Proper Selection of a Solar Panel to Match Load

[smhn72@gmail.com]

Dear SIR
I have a 12v, 20 Ah DC load and i want to purchase a solar pannel to run this load. Please guied me how much watts of solar pannel are required to run this load

 

[FoxyRick]

20Ah is a battery capacity, not a load.

Do you want to charge a 12V, 20Ah battery? If so, what is the purpose of the battery, what will it power, how much current will be required over what time periods, and what is the environment (how much sunlight daily etc)?

 

[smhn72@gmail.com]

I have FIVE 12v 2ah DC fans and five lights of same capasity
whom i want to run and also a battry of 60ah to b charged simultanously.
now how many watts of pannel are required???????????????????????????

 

[ragav4456]

U need 300 watts solar panel.
panel output=12v and 10Amps

 

[bigdogguru]

Please guide us with a better choice of title next time.

As the following title has little to nothing to do with the topic of thread.

Please guied me as soon as possilble

Thread title changed.

BigDog

 

[FoxyRick]

Please don't so things like this: "required???????????????????????????". One "?" will do. Thank you.

Again, Ah is used as a battery capacity, not a measure of current or load. So, you cannot have a 2Ah fan or light. I take it you mean a 2A fan or light.

So, you have a total current requirement of 5x2 (for lights) + 5x2 (for fans) = 20A. Is the battery intended to run the fans and lights? If so, note that your battery (60Ah) will only run this for three hours.

If you want to charge the battery quickly, you must use a charge controller and large photovoltaic panel. Ideally, a MPPT charge controller because that will get the most out of your panel.

Now, let's say that you have eight hours of full sunlight, and need to charge the battery from empty to full in one day. The battery would need (60/8)=7.5A , but charging is not efficient so let's call that 10A for eight hours.

Your total, maximum current requirement is now 30A, or 360W. Using an MPPT controller, you might get away with a 500W panel. Assuming that you have suitable weather...

Without more detailed information from you, that's my best guess.

 

[knikhil271083]

@FoxyRick: Nice deductions. I agree.

@smhn72@gmail.com: You can go through this application note from Linear.

"http://cds.linear.com/docs/LT%20Journal/LTMag-V19N4-04-LT3652-JimDrew.pdf"

It specifies design of a solar cell battery charger when used with LT3652. Using an MPPT device is recommended.

 

[smhn72@gmail.com]

Thanks u Sir
u guied me in a best way
Sir i hav a battery of 12v 7ah and a load of 12v 2A
plz guied me the backup time of battery

 

[FoxyRick]

Battery capacities are given assuming a certain current draw, usually to give the highest Ah number they can get. So you would need to check your battery datasheet (or ask the supplier) for the exact Ah rating for a 2A current drain. The more current you draw, the less effective capacity you will get from the battery.

Simply though, 7Ah / 2A = 3.5 hours.

Likely you will get less than that due to what I said above. Also, that is to full exhaustion, which is really not a good idea to do because it can reduce the expected life time of the battery. Better to stop and recharge before the battery is completely exhausted.