PureStress:
The battery has 7 amps, 20ah. Does that mean it lasts for 20 hours?
The battery claims "12volt 7Ah/20HR"
Which means total capacity is 7Ah if you discharge it over a 20hour timespan.
So if you drain it in 20hours, you project can draw 7A/20hr = 0.35A = 350mA.
If you draw 7Amps, it SHOULD last one hour, but it doesn't.
Because losses are higher at higher currents.
But..., it's a common lead/acid/gel battery, and you shouldn't drain them more than 50% if you want them to last. Batteries like that are ok for backup systems (alarms/lights/computer UPS) but not suitable for daily 100% charge/discharge.
Leo..