ah AGM or Lithium battery) – Includes 2 x 30A Anderson plugs, 2 x USB outlets, 1 x 12V cig socket, 2 x screw terminals, 1 x Voltmeter, isolation switch, resettable circuit breaker. (~$60)

iTechWorld Battery Box

Battery Box – Option 2

iTechWorld GoFurther Box(Holds 120Ah AGM or Lithium battery) – Includes 1 x 175A Anderson plug (for Inverters, etc), 4 x 50A Anderson plugs, 3 x QC 3.0 USB outlets, 1, USB-C outlet, 2 x 15A 12V cig socket, 2 x screw terminals, 1 x LCD screen, isolation switch, 2 x 50A auto-reset circuit breakers. (~$300)

iTechWorld battery box

Battery Box – Option 3

iTechWorld GoFurther Box & Charger(Holds 120Ah AGM or Lithium battery) – Includes a 25A DCDC Charger (with 1 x Triple Anderson plug for DC-DC ignition source input & 1 x 50A Anderson plug for DC-DC MPPT solar input), 1 x 175A Anderson plug (for Inverters, etc), 4 x 50A Anderson plugs, 3 x QC 3.0 USB outlets, 1, USB-C outlet, 2 x 15A 12V cig socket, 2 x screw terminals, 1 x LCD screen, isolation switch, 2 x 50A auto-reset circuit breakers. (~$600)

However, if you are considering a Lithium battery, with AC and DC chargers, and maybe an inverter, along with the various plugs and fittings, and vehicle installation, it may not be worth the effort (and cost) when compared to the simplicity and functionality of a Portable Power Station….
12V Power – Option B: Portable power station (the easy option!)

Power stationIf you are planning on a basic van setup, with a bed, a fridge and a portable water supply for weekends away, then a self-contained power station is without any doubt the easiest way to get up and running with a reliable 12V power supply.

These power stations have become a more widely available option in recent times with the advent of affordable Lithium batteries and good quality power inverters.

A portable power station provides a reliable 12V power supply for your fridge and other 12V accessories (lights, fan, etc), along with the option of 230V for small appliances (like a sandwich press) and USB charging points for all your portable devices – as well as all the required built-in infrastructure for re-charging the power station battery from the vehicle alternator, a 230V mains supply, or a solar panel – all contained in a single portable box.

They can be used during the week for power on a worksite or in the back yard, then double up as a camping power supply on the weekends. Larger models can even run your domestic household appliances (eg – freezer) for short periods in the case of a power outage.

The only decision to make is how big do you want to go (and how much money do you want to spend).


What size Power Station?

To be able to compare ‘apples with apples’,  dig into the specs and find the capacity of the Lithium battery that is running the show – in Amp Hours (Ah) @ 12V. 

Power station sizes

For power stations rated in Watt hours, divide this by 10 (and subtract a little!) to get an idea of the Ah capacity of the battery. (Divide by 12 for a more accurate measure.) A 500Wh power station is likely to have a battery capacity of around 42Ah.

A 500Wh / 42Ah  power station has a usable capacity of 34Ah (80%) and will keep your fridge, consuming 2 Ah per hour, cold for around 17 hours. This is about the minimum battery capacity to be useful for any time off the grid. 100Ah battery capacity would be better for longer stays.

If your fridge is under 50L capacity, the weather isn’t too hot, and the fridge is only consuming 1 Ah per hour, then you might be getting closer to 30 hours runtime from a 500 Wh power station.

But don’t even think about plugging a 230V fridge into the 230V socket on a portable Lithium power station – only use a 12V fridge! (Unless you have a huge inverter designed for this sort of domestic backup use.)


Temporary 12V power station schematic

25Ah Power pack

Power Station Option 1
Self-contained Lithium power station – 25Ah 
– At the most rudimentary level, this might be all you need for short overnight excursions. Includes an AC inverter (300W) and a variety of outlets – 230V, 12V and USB. Recharge from 230V, car, or solar. (~$400)

50 Ah power station Power Station Option 2
Self-contained Lithium power station – 50Ah 
– A medium capacity Lithium ‘Power Station’ for longer run times for refrigerator, LED lights, fans, etc. Includes an AC inverter (PSW – 500W) and a variety of 230V, 12V and USB outlets. Recharge from 230V, car, or solar. (~$900)

100Ah Power station

Power Station Option 3
Self-contained Lithium power station – 100Ah 
– A larger capacity Lithium ‘Power Station’ for extended run times for refrigerator, LED lights, fans, etc. Includes an AC inverter (PSW – 1300W) and a variety of 230V, 12V and USB outlets. Recharge from 230V, car, or solar. (~$2300)

Larger capacity portable power stations are also available, but they do become expensive! See Goal Zero >>>

Solar Power Station Power Station Option 4
Lithium power station (50Ah) + Solar panel
– Combine a self contained power station, built around a Lithium battery with a built-in 230V inverter, and a 200W solar blanket. Outlets for 230V AC, 12V DC and USB. Built-in lithium battery recharges from solar / 12V / 230V (~ $1500+ AUD)
12V Power – Option C:  Permanent battery and charging installation

For a more permanent setup, a battery (or batteries) can be tucked away in a cupboard or under the bed, and wired permanently into the electrical system of the van. This is the most common setup in a Campervan or Motorhome.

In addition to the battery/s you will need a battery charger and wiring infrastructure to connect your camping batteries into the electrics of the vehicle, to provide for the alternator to charge the batteries when the engine is running.

Note: As a result of new Australian Design Rules (ADR), introduced in late 2022, it is likely that you will also need a vented ‘battery closet’ in which to mount and store the battery/s, so they are sealed from the house area of the van. More info here when implications of the new ADRs are clear, and commercial products to meet these needs are available.

