Formula: Battery Ah - Watts of the load multiplied by the required runtime multiplied by the DoD devided by the desired battery voltage multiplied by the efficiency of the inverter.
If you have a 100 watts 42" TV and a 12V 7ah battery lying around and a UPS for example, then you can work out the runtime using the calculator below.
| Hours | Minutes | Total Minutes |
|---|---|---|
| 1 | 0 | 60 |
| 1 | 30 | 90 |
| 2 | 0 | 120 |
| 2 | 30 | 150 |
| 3 | 0 | 180 |
| 3 | 30 | 210 |
| 4 | 0 | 240 |
| 4 | 30 | 270 |
| 5 | 0 | 300 |
| 5 | 30 | 330 |
| 6 | 0 | 360 |
| 6 | 30 | 390 |
The calculator will show you both Lithium and Lead Acid battery options.
The calculator automatically sets the optimal depth of discharge (DoD) depending on the load and battery type. To prolong the life of a battery, a lead-acid battery should not frequently be discharged below 70%, and Lithium-ion battery not below 20%. Note that 0% is a flat battery and 100% is a full battery.
If we ignore the losses during charging, divide the battery capacity by the charging current to obtain the battery's charging time in hours.
For example to charge a 100Ah Lead Acid battery using a 5Ah Optimate 6 charger will take roughly ±16 hours to recharge