Lithium and Solar for Australian Caravans: What You Actually Need | VANTURE

There's a question asked in every caravan forum in the country, and it's the wrong question.

"How many batteries do I need?"

Nobody can answer it. Not the bloke at the caravan show, not the YouTube channel with the beautiful build, not us. The answer depends entirely on what you switch on, how long you leave it on, and where in Australia you are when you do it. A couple running a 12V fridge and some LED lights in Queensland in October have almost nothing in common with a couple running a diesel heater and a CPAP machine in Tasmania in July — and yet they'll get handed the same shopping list.

The good news: the right question is answerable, at the kitchen table, with a pen and twenty minutes. This guide walks through that, then covers the safety rules that changed in Australia in 2023 — because a lot of what's online predates them.

One thing up front: this is not a how-to-wire-it guide. There's a line between understanding your system and installing it, and we'll be clear about where it sits and why.

Start with what you use, not what you'll buy

Every honest off-grid system starts with an energy audit. It's the least exciting part and the only part that matters.

Here's the whole of the arithmetic. Watts × hours = watt-hours — the energy something uses. Amp-hours × volts = watt-hours — the energy a battery holds. Work in watt-hours and you can compare anything to anything; work in amp-hours alone and you'll eventually compare a 12V number to a 24V number and get a wrong answer.

So: list everything that draws power. Not the things you imagine using — the things you actually use. For each one, write down what it draws and how many hours a day it runs. Your fridge's compressor doesn't run 24 hours a day, so use its realistic duty cycle rather than its rated draw times 24; if you don't know it, the manufacturer usually publishes a daily consumption figure, and that's the number to use.

Add it up. That total — your watt-hours per day — is the most important number in your build, and it's yours, not anyone else's.

Now do it again for your worst case. The cold week. The wet fortnight where nobody goes outside and everything runs longer. Design for that, not the average, because the average is not when your system will let you down.

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The battery: nameplate is not what you get

A battery's advertised capacity and the energy you can actually take out of it are two different numbers.

Every chemistry has a depth of discharge it tolerates before its life shortens — and lead-acid and lithium are not remotely alike here. That's the real reason people move to lithium, and it's a better reason than weight: for a given nameplate capacity, you get meaningfully more usable energy out of a lithium bank, and it doesn't mind being cycled deeply the way lead-acid does.

We're deliberately not printing a percentage for either. Depth of discharge varies by chemistry, by manufacturer and by how long you want the thing to last, and the honest source is the specification sheet for the actual battery you're considering — not a rule of thumb from a forum. Ask the supplier for the usable capacity and the cycle life at that depth of discharge. A supplier who can answer that clearly is telling you something useful about their product. So is one who can't.

Two things worth knowing before you shop. Lithium has a temperature problem, and Australia has temperature — most lithium chemistries should not be charged below freezing, and heat shortens their life, so where the battery lives matters as much as which battery it is. And a battery is not a system: it needs charging, protection, monitoring and somewhere legal to live. It's usually the cheapest part of that list to get right and the most expensive to get wrong.

The solar: the number on the panel is a laboratory number

Panels are rated at Standard Test Conditions — a defined lab benchmark. That rating is useful for comparing one panel to another. It is not what your roof will make on a Tuesday.

Real output moves with the season, your latitude, the angle of the panel, the temperature (panels get less efficient as they get hotter, which surprises people in exactly the country where it matters most), and — most brutally — shade. A small shadow in the wrong place can cost far more than its size suggests. That gum tree you parked under for the shade is also the reason your batteries didn't fill.

Two consequences that matter more than panel brand:

Winter is the design case, not summer. Shorter days and a lower sun mean less energy, and it's also when the heater runs. Size for January and it will disappoint you in July. Size for July and January is a holiday.

Roof space runs out before your ambitions do. Hatches, aircon and vents are already using some of it. Worth measuring before you plan.

