7.2w led panel with 12v 7Ah battery

[arecssor]

Hi ,

i am trying to power a led panel of 7.2W (12V, 600mA) and a controller board with atmega8 microcontroller i want t run this circuit and light up the led panel for 4-5 hrs is that possible to achieve this running hours with 12v 7,Ah battery .to achieve this what is the battery capacity that i should select ,now am connecting the led through a 7812 regulator ic it is not working properly .
and i have another panel of 3W(6v,500mA) if i replace the 7.2W led panel with this 3W panel how much additional running hours can be achieved with the same 12v 7Ah battery .

 

[Easyrider83]

7812 have ~2V minimum voltage drop. That's why I doesn't work. Even if you will use LDO, this solution will be poor.
You need to clarify more details about your panel. How strictly it needs 12V? In this case SEPIC DC-DC converter have to be used, but this solution is expensive and efficency will be poor also (60-70%).
May be direct connection will be most optimal way.

 

[KlausST]

Hi,

Please don´t post very similar threads.
Currently I consider if I should merge both threads.

****
Generally:
Power = V x I (in Watts)
Energy = P x t = V x I x t (in Ws, Wh or kWh)

Energy in a battery: V x I x t (Where I x t is already given in Ah) therefore: 12V x 7Ah = 84Wh

Now you have a panel of 7.2W. Just divide the energy of the battery with the power of the LED and get the time: 84Wh / 7.2W = 11.7h

This is with 100% full to 0% empty new batteries with 100% efficiency.
Calculate with 80% of battery energy. --> gives about 9h

What efficiency you have to calculate with depends on YOUR circuit.
Expect about 50% form a linear circuit (other 50% = loss = heat)
Expect 80...95% (or more) from a switching solution.

Klaus