Solar Panel Gauge Showing Charge at Night ?

[Dulcesuenos]

Ok went to the boat 10 am , it was raining and extremly overcast, wind gen ammeter showed .5 or lower . Solar panel gauge was reading 3amps In overcast and rain and battery voltage was up to 13.3 v. I checked batt voltage with multi meter. It was correct.. Still baffeled. We r not hooked to shore power.

[callmecrazy]

maybe the readings are backwards? windgen producing 3amps and solar producing .5 would make sense...

[Snore]

While I am not a boat solar panel expert, solar panels on temporary traffic signs (arrow boards) will continue to trickle charge the batteries while in an enclosed garage with the door closed and only reflective light and fluorescent lights.

If the gauges test right, it may be possible that the moon light was just enough for the cells.

[s/v Jedi]

Let me repeat: verify meters with a Fluke multi meter. So, if a meter shows 3A, test for that current with the Fluke. There are 2 methods for that: 1) break the circuit and insert the Fluke in current mode, or 2) measure the DC voltage over the shunt and identify the shunt type (how many mV per amp). Measuring hattery voltage only verifies the battery voltage meter.

cheers,
Nick.

[senormechanico]

When we read 0.10 amp from the full moonlight, I didn't want to take it on faith, so I went outside into the 80 degree Mexican night and threw a towel over the panels.
Sure enough, the Cruising Equipment Quadcycle current scale read 0.00 amps.

[noelex 77]

Originally Posted by senormechanico

When we read 0.10 amp from the full moonlight, I didn't want to take it on faith, so I went outside into the 80 degree Mexican night and threw a towel over the panels.
Sure enough, the Cruising Equipment Quadcycle current scale read 0.00 amps.

0.1A from moonlight is just impossible.
There are a lot of reasons why the quadcycle current scale was reading as you describe

The most likely explanation is the meter reads 0.1A too high and there is 0.1A self consumption from the regulator. So with a towel over it it should read -0.1A, but the 0.1 error means is reads 0.0 as you noted. At night the regulator goes to sleep and the self consumption disappears It then reads +0.1 when the correct answer is 0.0

There are many other possibilities such as the meter has a negative temperature coefficient, or there is some induced current in the shunt wires from something on during the day etc etc

[noelex 77]

Originally Posted by senormechanico

When we read 0.10 amp from the full moonlight, I didn't want to take it on faith, so I went outside into the 80 degree Mexican night and threw a towel over the panels.
Sure enough, the Cruising Equipment Quadcycle current scale read 0.00 amps.

0.1A from moonlight is just impossible.


The resolution of the meter is just not accurate enough to come the conclusions you doing.
Our eyes respond to illumination in a logarithmic way. This is why solar output drops dramatically when our eyes only perceive a small change in illumination.

There is very little energy in moonlight. Solar panels do not make energy they simply convert light energy into electrical energy. There is nowhere near enough energy in moonlight to generate 1w from a few square meters.

[Seahunter]

Originally Posted by senormechanico

When we read 0.10 amp from the full moonlight, I didn't want to take it on faith, so I went outside into the 80 degree Mexican night and threw a towel over the panels.
Sure enough, the Cruising Equipment Quadcycle current scale read 0.00 amps.

This is absolutely possible and I've seen it before. Depending on brand and size of the panels one can easily produce electricity under a full moon, especially in southern latitudes. EG 48V panels to 12V at 200W panels can produce .1 - .2 amps. Before we move to our boat, our solar powered (off grid) home produced nearly 100watts under a full moon. It's a misconception that solar panels need direct sunlight; all they need is light.

[noelex 77]

Originally Posted by Seahunter

Before we move to our boat, our solar powered (off grid) home produced nearly 100watts under a full moon. .

Oh Dear this is getting worse
Soon we will have someone planning to run their boats electric engine on moonlight.

The energy in moonlight is not difficult to find. Here is a typical reference.
http://www.madsci.org/posts/archives...96879.Ph.r.htm

1 milliwatt per square meter.

If your solar panels were 100% efficient and converted all that energy into electricity you would need a 100,000 square meters or a solar array 1Km X 100m ( About ½ a mile long and 100 yards wide) to produce 100w

[senormechanico]

Noelex,

I admire all your math etc, and you sound knowlegeable.
However, a Cruising Equipment Quadcycle Regulator (again, previous boat) was built in the early 80's and was a monitor. The only "regulator" function it had was for the alternator. There was NO sleep function per se.

Our current boat has a MPPT controller.
I'm going to start smelting aluminum with all the extra power.

[noelex 77]

OK one last try.
Forget the math’s here is a practical example.

Get a good quality Cree 1w LED torch. Adjust the beam (or distance) so it is same sizes as your solar panels.
This we be much, much brighter than moonlight.

Now we know the torch is consuming 1w. If the torch was a 100% efficient in converting electricity to light (with no heat etc produced) and the solar panels were 100% efficient in converting the light back to electricity (in reality about 15%) with no losses in the wiring etc.
Only with this hypothetical 100% efficient system then could we get 1w (a bit less than the 0.1A you are reporting). We cannot get more energy out than we put in.

How then do we get over 1w out of moonlight, which is much less bright than the torch, in a system with real world efficiencies?

[Seahunter]

NoeleX, while not as full of jovial platitudes as Steve B, your dithering could be harnessed providing at least enough energy to produce a couple of ice cubes for my scotch. I could care less whether or not you believe energy can or can not be produced from reflected sunlight (moonlight) or not. Yet the fact that your blither blathering myopic views struggle to make any sense, ideas not put to any practice, merely based on premise, do not in any way make it an untruth that solar panels can and do produce electricity from moonlight. By the by, most solar panels produced today are 120% or their rated value, and understanding that most solar enthusiasts benefit.

[senormechanico]

I'm not jerking anyone's chain, but 100ma from the moon HAPPENED.
The moon was high overhead, full and it was on Mexico's West coast. Tenacatita to be exact.
I understand perfectly digital display's resolution and offset etc as well.

It was a full moon a couple of nights ago, maybe tonight I'll set up a 20 watt panel I have lying around and hook it up to a 12 volt battery and set my fluke in series with one lead on a 300ma current setting and see what I get.
With only a 20 watt panel, I certainly won't expect 100 ma, but it's worth it just for fun.
Maybe someone else might want to try the experiment as well.

Sorry for all the thread drift.

[GordMay]

Originally Posted by senormechanico

... With only a 20 watt panel, I certainly won't expect 100 ma, but it's worth it just for fun.
Maybe someone else might want to try the experiment as well.

The Earth’s Solar insolation is roughly 342 Watts per square metre.
The Earth’s Lunar insolation is about 1 milliWatt per square metre, or about 1/342,000 the intensity of sunlight.

Accordingly, it may be conceivable that a 20 watt PV panel might capture something like 0.0000584 watts (0.0000048 A @ 12V) under full moonlight; but I doubt that any of us will accurately measure it.

[Dulcesuenos]

Just an update, last night, no sun > the gauge was showing 0. Not sure what caused the misreading it was a very moonlit night that night. I never did check with a fluke meter but I shall as soon as I get one.