The sealed lead-acid battery in the back of your caravan was state-of-the-art in 1996. Three decades on, lithium iron phosphate batteries have reset the rules: half the weight, four times the cycle life, and the full nameplate capacity available for use rather than the half you got from an AGM before the voltage sagged. The shift from lead-acid to LiFePO4 is what turned a weekend power supply into something a grey nomad can live off for a fortnight without thinking about it.
This is a build guide rather than a chemistry lecture. By the end, you should be able to size, specify, and wire a 12V lithium solar system that suits your caravan, camper trailer, or 4WD without overcapitalising or undercooking it.
The Four Parts of a Working System
Strip the marketing back, and a 12V lithium solar system is four things bolted together. A LiFePO4 battery stores the energy. A DC-DC MPPT charger takes power from your vehicle’s alternator and your solar panels and feeds it into the battery at the correct voltage. The solar panels capture sunlight. And an inverter, if you choose to fit one, turns 12V DC into 240V AC for residential appliances.
Cables, fuses, and an isolation switch are not optional accessories. They are the difference between a tidy install and a melted one.
VoltX SRNE 12V 50A DC-DC MPPT LiFePO4 Battery Charger with Bluetooth
Sizing Your Battery: Start with What You Actually Run
The biggest mistake first-time builders make is buying battery capacity without first calculating their daily load. Work the other direction.
A 60-litre 12V camping fridge in mild weather draws roughly 30 to 40 amp-hours per day. Two LED interior lights for four hours add another five to eight. A water pump on demand is two to four. Phone, tablet, and camera charging across an evening is another five to eight. A typical weekender lands at 50 to 65 amp-hours per day.
A VoltX 12V 100Ah LiFePO4 stores 1,280 watt-hours of real, usable energy, and weighs 10.8 kilograms. The same capacity in AGM is roughly 30 kilograms and is only half usable before the voltage drops too low for the load. For a weekender running fridge, lights, phones and a water pump, a single 100Ah is enough to coast through a day and a half without solar input, and indefinitely with even modest solar replenishment.
Here’s what one of our customers said:
“This is my 2nd purchase of this type of battery from Outbax. These 2 are for my caravan, I have a 300amp which is now 3+ years old and still going strong in the 4wd.”
If you also run a CPAP overnight, a diesel heater fan, an inverter for short bursts of induction kettle, or a residential-style fridge, you are not looking at one battery. You are looking at two 100Ah batteries in parallel, or stepping up to a 200Ah battery.
A simple rule of thumb: total your daily amp-hours, multiply by the number of cloudy days you want to survive without sunlight, and that is your minimum battery bank. Most Australian touring routes let you assume one cloudy day in three.
VoltX 12V 300Ah Pro Lithium LiFePO4 Battery
Choosing Your Battery
Inside the VoltX 100Ah range, four variants suit different builds. The standard 12V 100Ah LiFePO4 deep-cycle is the default. It carries grade-A prismatic cells, a built-in BMS, IEC 62619 certification, a three-year manufacturer warranty, a 60-day money-back guarantee, and a service life rated at up to 4,000 cycles. For most caravan and camper builds, this is the battery to start with.
The Pro range, like the VoltX 12V 200Ah Pro Lithium battery, extends the warranty to 60 months and is the right choice for full-time off-grid travellers who plan to wear the battery hard. The Bluetooth Smart variant adds a DALY smart BMS and can be monitored via a phone app, which matters if you want real-time pack data without buying a separate shunt and display. The Slim form factor found in the VoltX 12V 200Ah Slim LiFePO4 battery is the answer for 4WD canopy and tight space caravan installs, where the standard footprint will not fit.
Most VoltX batteries support series and parallel connections of up to six packs, but the maker is unambiguous on one point: never mix lithium batteries of different brands, ages, or charge states in the same bank. The BMS units fight each other, and the weakest pack ages all the others.