Overview schematic diagram of campervan cabling

You basically have two options for a permanent battery – an AGM battery or a Lithium battery.

Lithium is the way to go if you can afford it. They cost about $900 for a good quality 120Ah battery compared to around $300 for a similar capacity AGM battery. But they are half the weight (no lead) and provide a more consistent and longer lasting 12V power supply. (There are cheaper Lithium options available – around $500 – though there are questions around the performance of these cheaper batteries over time, especially when operating under regular high-current-draw conditions.)

More info about batteries >>>

Deep cycle 120Ah battery Option 1
Permanent battery – 120Ah
 – A permanently fitted deep-cycle AGM or Lithium ‘house’ battery (100Ah+) will power a 12V fridge, lights, TV, water pump, etc. ($300 for AGM to $1000 for Lithium). Recharge from alternator, solar panel or mains power. (Battery chargers/regulators required).

Deep cycle 120 Ah batteries

Option 2
Larger battery capacity – 240Ah
 – Multiple deep-cycle AGM or Lithium batteries connected in parallel, providing more than 200Ah capacity, will enhance the off-grid capacity of your 12V power supply. Recharge from alternator, solar panel or mains power. (Battery chargers/regulators required.)

Single 200 Ah and 300 Ah Lithium batteries are also available – check the installation space you have available.

Battery Recharging

Your battery/s need to be recharged to maintain their energy supply.

Each of the options below can be used to recharge your house battery/s. A combination of all the options below will provide flexibility to be able to recharge your battery/s in various environments.


Charging batteries from the alternator? The videos below are worth a look to get a general idea of what might be required for a DIY 12V installation with dual batteries (engine starter battery and auxiliary ‘house’ battery)….. 

Kings dual battery videos (YouTube)


Alternator Option 1
Vehicle Alternator
– Your vehicle’s alternator is charging the starting battery whenever the engine is running. Harness the output from your alternator (via a suitable isolator/regulator) to recharge your Campervan house battery. Read more about Battery Charging >>>

Solar Panel

Option 2
Solar panels
(5-15 amps output) – Recharge your house batteries from sunlight, to provide a sustainable power supply for longer-term off-grid camping. Choose either portable folding panels or a blanket, or a fixed panel on the roof of the van. Look for at least 150W rating.  (300W capacity recommended for longer-term free-camping.) Use in conjunction with a suitable regulator, as below. Many options available, from $200.

240V socket

Option 3
AC Mains Power – When staying in a formal campground with site power, charge your batteries from mains power, via a suitable charger/regulator and a circuit breaker.

Important: Mains power connections to your van must be installed by a licensed electrician.

Charging regulation
You need a battery charger / regulator to adjust the output of the charging source (solar panel, alternator, 230V) to suit the charging requirements of the battery/s.

Solar controller

Option 1 – Solar panel only
Solar Regulator
– (Up to 10 amps output, depending on panel size and sun availability) Most portable solar panels are supplied with a charger to connect your panel to the battery. If you have a choice, choose an MPPT charger rather than a PWM charger. ($50 – $400)

Look for an Anderson plug connection rather than alligator clamps to connect to the battery.

Not required if you are charging a power station that has a built-in solar charger.

Redarc BCDC charger

Option 2 – Vehicle alternator + Solar panel
DC-DC Regulator
(20 – 50 amps output) – A DC-DC regulator manages the recharging of your ‘house’ batteries from multiple DC (Direct Current) sources – alternator and/or solar panel – to provide the correct charging voltage and current to your house batteries, while preventing appliances from depleting your starting battery. (Wide variety of options – $300 – $800.)  

CTEK M25 Charger

Option 3 – Mains Power
AC-DC Charger 
(20 – 40 amps output) – An AC-DC charger manages the recharging of your house batteries from a mains AC (Alternating Current) power supply. ($350 – $550). 

Important note: Mains power installations must be carried out by a licensed electrician, with an appropriate circuit breaker installed.

Battery Isolator

Very basic – Vehicle alternator only
Battery isolator / VSR
(Not recommended, especially when charging Lithium batteries, or in post-2006 vehicles with ‘smart’ alternators.) Relatively straightforward to install and setup. Recharge your house battery and vehicle battery from the vehicle alternator while the engine is running, but ‘isolate’ your vehicle battery, so as not to deplete its stored energy, when operating the refrigerator, lights, etc from the house battery. ($30 – $100) 

The Hookup
12V Basics

Nothing else matters if you don’t get this right…

Installing a battery, a charger, a solar panel and a fridge is the easy part. Connecting it all together requires careful planning, based on an understanding of good electrical installation practice.

Other stuff
Distribution panel Gauges, panels & outlets – Use a distribution panel with a built-in voltage meter to monitor your battery state of charge (AGM batteries) and to provide outlets to connect various portable devices. Wide variety of options available. From $100.

Battery monitor - percentage Fitting a Battery Monitor – Check % battery charge (SoC), incoming and outgoing current, voltage and remaining battery capacity. Can be used for both AGM and Lithium batteries. ($50 – $200)

Inline power meter Inline Power Meter – Connect between your portable solar panel / regulator and battery to measure how much current is being returned to the battery from the solar panel. ($30)

Inverter Installing an Inverter – Run 230V appliances from your 12V power supply. (There are some limitations – read more here.) ($200 – $1500)

Fuse box Fuse box – Provide a fuse link for each permanently installed 12V appliance. Various options available from most RV parts shops.


More detailed info about a sustainable 12V power supply:

See also:


DIY Fit-out | What size van?Draw a floor planCabinet materials | Fittings | 12V power