Size energy storage around daily consumption. Check peak power separately: a battery with enough energy may still be unable to run a demanding appliance.
Watts (W) describe how much power an appliance uses at a moment in time. Watt-hours (Wh) describe the energy used over a period. A 20 W fan running for six hours uses 120 Wh.
For a DC circuit, power is voltage multiplied by current: W = V × A. Nominal battery energy is approximately V × Ah. Amp-hours alone cannot compare batteries with different voltages.
An inverter converts battery DC into AC. A charger replenishes the battery using a compatible charging profile. Whether shore power supplies particular sockets or charges the battery depends on the installed wiring.
List the equipment you actually expect to use, its power demand and its daily operating time. For cycling appliances such as a refrigerator, use measured or applicable daily energy data rather than assuming continuous rated power.
Illustrative total: 687 Wh/day. These figures represent assumed battery-side energy, including relevant conversion losses. They are not Ecocampor product specifications.
Suppose a 12.8 V, 100 Ah battery has an 80% usable-energy allowance for this calculation. Estimated available energy is 12.8 × 100 × 0.80 = 1,024 Wh.
With no recharging, 1,024 ÷ 687 gives approximately 1.49 days. Actual usable energy and operating time depend on the battery, temperature, condition, settings and loads.
Adding a 1,000 W AC appliance for half an hour through an assumed 90% efficient inverter requires about 556 Wh from the battery. The daily total rises to about 1,243 Wh, reducing the same estimate to 0.82 days.
Energy capacity is only one check. Compare the appliance’s continuous demand and starting surge with the inverter rating, battery discharge limit and BMS limits. Cables, protection devices and connections must also suit the complete system.
Ask for the battery voltage and model, inverter continuous and surge ratings, appliance input data and a circuit description. Electrical installation and protection sizing should follow the equipment manuals and be checked by a qualified installer.
These guides explain general principles. Equipment, ratings and procedures vary by model and configuration. Use the documentation supplied with your vehicle and installed components for model-specific decisions.
