100Ah vs 200Ah lithium battery for a caravan: which size?

What does 100Ah versus 200Ah actually mean?

At a nominal 12.8V, a 100Ah LiFePO4 battery stores about 1,280Wh and a 200Ah battery about 2,560Wh before the manufacturer's operating limits and system losses. These are nominal examples, not guaranteed usable capacities.

A 200Ah battery may provide roughly twice the nominal stored energy at the same voltage, but the extra capacity can increase purchase cost, weight and space requirements. Battery designs and permitted discharge currents vary by model.

Estimate your real daily use

Write down the daily watt-hours for the fridge, lighting, fans, device charging, pumps and any inverter loads. Use a fridge's measured or manufacturer-specified daily energy consumption under relevant conditions rather than multiplying its peak draw by 24 hours.

For illustration, a system using 600Wh per day would consume 1,800Wh over three days without recharging. That is more than the nominal energy in a 100Ah 12.8V battery, while a 200Ah model has more headroom before losses and reserves. Actual results depend on manufacturer limits.

Charging can matter more than capacity

If you can replenish energy daily with adequate solar, alternator charging or mains power, a smaller battery may be workable. In shade, poor weather or extended stationary camping, more storage can be useful.

A larger battery still needs appropriate charging equipment and enough time or solar input to recharge. Check battery, BMS, DC-DC charger, solar controller, fusing and cabling compatibility with a qualified installer.

How to decide

A 100Ah battery can suit modest loads and frequent charging when the energy budget supports it. A 200Ah option may be worth investigating for longer stays, multiple appliances or reduced charging opportunities.

Compare verified usable watt-hours, continuous discharge current, physical dimensions, weight, installation location, warranty and Australian support. Do not assume all batteries with the same Ah rating are interchangeable.

Before you buy: checklist

• Calculate daily Wh usage
• Decide days between reliable recharges
• Check nominal and usable battery Wh
• Compare size, weight and installation limits
• Confirm BMS discharge and charging ratings
• Allow reserve for poor weather and losses

Frequently asked questions

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