Thread: Solar panel Amps

The 200w panel puts out more power than the 130 - this is the difference. I do not follow your comment about both putting out 5A - why is this a magic number? Whether the extra power from a larger panel is worth the cost, space and weight depends on what you are using it for. Or are you asking about whether to make up the same total power from larger or smaller panel? More information needed!

John

Originally Posted by Pedro_The_Swift

Is there any advantage in going to a 200w panel over a 130 if they both put out over 5A?(infact the 130 puts out nearly 6)
Its going on the van roof so size is no problem,, but one weighs 10kgs more,,

For them to both to put out 5A or so, the 200w will be putting out a higher voltage. 5A x 40volts = 200w. 5A x 26volts = 130w.

Sent from my Galaxy Nexus using Tapatalk 2

If you mean you only need 5 amps then I guess it depends on if you need reserve capacity or not.

However I have two 59w panels linked so nearly 120w. Together they will easily reach and sit on 8 amps. So the 130w panel should do more than that.

This formula will give you an idea of max output in a perfect system (which you will never achieve due to heat losses etc).
Amps=watts/volts

depending on who made your panel....... the reported output watts (and amps) may not be the same, confused?

ok in theory all you need to out put 5a@12v is a 60W panel 5amps x12v=60W But depending on how "honest" the seller is about what the panel can put out you can get a lot of variance.

the nominal charging voltage for a generic 12v system is 13.8V so to me to put 5a into a 12v system you really need a 70w panel But thats only really good in ideal conditions add 10% to that and now you're looking at an 80W panel to put 5A into a 12v system.

then youve got the losses through the regulators.

the big advantage to a 200w panel over a 130w panel is simply that it puts out another 6A @12v however depending on the construction of the panel you may loose all of the output if just a small portion of the panel is covered.

Mornin!


soooo,, its OK to put 38V thru my batteries?

late edit,,
well no its not.
my controller has a max open circuit voltage of 26V

heres a (maybe dumb) question, do 2 panels double the voltage input to the controller?

need a voltage regulator, like the Morningstar range.

Oh and as for your doubling the voltage, if you wire them in series then yes.

Vern
I would be using the standard solar connectors, so just one set of cables to deal with inside,,
what does that make it?
though with voltage reg it makes no difference,,

Originally Posted by Pedro_The_Swift

Mornin!


soooo,, its OK to put 38V thru my batteries?

late edit,,
well no its not.
my controller has a max open circuit voltage of 26V

heres a (maybe dumb) question, do 2 panels double the voltage input to the controller?

depends on how you wire them.

theres a handfull of numbers you need to know.

1. full short amps. this is how much the panel will try to pump out if you just short the output, all your wiring needs to be able to handle this if you dont have fusing or circuit breakers at the panel. its aslo the maximum amps that can be pushed through the panel if you have a string of panels
2. rated voltage, this is the nominal voltage the panel works best at
3. rated watts, in theory the best out put the panel can achieve
4. rated amps, in theory the designed amps out of the panel at the nominal voltage (2,3+4 should more or less follow ohms law)
5. open circuit voltage of the panel, what it puts out with no load on it
6. maximum voltage of the panel, if you hook a string of them up in series this is the maximum voltage the insulation can handle

typically, a panels open circuit voltage will be its nominal voltage +~50%

very very roughly when it comes to wiring them up think of them as batteries and the usual rules of parallel and series apply.

If your battery is flat enough (and can handle the amps) you can hook a panel set rated a lot higher than the battery voltage as the load of the battery taking charge will pull the voltage from the panel down and the amps will increase. This gets hairy as the battery charges up and the process reverses (volts go up amps go down) as eventually you'll boil the batteries.

This is what your charge regulator takes care of.

No you shouldnt put a panel onto a regulator if the panels open circuit voltage is higher than the regulators max input voltage.

My personal preference is to run multiple panels with multiple small regulators, The advantage of this is that you always get something out of the system and you can piecemeal the system up to the required out put. It costs more in the long term, less in the short term (if you build in stages) but is cheaper to repair and upgrade. one other advantage is that it lets you run mismatched gear.