We're not printing "you'll get X watt-hours per day from a Y watt panel." Nobody can, honestly, without knowing your location, month and shading — and a figure like that from a national marketplace would be a guess dressed as advice. A good installer will model it for your actual set-up.

And there's the honest alternative nobody wants to hear. If you sit in one shaded spot for a week in winter, no reasonable amount of roof solar will keep up. That's physics, not a failure. A portable panel you can put in the sun while the van stays in the shade solves more problems than another rooftop panel — and a generator, or a night on mains, is not a moral failure.

What changed in 2023 — and why the internet is out of date

This is the part that matters most, and the part most likely to catch out someone copying a build they saw online.

Electrical installations in caravans, motorhomes and camper trailers are covered by an Australian Standard: AS/NZS 3001.2:2022. It was published on 18 November 2022 with a 12-month transition, during which the old AS/NZS 3001:2008 remained current. From 18 November 2023, the new standard took over.

That timing is the trap. A build video from 2021 or 2022 can be a perfectly good video and still show an installation that would not be built that way today. The creator wasn't wrong. The rules moved. That's a big part of why "I saw a bloke on YouTube do it" is a risky basis for a lithium retrofit right now — and why an installer quoting more than you expected may simply be quoting you the current standard.

The Caravan Industry Association of Australia holds a seat on the Standards Australia committee for AS/NZS 3001 and worked with state associations and industry through the revision. It's worth saying plainly: this was the industry helping write safer rules for its own customers, not something done to it.

Here's what the standard requires for the batteries that run your living space. (It doesn't cover your vehicle's starting battery — that's a different thing under different rules.)

For every house battery:

It must be rechargeable, with a minimum capacity of 40Ah at a 20-hour discharge rate.
Terminals must be clearly identified — durable +/– markings or colour coding — and connections must be securely clamped or bolted and insulated.
It must be restrained so it cannot move more than 25mm in any direction under a pulling force of twice the battery's weight, applied through its centre of gravity. This is a crash-and-corrugation requirement, and it's the one most obviously missing from a lot of DIY installs.
Each battery bank must be protected against short circuit and overload by fuses or circuit breakers in each unearthed pole, accessible but protected from accidental damage, and located close to the battery terminals.
No more than four conductors on any single battery terminal.
Metallic service lines — gas, diesel, water — must be at least 300mm clear of the battery surface containing the terminals, or shielded with dielectric material.

For lithium-ion specifically:

It must be located externally — that is, behind a wall, compartment or barrier that prevents any vented gases entering the living area. Not under the bed, in the open, with the doona.
The installer is required to consult the battery manufacturer and supplier to confirm a compartment and venting design appropriate for that battery type. This is explicitly not a one-size-fits-all box.
The location must keep the battery within the manufacturer's defined operating temperatures and IP rating.
If the manufacturer hasn't provided encapsulated cells, the battery must be installed in a suitable container.
The battery must comply with AS IEC 62619.
It must have a battery management safety system — integrated into the pack or separate — located no more than 600mm from the battery, continuously monitoring and protecting against over- and under-voltage, over- and under-temperature, and over-current. It must come from the same manufacturer as the cells, or be in line with their recommendations.
It must be monitored by a battery monitor designed for lithium-ion, displaying state of charge.

For lead-acid, there's a spill tray holding at least 20% of the electrolyte, easy access for maintenance, and ventilation rules depending on whether the battery lives inside or out — internal batteries must sit in a compartment vented outside, with any opening into the living area sealed.

The standard also introduced requirements around protecting and isolating solar arrays. We're not printing the specifics: we couldn't verify them to the standard itself, and a half-right fusing instruction is worse than none. Ask your installer to walk you through how your solar side is fused and isolated. If they can explain it, that's a good sign.

One more line in the standard is worth quoting for what it says about the spirit of the thing. Where a van has no provision for a battery, the instructions must read: "This vehicle has not been designed to accommodate a vehicle battery. Do not fit one." Not "be careful." Do not fit one. Some vans aren't built for it, and adding one anyway is not a small liberty.

