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How many watts are required

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Member level 3
Oct 5, 2012
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Salam Every One

I want to develop a solar system in which i am using a battery of 12V 40AH and i want to run a fan of 12V 2A.
I need a solar pannel which not only charge the battery in a complete day but also run the fan simultaneously.
Mean if i run the fan in the morning, the solar pannel should not only run it till evening but also it should charge my battery fully till evening
Now how many Waats of solar pannel are required to do so.
I am from Pakistan and living at spatial position 74N 31E. Position is mentioned here only to tell that here it is hot summers and sun glooms 14h hours normally.

Also please guied how to calculte the waats of solar pannel according to fulfill the capasity of load


your minimum requirement is (12*2*24 plus loss)/14 you can take a solar panel of higher VA than this

hi smhn72
your battery is rated at 12v 40ah, so if u use a constant current charger to charge your battery , u need to give battery (AH/10)amp i.e. 40/10= 4ampere, now u also have to apply 14.1 volts to battery terminal so your power required to charge the battery is 14.1*4 = 56.4watts. and also u hve to run a fan simultaneously of 12v 2amp so power consumed by the fan is 12*2= 24watts, so total power is 24+56.4=80.4 watts , so u can buy a pannel greater than 80.4watts .
Hi BaWA,
Your calculation is better than mine, I learned something from you Thanks

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