Solar Charger Formula Question

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doonot
 
Posts: 3
Joined: Thu Aug 25, 2011 5:02 am

Solar Charger Formula Question

Post by doonot »

Hi
I already built an iPhone Solar Charger and I try to optimize it now with different components. I once found this formula on your page:

(Battery milliAmphour capacity) / minimum (solar panel current output, charger maximum output) * 1.20 (inefficiencies) = Hours

So let's say I have a :
- solar pannel that has an output of 6V at 530 mA.
- battery with 3.7V 6600mAh

Question 1: Does that mean it takes 6600/530 * 1.20 = approx. 15 hours to load the battery (of course with full sun)?
Question 2: You specified a cell efficency of 17%+ for the solar panel, why do you then multiply it with 1.20, and not divide it through 0.17?
Question 3: Is there a way to find out the mAh number if you know that the solar panel has an output of 6V and 5W?

Thanks a lot for the answer, I much appreciate it.

Best regards,
doonot

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: Solar Charger Formula Question

Post by adafruit »

1. yes
2. its already calculated in the solar panel rating
3. 5W/6V = Amps

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