# Solar Power Questions



## NotsoGreyman (Nov 16, 2016)

Question. For reasons I will later explain, I think I figured out this bit of Solar Power MumboJumbo.

Lets say I bought a 15w/12 solar panel

Then Ran it to a charge controller 

Using these Items to charge a 12v/35a Battery

I could then run a 200w inverter to convert to AC power 

If I have all this figured out, which im not 100% sure I have, Hence the thread. 

The battery would produce 420watts at 100% discharge. Assuming I didn't want to drain the battery below 50% that would be 210Watts. 
Lets say I wanted to run a Small TV and Bluray player off of this setup. 

If i did my math right, the TV would use 29 Watts / Hr & the Bluray 30 watts / Hr

210w/59w=3.5Hrs to 50% usage. 

Then the panel would need about 14 Hours (Peak light conditions) to return to 100% charge?


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## Targetshooter (Dec 4, 2015)

Did you use a wattage calculator ? or voltage ?


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## NotsoGreyman (Nov 16, 2016)

The formula I used is VoltsxAmps=Watts to determine battery capacity. 

to determine Consumption I converted KWh to Watts. Just using the Google calculator of 0.029 and 0.030


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## azrancher (Dec 14, 2014)

NotsoGreyman said:


> I could then run a 200w inverter to convert to DC power


Change this to read AC power.

*Rancher*


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## NotsoGreyman (Nov 16, 2016)

azrancher said:


> Change this to read AC power.
> 
> *Rancher*


Ahhh. Okay, So I'm good with a setup like that?


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## paraquack (Mar 1, 2013)

Your basic math seems close enough for government work. Depending on inverter, it can use up to 10% 
of the inverter's rating for itself. 
Based on my RV experiences (my last set of batteries lasted 11 years in my motorhome and were at 50% .
I used only a deep cycle battery, like a golf cart battery, but you need 2 batteries because 
they are only 6 volts each. The last ones I saw at Costco were $80 each. 
They are usually rated about 447 min. @ 25 amps or 115 min. @ 75 amps, Amp-Hours (AH) for a 225 AH @ 
20 hr. rated battery. Cycle Life is advertised as 750 cycles.
So they are designed to charge/discharge 750 times. Deep cycle batteries are designed to be discharged 
deeply and then recharged. So having them connected to a solar system constantly could adversely affect their
cycle life. I had 2 sets of batteries and would only charge a set as the required it, while I switched to the second
set for use. So your TV/Blueray combo could ran for maybe 40 hours +. 
So now that I gave you all sorts of info that you didn't ask about, I still say your math seems ok.


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## 8301 (Nov 29, 2014)

NotSoGreyMan, You've got the math correct except for the battery recharge time. Your battery recharge time from 50% to 100% SOC would take about 17.9hrs. There are several reasons for the longer recharge time such as panels usually don't quite reach claimed output and batteries,, especially when over 90% SOC (state of charge) have internal resistance to charging plus charge controllers loose about 2% of the energy. To keep things simple most solar professionals figure that after all these things a realistic number for power absorbed by the battery is 77% of the panel's rated output. 

Still, Your system would give you some renewable power which would be very handy to have if the power went out.


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