Getting a HiAce camper solar setup right the first time

A HiAce camper solar setup usually fails for one reason. It was sized by guesswork. REDARC’s worked example puts a typical camper at 67 amp-hours a day, with the fridge taking 56 of them. Everything else follows from that number.

How much power does a HiAce camper use in a day?

A typical camper draws about 67 amp-hours of 12V power in 24 hours, based on a worked example from REDARC Electronics covering a 35-litre fridge, LED lighting, a portable stereo and phone charging. An amp-hour is the amount of current a battery can supply for one hour, and it’s the unit every other decision in the build gets sized against.

The method is arithmetic, not engineering. REDARC’s approach is to multiply each appliance’s current draw in amps by the hours it runs in a day, then add the results together. Its figures for the common loads:

• Fridge: 56Ah a day, or roughly 84% of the total in that example.
• 12V LED light: 0.5A, so four hours of lighting costs 2Ah.
• Phone charger: 2A, or 4Ah over a two-hour charge.

Two things fall out of this. The fridge is the system and everything else is rounding, so a more efficient fridge does more for you than a bigger battery. And if your build adds a diesel heater, a 12V water pump or an inverter for a laptop, your number isn’t the same as anyone else’s. Run the arithmetic off your own appliance labels rather than borrowing someone else’s total.

How big should the battery bank be?

If you’re running AGM, the bank has to be at least double your daily draw, because REDARC advises discharging a deep cycle lead-acid or AGM battery no more than 50 per cent. At 67Ah a day that’s a 134Ah minimum for a single night. Depth of discharge, the share of a battery’s rated capacity you actually take out before recharging, is what separates a bank that lasts years from one that’s tired in a season.

Lithium changes the arithmetic rather than the principle. Enerdrive rates its B-TEC 12V 100Ah battery at 2,000 or more cycles at 80 per cent depth of discharge, so 80 of those 100 amp-hours are genuinely usable. One day of autonomy needs about 134Ah of AGM or roughly 84Ah of lithium.

Now scale it to three days with no useful sun. That’s around 400Ah of AGM, and at 37.8 kilograms per 120Ah battery you’re carrying more than 113kg of lead in a van that also has to hold water, food and a bed. There’s a ceiling on the lithium side too. Enerdrive allows a maximum of two B-TEC units in parallel, which caps that particular battery at 200Ah. Most HiAce builds land between 100Ah and 200Ah of lithium and cover the gap with charging rather than storage.

Is lithium worth five times the price of AGM?

In a HiAce, usually yes, and the reason is weight rather than performance. Jaycar lists a 12V 120Ah AGM deep cycle battery at $239 and 37.8kg, while 4×4 Industries lists the Enerdrive ePower B-TEC 100Ah slimline lithium at $1,275, discounted from $1,612, at 12.4kg. That’s about $1,036 more for a battery that saves 25kg.

Shape matters as much as mass. The Enerdrive slimline measures 551 x 101 x 239mm, narrow enough to sit behind a seat or under a bed platform where a 120Ah AGM would eat a storage locker. It carries a 5-year warranty and an internal battery management system that protects against overcharge, over-discharge, over-temperature and short circuits, per Enerdrive’s product listing. AGM has none of that, so how deeply you discharge it is on you.

Here’s how the two compare on the figures that matter, using Jaycar’s AGM listing and 4×4 Industries’ price for the Enerdrive lithium.

Battery	Price	Weight	Rated capacity	Usable capacity	Cost per usable Ah
Jaycar 12V 120Ah AGM deep cycle battery	$239	37.8kg	120Ah	60Ah at 50% DoD	$3.98
Enerdrive ePower B-TEC 100Ah slimline lithium	$1,275	12.4kg	100Ah	80Ah at 80% DoD	$15.94

Read that last column honestly. AGM is far cheaper per amp-hour you can actually use, and if weight and space are no object it’s a defensible choice. What you’re buying with lithium is weight back on a payload you’re probably already close to, a shape that fits where lead won’t, and the cycle life Enerdrive quotes instead of a battery you replace. Best for builds carrying a fridge, water and gear in a van near its weight limit, lithium wins on the numbers that constrain a HiAce.

How many watts of solar do you actually need?

Multiply your daily amp-hours by 12 to get watt-hours, divide by the six hours of good sun REDARC assumes, then add at least 20 per cent for weather, shade and system losses. For the 67Ah camper that’s 804 watt-hours, 134W of panel, and 161W once the margin is added, which is precisely the step REDARC’s own example takes.

So a single 200W panel covers a fridge-plus-lights build with room to spare, and REDARC’s guidance is that 150W is enough to keep a modern 12V fridge running 24 hours a day. The temptation is to double it anyway. Resist that until you’ve measured your loads, because roof space on a HiAce is finite and a second panel that spends half the trip shaded by a pop-top or a roof rack earns nothing.

Why does the fridge die on the third day off-grid?

Because the system was sized for six hours of sun and then handed three days that didn’t deliver it. The fridge keeps pulling its 56 amp-hours a day whatever the weather, so a small daily shortfall compounds. Lose a third of your input and you’re roughly 20Ah down each day, which a bank holding one day of usable capacity absorbs once and not twice. These are the mistakes that get people there, drawing on the Enerdrive specifications and REDARC’s sizing margins:

• Sizing panels on the sunny-day figure without REDARC’s 20 per cent margin.
• Leaving the van parked in shade all day because it’s cooler inside.
• Starting the trip with a bank that was never fully charged at home.
• Running an inverter beyond the 1000W maximum a single B-TEC 100Ah battery is rated for.
• Planning to add batteries later, when the Enerdrive limit is two units in parallel.

The fix that actually holds is a DC-DC charger, a unit that takes power from the alternator while you drive and feeds it into the house battery at the correct voltage. It doesn’t care about cloud, and half an hour of driving between campsites puts back what a grey morning cost you. Solar handles the days you stay put, the alternator handles the days you move, and the battery bank only has to bridge the gap between them.

Do the arithmetic once, on your own appliances. Size the bank at double your daily draw for AGM, or a little above it for lithium, then size the panels using REDARC’s method of daily watt-hours divided by six hours of sun plus a 20 per cent margin. Fit a DC-DC charger so a bad run of weather is an inconvenience rather than a spoiled fridge full of food.