Q. re: ratings for short circuit and open circuit
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Posted by Kris Krieger on July 22, 2008, 1:18 pm
Please log in for more thread options I've been looking into buying solar cells, and I see a lot of this sort of description: "Square polycrystalline silicon solar cell has an output of .42V to .52V (open circuit) and a current of >1.2amp (short circuit)."
What I'm wondering is, which one translates into how much the cell will produce when it's all connected up in something like a light or motor or so on? I'd assume that'd be "closed circuit", but better to ask and know, than to assume. Thanks in advance! - Kris | |||||||||||||
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Posted by Tom Biasi on July 22, 2008, 1:44 pm
Please log in for more thread options > Well, this is sci.electronics.basics, so I have another basic question ;)
> > I've been looking into buying solar cells, and I see a lot of this sort of > description: > > "Square polycrystalline silicon solar cell has an output of .42V to .52V > (open circuit) and a current of >1.2amp (short circuit)." > > What I'm wondering is, which one translates into how much the cell will > produce when it's all connected up in something like a light or motor or > so > on? I'd assume that'd be "closed circuit", but better to ask and know, > than to assume. > > Thanks in advance! > > - Kris When you hook something up to it that's called loading it. The specs you quote indicate the maximum the cell can supply. If your load uses the spec voltage and draws less than the spec current you are loading within spec of that device. Tom | |||||||||||||
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Posted by Kris Krieger on July 22, 2008, 3:25 pm
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>
>> Well, this is sci.electronics.basics, so I have another basic
>> question ;) >> >> I've been looking into buying solar cells, and I see a lot of this >> sort of description: >> >> "Square polycrystalline silicon solar cell has an output of .42V to >> .52V (open circuit) and a current of >1.2amp (short circuit)." >> >> What I'm wondering is, which one translates into how much the cell >> will produce when it's all connected up in something like a light or >> motor or so >> on? I'd assume that'd be "closed circuit", but better to ask and >> know, than to assume. >> >> Thanks in advance! >> >> - Kris >
> When you hook something up to it that's called loading it. > The specs you quote indicate the maximum the cell can supply. > If your load uses the spec voltage and draws less than the spec > current you are loading within spec of that device. > > Tom > OK, that makes sense - so the maximum voltage a cell can deliver (in perfect sunshine) is X volts at a current (flow) of Y amps per hour. Hmmm, so why do they specify (open circuit) and (short circuit)? I did read these: http://www.answers.com/topic/short-circuit http://en.wikipedia.org/wiki/Short_circuit but I still wonder why they can't just say "max current is Y amps" - are they simply trying to indicate that, when they tested the item, it was only connected back to itself, without any intervening components that might add resistance, etc., that'd give the meter an incorrect reading? ((THe down- to-bare-earth version of that last question being, Can I just ignore (open circuit) and (short circuit) <g!>))
Thanks again! - Kris | |||||||||||||
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Posted by Tom Biasi on July 22, 2008, 3:42 pm
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>
>>
>>> Well, this is sci.electronics.basics, so I have another basic
>>> question ;) >>> >>> I've been looking into buying solar cells, and I see a lot of this >>> sort of description: >>> >>> "Square polycrystalline silicon solar cell has an output of .42V to >>> .52V (open circuit) and a current of >1.2amp (short circuit)." >>> >>> What I'm wondering is, which one translates into how much the cell >>> will produce when it's all connected up in something like a light or >>> motor or so >>> on? I'd assume that'd be "closed circuit", but better to ask and >>> know, than to assume. >>> >>> Thanks in advance! >>> >>> - Kris >>
>> When you hook something up to it that's called loading it. >> The specs you quote indicate the maximum the cell can supply. >> If your load uses the spec voltage and draws less than the spec >> current you are loading within spec of that device. >> >> Tom >> >
Sure you can just ignore it but its the info that you need.
> OK, that makes sense - so the maximum voltage a cell can deliver (in > perfect sunshine) is X volts at a current (flow) of Y amps per hour. > > Hmmm, so why do they specify (open circuit) and (short circuit)? I did > read these: > http://www.answers.com/topic/short-circuit > http://en.wikipedia.org/wiki/Short_circuit > but I still wonder why they can't just say "max current is Y amps" - are > they simply trying to indicate that, when they tested the item, it was > only > connected back to itself, without any intervening components that might > add > resistance, etc., that'd give the meter an incorrect reading? ((THe down- > to-bare-earth version of that last question being, Can I just ignore (open > circuit) and (short circuit) <g!>)) > > Thanks again! > > - Kris When they specify open circuit voltage its saying that the device cannot deliver more than that. When you load it you will get less. The device has internal resistance. The internal resistance effects the maximum current that can be supplied. With a short circuit (zero ohm load) the internal resistance is such that the device cannot supply more current than specified. Less than a short you can expect less voltage than open circuit and less current than shot circuit. Tom | |||||||||||||
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Posted by Kris Krieger on July 22, 2008, 4:39 pm
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>
>>
>>>
>>>> Well, this is sci.electronics.basics, so I have another basic >>>> question ;) >>>> >>>> I've been looking into buying solar cells, and I see a lot of this >>>> sort of description: >>>> >>>> "Square polycrystalline silicon solar cell has an output of .42V to >>>> .52V (open circuit) and a current of >1.2amp (short circuit)." >>>> >>>> What I'm wondering is, which one translates into how much the cell >>>> will produce when it's all connected up in something like a light >>>> or motor or so >>>> on? I'd assume that'd be "closed circuit", but better to ask and >>>> know, than to assume. >>>> >>>> Thanks in advance! >>>> >>>> - Kris >>> >>> When you hook something up to it that's called loading it. >>> The specs you quote indicate the maximum the cell can supply. >>> If your load uses the spec voltage and draws less than the spec >>> current you are loading within spec of that device. >>> >>> Tom >>> >>
>> OK, that makes sense - so the maximum voltage a cell can deliver (in >> perfect sunshine) is X volts at a current (flow) of Y amps per hour. >> >> Hmmm, so why do they specify (open circuit) and (short circuit)? I >> did read these: >> http://www.answers.com/topic/short-circuit >> http://en.wikipedia.org/wiki/Short_circuit >> but I still wonder why they can't just say "max current is Y amps" - >> are they simply trying to indicate that, when they tested the item, >> it was only >> connected back to itself, without any intervening components that >> might add >> resistance, etc., that'd give the meter an incorrect reading? ((THe >> down- to-bare-earth version of that last question being, Can I just >> ignore (open circuit) and (short circuit) <g!>)) >> >> Thanks again! >> >> - Kris > Sure you can just ignore it but its the info that you need.
> When they specify open circuit voltage its saying that the device > cannot deliver more than that. When you load it you will get less. > The device has internal resistance. The internal resistance effects > the maximum current that can be supplied. With a short circuit (zero > ohm load) the internal resistance is such that the device cannot > supply more current than specified. Less than a short you can expect > less voltage than open circuit and less current than short circuit. > > Tom Oh! OK, great, thank you! I wrote that into my Notebook :) - Kris | |||||||||||||