The line we're not going to cross

Anything at 240V must be done by a licensed electrician. Not "should be." Not "unless you're handy." The standard itself requires that installation instructions direct the work to an appropriate person — a licensed electrician — under the electrical legislation of your state or territory, and those requirements are not identical everywhere.

This isn't us being precious. 240V in a metal box on a dirt road, wet, hundreds of kilometres from a hospital, is an unforgiving environment. Bad 240V work in a caravan also has a habit of surfacing years later, in someone else's hands, after you've sold it.

We're also not going to give you 12V wiring instructions. Extra-low-voltage work sits differently in the law and people do their own — but "differently" is not "freely", it varies between states, and a lithium bank can deliver an enormous amount of current into a mistake very quickly. What you personally may and may not do to your own van is a question for your state's electrical safety regulator — and it's better asked before you buy the parts than after.

One compliance point people miss when they retrofit: the new standard applies to systems installed or significantly modified after 18 November 2023. Swapping lead-acid for lithium isn't a small tweak — it's exactly the kind of change that brings the current standard into play, including the external-location requirement.

Find someone licensed near you. VANTURE's services directory lists caravan and motorhome businesses across Australia — including auto electricians and solar installers. Find a service provider on VANTURE · How the services directory works

The weight nobody budgets for

Batteries, panels, inverters, cable and mounting hardware all weigh something, and every gram comes out of your van's payload — the gap between what it weighs empty and its ATM.

This is the quiet cost of a big off-grid build. A serious system can consume a meaningful slice of a van's payload before you've loaded a single shirt, and none of it appears on the compliance plate, because the plate was stamped before the system existed. If you're retrofitting, you're changing your van's real-world weight and nobody is tracking that but you. So track what you add, and weigh the van afterwards — a weighbridge is the only thing that tells you the truth.

If any of that is unfamiliar, our complete GVM, GCM and ATM guide is the deep version, and Understanding ATM, GTM and Tare Weight is the short one.

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Buying a van that already has a system

Most people don't build from scratch — they buy a van with something already in it. Five questions, all better than "how many batteries has it got?"

When was it installed, and by whom? The 18 November 2023 date is the one that matters. Before it, the older standard applied — which doesn't make the van unsafe, but you're looking at a different set of rules, and that's worth knowing rather than assuming. Ask too whether it was factory-fitted or retrofitted: both can be excellent, but a factory system was designed into the van and a retrofit was designed around it.

Where does the lithium battery live? Thirty seconds to check yourself. If it's lithium and it's sitting in the living space without a sealed, externally-vented enclosure, that's a real question to ask — politely, because plenty of sellers genuinely don't know what's under their own bed.

Is there a battery management safety system, and a monitor showing state of charge? Both are required for lithium under the current standard. The monitor is the easy one to spot.

Is there documentation? Certificates for any 240V work, the battery's spec, the installer's details. A seller with a folder is telling you something good. A seller without one isn't necessarily hiding anything — but you're buying an unknown, and it should be priced like one.

What does it actually deliver? Not what it's rated at. Ask how many nights they've genuinely gone unpowered, in what season, running what. "Three nights in summer, and we run the generator if it's cold" is an honest answer, and it's worth more than a spec sheet.

Then have a qualified auto electrician look at it before you hand over money on any van with a substantial system.

So what do you actually need?

The honest answer is the one the shopping lists can't give you. You need your daily watt-hours in your worst week — everything else is downstream of that number. Enough usable battery to carry the nights you'll actually do without sun. Enough charging to refill it — from solar, from the car while you drive, and from mains when you get it, because solar is one input and the alternator is the one people forget. Installed to the current standard, with the 240V done by a licensed electrician. And weighed.

A modest system you understand, sized to what you actually do, will serve you better than a spectacular one copied from someone whose trip isn't yours. The best off-grid setups aren't the biggest. They're the ones where the owner can tell you exactly why every part of it is there.

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Lithium and Solar for Australian Caravans: What You Actually Need to Stay Off-Grid