Here’s what one of our customers said:
“I’ve had this battery connected in parallel for about a year feeding a 2.5KW inverter and they have worked faultlessly over this time. Have been off grid for 4 days running aircon for about 3 hrs a day, as well as air fryer, coffee machine and everything else that runs off the 12v side, with 650 watts of solar and by the end of the week we still had 100% on battery. excellent buy and excellent quality.”
Charging: DC-DC MPPT Versus Solar Regulator
This is where most builds go wrong. If you are charging from your vehicle’s alternator (and almost any caravan or 4WD setup will be), you need a DC-DC charger between the starter battery and the auxiliary lithium. Modern Australian utes, including the current generation Hilux, Ranger, Amarok, and BT-50, run smart alternators that throttle output for fuel economy. A LiFePO4 battery never sees the voltage it needs to fully charge directly off these alternators.
The VoltX SRNE 12V 30A DC-DC MPPT covers a single 100Ah build. The 50A version is the right unit for a 200Ah or two 100Ah parallel bank. Both are dual-function, accepting solar input on the same unit, so you do not need a separate solar regulator unless your panel array exceeds the controller’s input capacity.
If you have a stationary off-grid setup with no vehicle alternator, a standalone MPPT solar charge controller is the simpler choice. The VoltX 20A and 40A MPPT controllers handle most camping arrays at 99 per cent tracking efficiency and accept lithium, AGM, gel, and flooded chemistries from the same unit.
Solar Charge Controller 30A 12V/24V/36V/48V MPPT with Bluetooth
Solar Panels and Where to Mount Them
Typically, a 200-watt panel, like the VoltX 200W Solar Panel, is enough to keep a single 100Ah topped up under typical Australian conditions. Three to four hundred watts handles a 200Ah bank. Six to eight hundred watts is the territory of full-time off-grid vans running residential loads.
Fixed roof panels are the most efficient per dollar, but commit you to wherever the van or canopy is parked. Folding portable panels let you chase the sun while the van stays in shade, which can matter more than nameplate wattage in summer. Solar blankets are the lightest option for tents and rooftop tents.
VoltX 12V 130W Fixed Solar Panel
The Wiring Rules That Catch Most People Out
There are three essential rules in wiring battery systems. Get them right, and the install lasts a decade. Get them wrong, and you will be replacing a controller before your first long trip.
First, when you connect the system, the order matters. Battery first, then panel, then load. Connect the panel first, and the controller can be damaged by open circuit voltage with no battery to absorb it.
Second, size your cabling for the run length, not just the current. A 50A DC-DC running between starter and auxiliary battery in a long wheelbase ute should not be run on cable thinner than 6 B&S. Voltage drop on undersized cable is the silent killer of charge performance.
Third, fuse on the positive side as close to each battery as physically possible. An isolation switch is part of the build, not an upgrade for next year. If anything ever goes wrong, those two components are how you stop a fault from becoming a fire.
The Mistakes That Cost Real Money
Charging a LiFePO4 battery with a lead-acid charger that has no lithium profile destroys cells over time. Mixing battery brands in parallel triggers BMS conflicts within months. Running a 1,000-watt inverter from a single 100Ah battery at full load drains it in under an hour. Charging a lithium battery below freezing without a heater pad damages cells permanently. Skipping the DC-DC charger on a smart alternator vehicle means the battery never reaches a full state of charge, no matter how long you drive.
None of these are exotic problems. They are the daily inbox of every battery retailer’s support team.
The Standard Build
For most caravan and camper trailer owners reading this, the answer is one VoltX 12V 100Ah LiFePO4, one VoltX SRNE 30A DC-DC MPPT charger, 200 watts of monocrystalline panel, appropriate cabling and fusing, and an optional 600-watt pure sine wave inverter if you need 240V at the campsite. For 4WD canopies, swap the standard 100Ah for the slim variant. For full-time off-grid vans, double the battery bank, step up to the 50A DC-DC MPPT, and budget for 400 watts of panel as a minimum.
Build it once. Build it properly. The VoltX range ships from Outbax’s Sydney warehouse with a 60-day money-back guarantee, so the only thing standing between a planning weekend and a finished system is whether you have measured the canopy or battery box for clearance before you click buy.
