RV, marine, solar off-grid and home backup have different load shapes. Pick the application, then size the bank around a real day — not a headline capacity.
Each page follows the same structure: typical loads → how to size → which model → install notes.
Size the bank around a real day of use: the fridge cycles all night, the inverter pulls a surge at breakfast, and the alternator only charges while you drive.
Open the guideMarine loads are bursty: a trolling motor pulls hard for hours, a bilge pump kicks in without warning, and everything lives in a damp, vibrating space.
Open the guideOff-grid sizing is a loop: daily load decides the bank, the bank decides the array, and the array has to refill the bank on the worst realistic day.
Open the guideBackup is not whole-home storage by default. Pick the critical circuits first — sump pump, fridge, lights, internet, medical equipment — then size the battery and inverter.
Open the guideDaily energy in Wh, and the system voltage. Once those are fixed, the model and parallel count follow.
List every load as watts × hours per day. Add 30% for inverter losses and ageing. Then divide by voltage and 80% depth of discharge.
Wh/day × days ÷ (0.8 × 0.85) ÷ V = Ah
0.8 = usable depth of discharge; 0.85 = inverter efficiency. Round up to the next model or parallel count.
Application, daily runtime, inverter size and destination market are enough for a first recommendation.