# Solar system calculator

3 Posts
Jan 14, 2009 01:47 pm
Solar system calculator

Hello
I have some questions.
Firstly what is the difference between off-grid and on-grid for the calculator?

secondly for the battery bank secion of the off grid calculator i have some trouble understanding it. In the results section it says this:

line1: Battery bank capacity: 9,853 watt hours
line2: Select a battery bank voltage:
line3: For a battery bank voltage of 12 volts
line4: Battery Bank capacity: 821 amp hours
line5: 3 string configuration: 274 amp hours per string

Where does it get the details in line4, 821 amp hours?
In line5 what does 3 string mean? is it the amount of batteries?

Thanks

578 Posts
Jan 14, 2009 02:02 pm
Re: Solar system calculator

the difference is that one has batteries and the other does not.  so the total system inefficiencies are greater when batteries are involved.

in line 4 that would be the amp hour rating for the battery bank at the voltage that was selected.

in 3 strings means that ideally you should have 3 series strings of batteries or fewer so as to limit connections and potential for unequal charging and discharging.  so in your example it is saying that if you needed an 821ah bank @12v, you would need each series string to have 274 ah for each of its 3 strings.

james
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3 Posts
Jan 14, 2009 02:08 pm
Re: Solar system calculator

so the 3 means three batteries? each of 274?

351 Posts
Jan 14, 2009 02:30 pm
Re: Solar system calculator

If you are using 12V batteries that are 274Ah or greater yes.
But if you are using 6V batteries, each string would be two batteries, for a total of 6.
If you were using 2V batteries, you would have 18.

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