So I have a Harbor Freight 100w Solar kit laying around and plan on using it as a moble solar array.
Has anyone tried wiring these panels in series?
I am thinking about wiring two sets of 25w 18v panels in series = 36v then paralel to each other as I have an MPPT controler.
It appears the panels can take it.
One of my concern is the size of the factory wiring, not sure its gauge.
Anyone with and relevant experience?
If you connect them all in parallel then you'll get maximum current to battery. 18Volts is enough voltage for the controller to work just fine. More just requires that the controller burns up more power. The charging current of the panels in parallel is probably 6 to 8 amps. If you split it up like you're talking about the charge current will be somewhere closer to 3 amps.
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If you connect them all in parallel then you'll get maximum current to battery. 18Volts is enough voltage for the controller to work just fine. More just requires that the controller burns up more power. The charging current of the panels in parallel is probably 6 to 8 amps. If you split it up like you're talking about the charge current will be somewhere closer to 3 amps.
Using an MPPT controller you can connect them in series, have 36v running from the panels (less voltage drop), and still get the full amperage to the batteries. The MPPT controller acts as a DC to DC converter, dropping the voltage as needed for charging while increasing the amperage at a very high efficiency level. Your MPPT controller must be rated for the max voltage and current involved.
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In a small system with short wire runs it makes little difference. In a larger system, or especially one with long wire runs to the panels, the higher voltage while using a MPPT controller can work better.
One thing to consider however is that a panel is already a collection of PV Cells in series. If one cell is shaded (just part of the panel), then the output of that panel drops drastically, usually to about zero. If you put panels in series, then ALL the cells in both panels are in series and any shading on any single cell affects the entire system. If you put the panels in parallel, then if one panel has one or more shaded cells, then that does not affect the other panel. if the other panel(s) is/are still in the sun then you at least get the output from those panels. In other words if you put your pair of 25 watt panels in parallel you can get as much as 50 watts out, and if one panel is shaded but not the other you get half. Put them in series however and you get about the same output in full sun, but one shaded panel pretty much kills the output of the entire system.
In a small system with short wire runs it makes little difference. In a larger system, or especially one with long wire runs to the panels, the higher voltage while using a MPPT controller can work better.
One thing to consider however is that a panel is already a collection of PV Cells in series. If one cell is shaded (just part of the panel), then the output of that panel drops drastically, usually to about zero. If you put panels in series, then ALL the cells in both panels are in series and any shading on any single cell affects the entire system. If you put the panels in parallel, then if one panel has one or more shaded cells, then that does not affect the other panel. if the other panel(s) is/are still in the sun then you at least get the output from those panels. In other words if you put your pair of 25 watt panels in parallel you can get as much as 50 watts out, and if one panel is shaded but not the other you get half. Put them in series however and you get about the same output in full sun, but one shaded panel pretty much kills the output of the entire system.
Understand, however the Harbor Freight panels are the amorphous type which handles partial shade better. They are heavy glass panels but the idea is to use this kit as portable panels to move them into the sunny parts of the camp site.
Using an MPPT controller you can connect them in series, have 36v running from the panels (less voltage drop), and still get the full amperage to the batteries. The MPPT controller acts as a DC to DC converter, dropping the voltage as needed for charging while increasing the amperage at a very high efficiency level. Your MPPT controller must be rated for the max voltage and current involved.
Yup all three amps.
Think Watts = Watts= Voltage*current. Or current = voltage/watts No matter how hard you try the the laws of physics are still the laws of physics.
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