Dual Battery and Lithium System Guide: Touring Power for Australian 4x4s

Modern Australian touring has moved past the old dual-battery-with-an-isolator setup. A proper touring electrical system runs 200-400Ah of lithium (LiFePO4), a DC-DC charger rated to the alternator output, 200-400W of solar, and a pure sine inverter for AC appliances. It'll run a 12V fridge for a week, charge phones and laptops for two people, and power basic AC tools — without starting the engine.

This guide covers how to design and spec a touring electrical system for an Australian 4x4 — what each component does, how to size it, and what to budget.

Lead-acid vs lithium — why lithium won

Until about 2020, dual-battery systems were almost all lead-acid (AGM or deep-cycle flooded). Lithium (specifically LiFePO4) has since taken over because:

  • Usable capacity: Lead-acid can only discharge to 50% without damage. Lithium safely discharges to 80-90%. A 100Ah lithium gives you 80-90Ah of usable power vs 50Ah on a lead-acid.
  • Weight: A 100Ah LiFePO4 is 12-14kg. An equivalent AGM is 28-30kg.
  • Charge speed: Lithium accepts charge up to 1C (100A into a 100Ah battery). Lead-acid tapers hard above 50% SOC.
  • Cycle life: 3000-5000 cycles at 80% DoD for lithium, vs 400-600 for lead-acid.

The upfront cost is 2-3x, but over an 8-year touring lifecycle lithium is cheaper per amp-hour.

Sizing the battery bank

Calculate your daily consumption:

  • 12V fridge (40L, medium setting): 30-50Ah/day.
  • LED camp lights: 5-10Ah/day.
  • Phone/laptop charging (two people): 10-15Ah/day.
  • Water pump: 2-5Ah/day.
  • Awning LED strip: 5Ah/day.

Typical two-person touring daily draw: 60-100Ah/day. You want minimum 2x your daily draw as reserve, so:

  • Weekend tourer: 100Ah lithium.
  • Extended tourer (no RTT heater): 200Ah lithium.
  • Extended tourer with inverter-heavy use: 300-400Ah lithium.
  • Expedition build with full inverter-kitchen: 400-600Ah lithium.

DC-DC charger — the heart of the system

A DC-DC charger is what moves power from your alternator to the auxiliary battery. It isolates the aux battery from the starter (so you can't flatten your crank battery), and runs a proper multi-stage charge profile regardless of alternator output voltage.

Size to match your alternator:

  • Factory alternator (120-180A) with single lithium aux: 25A DC-DC.
  • Factory alternator + 200-400Ah aux bank: 40A DC-DC.
  • Upgraded alternator (220A+) + 400Ah+ aux bank: 50-60A DC-DC.

Common brands: Redarc BCDC, Victron Orion-Tr Smart, Enerdrive ePOWER, DC4000.

Solar

Solar extends the battery's runtime when stationary. A 200-400W panel array, properly oriented, will produce:

  • Summer (full sun, northern Australia): 60-100Ah/day.
  • Winter (southern Australia): 30-50Ah/day.
  • Overcast: 10-20Ah/day.

Panel types:

  • Fixed roof panels: Permanent. Always charging when parked in sun. Best for set-and-forget builds.
  • Portable blanket panels: Fold out to angle into the sun. Most efficient per watt, but need setup.
  • Semi-flexible (curved roof): Lower efficiency but can fit irregular surfaces.

An MPPT solar controller is essential — don't use a cheap PWM controller. Look for Victron MPPT, Redarc Manager, or Enerdrive ePOWER.

Inverter — do you need one?

A pure sine inverter lets you run AC appliances (laptops, CPAP machines, kettles, power tools) from your 12V battery. Sizing:

  • 300-500W: Laptops, CPAP, phone chargers, small tools.
  • 1000-1500W: Kettle, microwave, hair dryer, medium power tools.
  • 2000-3000W: Air conditioning, full galley, serious tools.

For most touring, 1000-2000W pure sine is the sweet spot. Modified-sine inverters are cheaper but will destroy modern laptop chargers — always buy pure sine.

System layout

A properly-designed system:

  • Crank battery (factory).
  • DC-DC charger isolating crank from aux.
  • 200-400Ah lithium aux bank in canopy or under-tray.
  • MPPT solar controller with 200-400W input.
  • 1000-2000W pure sine inverter.
  • 12V distribution box with separate fused circuits for fridge, lighting, water, comms.

Lithium ventilation

LiFePO4 is safer than older chemistries but still needs ventilation in a sealed canopy. Always plan battery placement with airflow in mind. Most lithium batteries will cut themselves off at 60°C — in a closed canopy in the NT summer, that's a real concern.

Pricing — full touring electrical system

  • 100Ah LiFePO4 + 25A DC-DC + wiring: $1,200 - $1,800
  • 200Ah LiFePO4 + 40A DC-DC + MPPT + 200W solar: $2,500 - $3,800
  • 400Ah LiFePO4 + 50A DC-DC + MPPT + 300W solar + 2000W inverter: $4,500 - $6,500
  • 600Ah expedition system: $7,000 - $10,500

Professional installation: $1,200 - $2,500 depending on complexity.

Brands we stock

  • Redarc (Australian): BCDC chargers, Manager systems. Premium price, premium reliability.
  • Enerdrive (Australian): ePOWER range. Integrated systems, great for canopy builds.
  • Victron (Dutch): Orion-Tr Smart, MPPT controllers, SmartShunt. Bluetooth-managed.
  • Invicta / Itech (Australian): Lithium batteries with BMS.
  • Renogy: Value-oriented full systems.

Don't cheap out

The electrical system is where cheap parts fail and cause real problems in the desert. Buy once, cry once — $500 saved on a no-name inverter in 2026 means $5,000 of damaged gear when the inverter fries your laptop in 2027.

Why Kren Bits

We spec full touring electrical systems from Redarc, Enerdrive, Victron, and the major Australian lithium brands. Send us your vehicle, your daily Ah estimate, and your solar / inverter targets — we'll build a parts list and freight it to your door.

Browse the full range of touring electrical gear or contact us with your build.

All components ship with minimum 2-year warranty. Professional fitting available through partner workshops.

Back to blog