The LED flashes, when on it takes most of the power from the panel, off the battery gets it. The LED flashes as when on it pulls the voltage below that required for the LED conduct so it stops this means the voltage rises to the conduction point, repeat.
The funeral will be at a crem somewhere, donno where the nearest/nicest is but it'll be 20 to 30 miles away minimum. Seems sensible to have the booze up nearer the crem than get everyone to drive for an hour. Doesn't bother me, I won't be there.
In other words, a faulty panel, one that's gone very high resistance in the photo-cell array cct to the extent that the couple of milliamps drawn by the self flashing blue LED indicator lamp is sufficient to drop the voltage below the 12v mark during its on period.
It's been a while since I last bothered to test my own panels but istr a short cct current in full direct sunlight of just over 100mA and around
80 to 90mA when charging a 12v SLA at around the 13.5 volt mark. At this current level, it was just possible to see the 2mA modulation effect from the self blinking blue led on an analogue multimeter.For something *this* buggered, it will be worth prising the rubber/ plastic bungs out to undo the screws that retain the case halves together and take a closer look.
If it's just a single cell out of the 30 or so that's gone HR, it's probably worth strapping it out and accept the slightly reduced charging current that results compared to its original spec. If you're lucky, it might simply be a corroded connection you might be able to make good one way or another. It's certainly worth taking it apart and taking a closer look before chucking it out (whether it's whole or 'in bits' makes no difference to the bin).
panel,
I was testing under my conditions ie north facing window overcast. B-)
Does the LED always flash or does it become steady in full sun? That would make sense as an indicator of charge being supplied but as you say you can always see the modulatoin it must always flash...
The sun is out and bright hang on...
Full sun 21 V open circuit, 90 mA short circuit. Full shade looking at blue sky 4 mA short cicuit, this is no doubt why it didn't really keep the gensets battery topped up.
Short circuit current drops to < 30 mA, (> 1/3) with more than 5 cells (1/6th) of the panel in shadow.
LED doesn't light at all... maybe I've got at it. B-)
Well, that answers your question as to why it's a "Jolly Good Idea" to run the 50 metres of connecting cable to resite the panel so it can see direct sunlight. Direct illumination from the sun, even at far from optimum angles, is far more efficacious than the view of a clear blue sky.
In this case, the volt drop from a 50 metre run of bell wire is not going to be of any significance (even when using a pair of these panels in parallel).
Yes, it keeps flashing under all levels of illumination that will generate 3 or more volts.
It only needs a single cell to be in shadow to sabotage the panel's output. The photo cell becomes very high resistance in the absence of light. When there is illumination, each cell acts like a voltage limited constant current generator.
It's absolutely vital that you avoid shading any one or more cells in a a serial connected array of cells since that will effectively disable the output from the whole array (it's not just simply a reduction by the half volt or so of lost 'production' from the shaded cell that's at work here).
I'm sorry, I can't quite figure out what you meant by that.
It doesn't need much output to light the self blinking blue LED. I've just taken my two panels out of the drawer and both light up their LEDs under room illumination (a 5 foot fluorescent lamp), producing about 5 volts or so open cct. The repaired one with a normal blue LED shows a steadyish 5 volts whilst the original unit shows voltage cycling between
5 and 7 volts or so in response to the 'blinking' load.The choice of a self blinking LED over that of an ordinary one is a wise one in that even if it appears dim by contrast to the illumination it must necessarily operate under (full direct sunlight), the blinking nature reveals unambiguously that the panel is behaving as expected.
A non-blinking LED (even a high efficiency 'hurts your eyes' blue one) doesn't offer such an assurance any where near as clearly - if I'd had a blinking blue led in my spares box, rest assured, I most certainly would have used it for the repair.
A non-blinking LED would require around 10 times more current than the
2mA (peak) or so taken by the blinking LED to achieve the same effect, sacrificing some 20% or so of the panel's output versus the 1% average of the blinking LED.
I shall have try it on an overcast day, I suspect that will be better but still next to nothing compared to full sun.
I played, shadowing one cell, the two, then three, etc. The output wasn't greatly affected by just one or two cells in shadow it wasn't down to 30 mA until 5 ot 6 cells were shadowed.
"Got at it" with a pair of snips...
Oh, I see. Well, it won't stop the panel working, just the indication that it's generating (some) output voltage.
I tried the shadowing experiment myself and was rather surprised that the effect wasn't quite as clear cut as I've been led to believe in the literature. Perhaps each cell has a "reverse charging diode" integrated or wired across it to mitigate the high impedance when shaded effect. Still, the advice to avoid the possibility of shadowing one or more of the cells is still worth following.
If my hypothesis regarding "reverse charging diodes" is correct, shading
6 cells effectively loses you 6 x 0.55v (3.3v drop in generated voltage) with a further volt drop due to the diodes (6 x 0.7v = 4.2v) giving a charging voltage loss of 7.5v in all which would seem to be about right to fit in with your observations.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.