Custom dual battery systems, designed & fitted in Townsville.
From a weekend fridge setup to a full off-grid build — we match the charging, battery and wiring to how you travel, then supply or professionally fit it.
What is a dual battery system?
A dual battery system runs your fridge, lights, inverter and USB from a second (auxiliary) battery, so you never flatten the battery that starts your vehicle. The auxiliary battery is charged separately — from your alternator while you drive, from solar while you're parked, and from 240V mains when you're home or on a powered site — and an isolator or smart charger keeps the two batteries apart so your start battery is always protected.
The right system depends on three things: how much power you use each day, how you'll recharge it, and where it has to fit. This page walks through all three, then our selector and team help you land on the exact build.
The three ways it charges
Alternator (DC-DC)
A DC-DC charger tops up the second battery while you drive and correctly charges lithium in stages. 25A suits a weekend fridge; 50A recharges bigger lithium banks in a couple of hours' driving and suits smart-alternator vehicles.
Solar (MPPT)
Solar keeps you charged while parked. A built-in MPPT regulator draws maximum power even in low light. As a guide, 200W of solar replaces roughly 60–80Ah on a good day — enough to run a fridge indefinitely when you're camped.
240V Mains
A mains charger tops the bank up fast at home or on a powered site — ideal for caravans and vans between trips. On bigger builds an inverter/charger such as a Victron MultiPlus does both 240V charging and 240V output in one unit.
How much battery do you need?
Size your lithium bank to your daily power use (in amp-hours) multiplied by how many days you want off-grid before a recharge. The fridge is the biggest everyday draw; on a caravan or full off-grid van the 240V appliances add up fast — aircon and induction especially.
Everyday 12V loads
| Appliance | Typical use |
|---|---|
| 12V fridge (40L) | ~45 Ah/day |
| 12V fridge/freezer (85L) | ~80 Ah/day |
| LED lights | ~10 Ah/day |
| Water pump | ~5 Ah/day |
| Diesel heater | ~15 Ah/day |
| Roof fan (Maxxair) | ~15 Ah/day |
| Phone & tablet charging | ~10 Ah/day |
| Starlink | ~20 Ah/day |
| CPAP machine | ~40 Ah/night |
| 12V TV | ~8 Ah/hr |
Caravan & off-grid appliances (240V via inverter)
| Appliance | Typical use |
|---|---|
| Laptop | ~20 Ah/day |
| Toaster | ~8 Ah/use |
| Coffee machine | ~30 Ah/use |
| Microwave | ~20 Ah/use |
| Air fryer | ~25 Ah/use |
| Hair dryer | ~20 Ah/use |
| Induction cooktop | ~40 Ah/meal |
| Washing machine | ~45 Ah/cycle |
| Air conditioner | ~90 Ah/hr |
| Electric water heater | heavy — quoted per build |
How much solar do you need?
Solar recharges your battery while you're parked. Match it to your daily use so you replace what you draw on an average day. These figures are a guide for good northern-Australia sun — the big off-grid vans (the full-time “live in a van” builds) typically run 600–1200W paired with 400–628Ah of lithium.
| Solar array | Typical daily charge |
|---|---|
| 200W | ~60–80 Ah/day |
| 400W | ~120–160 Ah/day |
| 600W | ~180–240 Ah/day |
| 800W | ~240–320 Ah/day |
| 1000W+ | ~300–400 Ah/day |
An MPPT regulator (built into our systems) draws maximum power from every panel, even in low light. Add a bit more solar than the maths suggests to cover cloudy days.
Lithium vs AGM
Lithium (LiFePO4) is the standard for modern touring — lighter, longer-lasting, and you can use almost all of its capacity. AGM still suits budget or occasional setups.
| ATG Lithium (LiFePO4) | AGM | |
|---|---|---|
| Usable capacity | ~100% | ~50% |
| Weight | Light | Heavy (2–3x) |
| Cycle life | 2000–4000+ | 300–500 |
| Charge speed | Fast | Slower |
| Upfront cost | Higher | Lower |
| Cost per usable cycle | Lower | Higher |
| Best for | Touring & off-grid | Budget & occasional |
What's in a complete system
A well-built system is more than a battery. These are the parts we design together so everything charges correctly and safely.
Wiring diagrams
From a simple in-vehicle build to a complete off-grid van. Every job is wired, individually fused and labelled to suit your vehicle.
Full off-grid van: solar and alternator charge the lithium bank; the MultiPlus-II charges from 240V shore power and inverts battery power to run aircon, induction and appliances. Every circuit is individually fused.
What suits your rig
Ute canopy or tray
A wall-mounted Control Hub or pre-wired panel with a slimline lithium battery keeps everything tidy behind the drawers. DC-DC + solar covers most trips; add an inverter for tools and appliances.
Wagon or 4WD
A behind-seat or cargo-area lithium battery with a 50A DC-DC and a solar input. Compact, hidden, and plenty for a fridge, lights and a small inverter.
Caravan or camper
Bigger lithium bank with a Manager or MultiPlus for DC, solar and 240V charging, roof solar, and an inverter for full 240V living on site.
Van or full off-grid
Maximum lithium (400–628Ah), 600–1200W of solar and a MultiPlus-II inverter/charger to run aircon and induction — designed and commissioned as one complete system.
Dual battery selector
Answer three quick questions and we'll suggest a starting point.
Our install process
Tell us your vehicle and what you want to run. We talk through how you travel.
We size the battery, charging and wiring to your power use and space.
Genuine REDARC, Enerdrive, Victron or Hardkorr gear, matched with ATG lithium.
Professional install — correctly fused, labelled and tidy, done in Townsville.
We test every circuit and show you the monitoring app before you drive away.
Recent installs
A few dual battery systems we've designed and fitted for local customers — read the full write-ups.
Dual battery FAQs
Should I choose lithium or AGM?
For most touring and off-grid setups, lithium (LiFePO4) is the better choice — it is far lighter, lasts several times longer and lets you use nearly all of its capacity. AGM still suits budget builds or occasional use.
How much battery capacity do I need?
A weekend fridge and lights suits 100 to 120Ah, touring with a small inverter suits 150 to 210Ah, extended off-grid caravans suit 300Ah+, and full off-grid vans running aircon and induction want 400 to 628Ah. Our selector above will suggest a size.
How much solar should I add?
Match solar to your daily use: roughly 200W replaces 60 to 80Ah a day. Weekend setups suit 200 to 400W, caravans 400 to 600W, and full off-grid vans 600 to 1200W paired with 400 to 628Ah of lithium.
How long does a professional install take?
Most in-vehicle dual battery installs take half a day to a full day. Full caravan and off-grid van builds can take one to three days depending on solar, 240V and cabinetry.
Can I run an air conditioner or induction cooktop?
Yes, with a large enough lithium bank, a suitable inverter and plenty of solar. These loads are heavy, so we size the system carefully — typically 400Ah or more with 600W+ of solar and a MultiPlus-II inverter/charger.
Can you upgrade my existing setup?
Yes. We can add solar, a bigger DC-DC charger, an inverter or swap AGM for lithium, and re-use suitable existing components where it makes sense.
What warranty comes with the system?
Every component carries its manufacturer warranty (typically 2 to 5 years), and our workmanship is guaranteed. ATG lithium batteries include their own warranty and Bluetooth monitoring.
Ready to build your system?
Tell us your vehicle and what you want to run — we'll design the right dual battery system and give you a fixed quote, supplied or fitted.