80 Watt Solar Setup

You are correct it's got a 10m lead

Outsider,

I did some more testing last night and I replaced the dodgy clips that came with it with some good quality ones and re soldered the wires etc etc. I then took a volt measurement at the battery and it was 12.4 and I also put it at the other end at the panel and it showed 12.3...so 0.1 drop is probably not to bad over 10 meters?

Let me see if if I have this right
If I was to move the controller does that mean I will have to run 2 sets of wires still?
join the 2 panels together and run one long cable to the controller and then a thicker much shorter to the battery?

"join the 2 panels together and run one long cable to the controller and then a thicker much shorter to the battery"

That sounds right to me.

I would be surprised if you were only getting a voltage drop of 0.1v over 10 meters

Troll,

Are you saying you have two (2) POS (+) & two (2) NEG (-) cables going to the battery ??

"If I was to move the controller does that mean I will have to run *2 sets* of wires still"
"join the 2 panels together and run one long cable to the controller and then a thicker much shorter to the battery"

Wire the two panels together, then run just one *set* of cables to the solar regulator situated at the battery, with same cable size all the way.

Maîneÿ . . .

when the fridge is not running, what's happening to the battery ????

Maîneÿ . . .

Will let you know...I am going to buy a clamp meter soon so will have more accurate figures. By the time I get home it will be around 4pm and I am guessing the sun won't be at it's optimum but will record the numbers and let you know

Ed C,

you can verify their (un)accuracy, by wiring a cheapish multimeter into the circuit for testing purposes. Read on if this if of interest to you...

A few general comments first:
Clamp meters can introduce large errors at low currents.

E.g. if the accuracy of a 4000 count unit is specified +/-1% of reading + 1 LSD for DCV, then the same meter could have a much worse accuracy of e.g. +/-2.5% of reading + 3 LSD for DCA.
In other words, measuring say 20VDC, your meter could show anything between 19.79V and 20.21V which would be sufficiently accurate for most jobs.

But if you'd measure a 40W solar panel's output current of around 2.5A, the meter could show anything between 1.44A and 3.56A, or +/- 42.4% of the expected value which is a large and significant deviation from the real thing.

Using conventional multimeters on their DCA setting gives a more accurate picture, but care has to be taken to keep probe wire/clamp resistance as low as possible in order to prevent excessive voltage drop (which would reduce the battery charging current quite a bit).

Whenever I do current testing on battery charging circuits, I like to wiggle the banana style plugs inside their receptacles several times. This scratches off any contact surface oxidisation, resulting in a much more accurate reading.

Best regards, batterymeister

oops, error on my side:

the current measurement would be out by up to +/- 92.5mA, so you could expect a reading of between 2.41A and 2.59A which is quite an acceptable range of uncertainty.

My apologies.

Best, batterymeister

I ended up stopping at Dick Smiths on the way home and picked up a good one I think. I have been looking at the ones on eBay for a while but I think those $20 ones wont be very good and the accuracy will be poor.

It's always advisable to compare specs and accuracy figures.

If I'd be in the market for a DC current clamp meter with reasonable accuracy, I'd go for the directly imported ones on ebay.
The importer has a full specs sheet there, together with detailed and meaningful accuracy figures - something I don't get to see at jaycars more expensive offerings.
No data no deal :(

Best regards, batterymeister

I would be interested in the panel angle,
I had read that here in brisbane around 26 degrees facing north would be the best angle but after testing I have found that this time of year laying the panel flat produced the most amps.

Quite often see folks with their panels up around 60 degrees, doubt they would be very efficient at the angle.

My main panel is flat on the roof of the jeep !! So I lose the first and last hours of sunshine - From memory I think the angle has something to do with your latitude ? Rule of thumb ?
But that angle would need to be changed during the year to be aligned with the sun .. Might try a couple of different angles as well tonight ..

Cheers

Steve

If the shade at the rear of the panel was the same or similar dimension as the panel then the angle to the sun would be right....correct ?

At midday (sun time ) Yes ...

What you need is a rod mounted at right angles to the panel and keep its shadow to a minimum - then the panel will be pointed at the sun correctly ..

Cheers

Mandrake

Ideal positioning is facing 'solar' north (as opposed to magnetic north)
With the angle set at your location latitude.
BUT- this only applies at equinox.
So on the equator- the panels would be set horizontal- and at the poles they would be vetrical.
Equinox is aslo the only time a sun-dial is accurate. not allowing for the +/- calculations required !!

Another way to obtain the optimum angle:
Stick a stick in the ground.
Measure the length of the stick and divide this by the length of the shadow cast.
This would give you the tangent of the required angle when subtracted from 90 dgrees.
Also, the direction of the cast shadow would indicate solar north at that moment.

eg. At my location (just SW Sydney) at 12.24pm AESST- a 300mm stick cast a shadow of 90mm.
The tangent resulted in an angle of 73.3 degrees. Subtracted from 90 would yield an optimum angle of 16.7 degrees.
This would be correct as the Summer Solstice was only a month ago.

Due to severe overcast conditions testing is postponed for a day or so ...

"It may not happen overnight but it will happen."

LOL

Mandrake

OK - Clouds went away and I got the Kit out and set up for tests ..
2 X 50 watt Solar Kit at 20 degrees to the vertical facing the sun .
Manufacturers data as supplied
Short circuit Amps 2.96 X 2 = 5.92 Amps
Short Circuit Voltage - 21.6 V
Rated at 2.77Amps at 18 Volts X 2 = 5.54 Amps
Ambient Temp was 22 C approx. ..
Time of test 10.30 am to 10.50 am .
2 different Multimeters which were changed to verify results ..
Amp measurements were taken between the +ve ali clip and +ve battery terminal.

This was not as easy as I assumed - My Multimeters were dancing all over the place
and was very ( impossible really ) to get any accuracy however the results are
interesting if not totally accurate ..

The constant load used was an old 12v auto fan-heater - running fan only.

BOTH PANELS .

Volts measured at controller input - between 19.7 and 20.3 .
Volts measures at controller output - 14.7 ( under constant load )
volts measured at Ali clip - 14.0 ( Under constant load )
Short-circuit Amps was 6.09
I tried to measure Amps but the range on the
display was flicking from 0.8 to 6.18 !!!

SINGLE PANEL ( 1 Panel totally covered )

Volts measured at controller input - between 19.7 and 20.3 .
Volts measures at controller output - 14.7 ( under constant load )
volts measured at Ali clip - 14.0 ( Under constant load )

Short-circuit Amps was 3.05

BOTH PANELS ( lower half of both panels covered )

Volts measured at controller input - between 19.7 and 20.3 .
Volts measures at controller output - 14.7 ( under constant load )
volts measured at Ali clip - 14.0 ( Under constant load )

Short-circuit Amps was 0.13 !!

So as long as one complete panel is in full sun the kit works well
Any amount of shade over both panels reduces output dramatically .

The cable supplied with the kit is 5 metres long and "obviously " not
large enough as the voltage drop was 0.7 volts !! Moving the controller
closer to the battery would solve that issue as would changing to a
larger diameter cable .

Cheers

Steve