Well, that depends on what you are going to use it for and for how long
Need to consider
- The potential load in WattHours
- The efficiency of the devices on the circuit (for example the invertor)
- The recommended maximum depth of discharge of the battery
To calculate the potential load
List all the devices and how long they would be used for
e.g.
Charging iPad – 3 hours
Charging phone – 2 hours
Water pump – 15 minutes
LED Lights – 8 hours
| Power consumption (Watts) | Time (Hours) | Load (WattHours) |
|
|---|---|---|---|
| Charging tablet | 10.5 | 1 | 10.5 |
| Charging Surface Pro | 33.8 | 2 | 67.6 |
| Charging mobile phone | 5.8 | 1 | 5.8 |
| Charging mobile battery pack | 0 | ||
| Charging torch | 6 | 1 | 6 |
| Charging bike lights | 0 | ||
| Charging drone batteries | 0 | ||
| Charging camera battery | 0 | ||
| Charging GPS Watch | 0.8 | 1 | 0.8 |
| Water pump | 6 | 0.25 | 1.5 |
| Total WattHours (WH): 92.2 | |||
| Total AmpHours (AH): 7.68 |
To calculate the AmpHours (Ah) needed, divide the WattHours (Wh) by the voltage (V)
Wh/V = Ah
33.7/12 = 7.08