What size 12V battery, solar and DC-DC charger do you need?
Add the fridge and gear you actually use. AMP'D will estimate your daily amp-hours and recommend battery, solar, DC-DC charger and inverter sizes for your 4WD, camper or caravan.
12V system sizing guide
What this 12V calculator works out
Battery capacity from your real daily use
Start by adding the equipment you actually take camping: your 12V fridge, lights, water pump, phones, Starlink, CPAP and any 240V appliances used through an inverter. The calculator converts those loads into an estimated daily amp-hour figure, then allows for your chosen days of autonomy and battery chemistry. Lithium and AGM batteries are treated differently because they do not provide the same practical usable capacity.
Solar sized for Australian touring conditions
Solar output is not based on the panel's sticker wattage alone. Season, shade, mounting style and whether you use an MPPT or PWM controller all affect the energy that reaches your battery. The result deliberately uses realistic system losses so a nominal 200W panel is not treated as though it produces 200W continuously throughout the day.
DC-DC charger sizing from driving time
A larger charger is not automatically better. AMP'D 12V compares the energy you use with the number of hours you normally drive and recommends a practical DC-DC charger size. Your alternator capacity, charger input limits, battery BMS, cable run and manufacturer instructions still need to be checked before buying or installing equipment.
Inverter size and peak battery demand
Inverters are sized from peak watts, while battery capacity is based mainly on energy used over time. A coffee machine or induction cooker may run briefly but still demand very high current. The calculator checks the largest selected load and highlights when the inverter, battery discharge rating or BMS may need closer attention.
How to use your result
Treat the recommendation as a planning starting point rather than an installation specification. Real consumption changes with temperature, appliance model, fridge ventilation, battery age and user behaviour. Check the result against the exact specifications of the products you are considering, including maximum charge and discharge current, and have cabling, fusing and installation requirements confirmed by a suitably qualified person.
Can I use this as a 12V fridge power consumption calculator?
Yes. Select the closest fridge size and add freezer mode for harder use. The calculator combines the fridge estimate with your other loads so the battery and charging result reflects the whole setup rather than the fridge alone.