Solar The Solar Panel Thread

Fallen

New Member
Feb 7, 2019
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3
WA
To clarify, voltage didn't go zero when current went to zero. When I said "went to zero on both" i meant on both the screen of the TPS and on the meter. Sorry for the confusion! Voltage was the same.
Equally, the negative current on the panel may have been me having the leads the wrong way around. Will confirm next time the sun is out on the roof so I can get a more consistent set of numbers.
And yes, roof top was in partial shade in arvo so very low current compared to what it's provided before, and portable was in full arvo sun (with a bit of cloud).

Re diodes, pics attached! The info stated in the ads for these panels is typical cheap panel lingo: "foldable module is equipped with diode bypass technology, which helps to minimize power loss due to shade and guarantees reliable power supply in low light conditions".

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mikerezny

Well-Known Member
Sep 11, 2016
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Mount Waverley, VIC
Ok, thanks for the photos.
Your portable solar assembly consists of two panels wired in parallel.

Each of these panels consists of two sub-panels wired in series. You can tell this because, in the terminal block, there are three silver threads coming from the solar cells. One sub-panel terminates on the LH and centre terminals, the other on the centre and RH terminals.
There is a bypass diode across each of the sub-panels.

This is a quite common setup. But I can't see the point in having the bypass diodes. If one sub-panel is shaded, then the panel will only produce about 10V which is not enough to drive a solar regulator.

This panel would be an ideal candidate for wiring the two panels in series and feeding them into an MPPT controller. The cables appear to be on the light side for carrying 10A over any distance. Then leave the TPS controller for managing the roof panel.

But that doesn't solve the mystery of the parallel panels. Still two candidates: blocking diodes or a faulty controller.
Still need some better tests with all panels in reasonable sunlight without connection to the controller.

cheers
Mike
 

jazzeddie1234

Active Member
May 19, 2016
149
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Mandurah
Yes the current could be much higher, but only (for example) when the batteries are discharged and the solar controller is bulk charging, or where you have something like an inverter drawing lots of current. Otherwise the batteries may charged and the controller switched to trickle charging
 
Likes: mikerezny

Boots in Action

Well-Known Member
Mar 13, 2017
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Ferny Grove, Queensland
Yes the current could be much higher, but only (for example) when the batteries are discharged and the solar controller is bulk charging, or where you have something like an inverter drawing lots of current. Otherwise the batteries may charged and the controller switched to trickle charging
Agreed @jazzeddie1234 . Two of the readings give a good indication of what is happening at that moment. Panel voltage of 18 volts indicates that the load is indeed light (or batteries are fully charged). Panels are rated at Vmp and Imp ie 16.4V x 6.7A which equals the rated panel output of 110 watts. With low or no load, Vmp rises and the total output of only 4A (1A from each panel in parallel) certainly indicates trickle charging or Float situation. Also Vmp tends to remain higher when panels are cold. IMHO, a good position to be in.