Solar Battery Bank Sizing

How it works

bank Wh = daily Wh × days of autonomy / (DoD × round-trip efficiency)
bank Ah = bank Wh / system voltage

Batteries go in series to reach the system voltage (two 12 V batteries for 24 V) and in parallel strings to reach the capacity.

Choosing the system voltage

Higher voltage means lower current for the same power, so thinner cables and smaller losses. A common rule: 12 V up to ≈ 1 kW, 24 V up to ≈ 3 kW, 48 V above.

References

• Depth of discharge — Wikipedia