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Having the right 12 volt set up is critical to enable me to spend long lengths of time off-grid. I need power to run my fridge, my freezer (on long trips), lights and more importantly to recharge my laptop and camera batteries. Then there are things like Bluetooth speakers, iPods, torches, portable battery packs, air compressor and pie warmer.

Keeping it simple is also important as it makes troubleshooting easier. I prefer items that have minimal moving parts and are dust, heat and moisture proof. I am quite happy with my current setup, and here is what I have done.

Two batteries in the engine bay.

I currently have 2 x Supercharge All Rounder MRV70 batteries that have 760CCA (cold cranking amps) and are 105Ah deep cycle capability. These batteries are calcium lead acid and are a transition battery between a shallow cycle starter battery and a true deep cycle battery.

They have handled the corrugations and hot temperatures better than other brands of batteries I’ve used and I will swap them with my camper trailer batteries shortly as they are almost three years old now and will enjoy a rest in the camper trailer.IMG_6621

These batteries are linked via a Projecta 200amp Voltage Sensitive Relay (VSR), a simple but effective way of connecting two batteries of the same type together and controlling the charging of each. The VSR cuts in once the main battery has reached 13.4v and cuts out when the main battery reaches 12.8v. It allows the alternator to replace the energy my main battery lost on starting the engine before it begins sending any charge to the auxiliary battery.

The important thing to note is that for a VSR to work correctly, two batteries of the same type must be connected. It wouldn’t work if my auxiliary battery was an AGM, Gel or Lithium battery, I would need a DCDC charger in this scenario.


My main battery is responsible for firing up the engine, running the winch, powering the headlights and spotlights, keeping the stereo running and all the other little electrical chores that are factory default. My auxiliary battery is responsible for powering my fridge, LED camping lights, and miscellaneous 12v power points. When my camper trailer is connected, the VSR in the camper is connected directly to my main battery via a circuit breaker.

I have a third battery!

What the? Why do I need a third battery?

When it comes to power, the most important piece of equipment I have is a pure sine wave inverter. Pure sine is critical as the power it provides is the closest to homegrown 240v that I can get, important in protecting my camera batteries and laptop when recharging. I run this off a third battery because I don’t want the inverter to be chewing valuable power from my main or auxiliary batteries.

My third battery is of the AGM (Absorbent Glass Mat) variety and provides me with 130ah when full. The advantages of the AGM over my calcium lead acid is that they offer slower self-discharging rates, don’t discharge corrosive gas and handle vibrations better.

This AGM battery is connected to my main battery via a Projecta IDC25 24A 3 Stage DCDC charger. This not only has the smarts to work with traditional and smart alternators, but it provides a comprehensive multi-stage charge that will improve my battery’s performance as well as allowing me to recharge the battery by connecting directly to my solar panels. Not only can the IDC25 charge my AGM, but it can handle calcium, wet and gel batteries too.

Solar Challenge


The challenge when driving remote tracks at low speeds for hours upon end is for the alternator to provide enough power to recharge my batteries. In most cases, it can’t and so alternative solutions need to be found to help out.

Projecta supplied me with a 180w folding solar panel kit to solve my problem and solve my problem it did. Most afternoons I was pumping 10 amps into my batteries! The monocrystalline panels were sucking so much power from the sun, it would disappear beyond the horizon each day to recuperate. The solar controller has a 4 stage charging setup so my batteries can’t be overcharged and when the batteries are full it goes into “floating” mode, topping up the batteries when needed.

For me, this set up is currently perfect. I survived over 24,000km with enough power to keep everything running. I did have an issue with the folding solar panels that I left home with, but they were a different brand and ended up in the bin. Thankfully, Projecta were happy to ship their panels to me in Alice Springs and I was able to cross the Simpson Desert via the Madigan Line without worrying about my batteries.


Please note that Projecta are a sponsor, however this blog was not written with that in mind.

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