12v <span class="highlight">solar</span> on roof of 4wd

I would guess the battery is nearly full discharge it a bit or put a reasonable load on the battery then see how the panel goes
Cheers steve

Where is your regulator? On the panel or close to the battery. The closer to the battery the better.
regards

Melbourne is well south and at this time of year has a low sun.Melbourne autumn weather is often sunny and glorious to be outdoors in, but often very hazy, which can have a big effect on PV output. Horizontal panels on the roof of your vehicle at low latitudes in late autumn with possibly hazy sun - you have everything working against you.

Having said that, I would have thought you'd get a bit more than 12 to 19 watts.

If you can move your panel, try getting it pointing directly to the sun - shadow directly behind the panel and the shortest possible shadow length - and see if that makes a difference.

Cheers

Something is clearly wrong so it should be fixed well before considering the small improvement MPPT provides.

I will assue here that you don't have much test gear otherwise I say to put a good load on your panel and measure current , so here is a simple way to test it.

First if the whole panel is in sun (not shaded) then you should be getting a minimum of 60+ watts out of it from 11 till 2pm.
Thats out of panel with no regulator connected.

To check this get a dirt cheap car headlight globe (70-120w) , disconnect panel from the rest and put globe across the panels output wires , it should glow brightly and with luck blow the globe (hence cheap is good).

The above tells you the panels ok , I'd have to know more about any test gear , and or how the regulator is connected to go further.

P.S. I save my headlights globes if just high or low beam fails for just these sorts of reasons.

I am no expert on solar but your figures sound more like Volts, not Watts, 19 volts unregulated will give you something like 7amps output ( I think).
How did you arrive at the 12 to19 w figures ?

Someone please correct me if I am wrong.

Scrubby.

So I have tested the panel directly and it's working fine. Was putting out 21.6v and it is putting out 14v after the regulator into the battery but it still only produced 28watts when i tilted it towards the sun at midday? Maybe my reg is buggered?

Magoo something is amiss here and I think it's in the way you are reading the outputs from your panel.

On a 125 Watt panel, the specifications are thus;

Mono-Crystalline 125W
Max Power Voltage 17.8V
Max Power Current 7.02A
Open Circuit Voltage 21.9V
Short Circuit Current 7.58A
Module Efficiency 17.3%


The output from the panel is measured in Volts and amps, not watts. The maximum ampage (electrical current) output by the panel is a bit over seven amps at 18Volts or a little higher if you run the panel as open circuit (no controller on the panel).

Your output of 19 VOLTS is pretty much spot on. Your ampage (The electrical current output from the panel) should be between 5 and 7 amps. It's not Watts and that's what is causing you the confusion.

Generally, when you're talking about watts (W) in the context of electrical power, you're talking about instantaneous power generated or consumed by a given device: How much power is being generated or used at a given moment? your 130 att panel will produce 130 watts of power each hour in PEAK sunlight and in optimal conditions. Normally it's lower than this because of the angle of the sun, the panels and other factors.

Watts = amps x volts so in the case of the panel above 17.8 x 7 = 125 (ish)


Have a read of this article it's excellent for demystifying solar;

Electricity for camping

Cheers

Is the panel rated 130w at 12V or 240v? It will tell you on the back. If it is rated at 240v than it will only produce 6.5W at 12v. Don't waist your money on a MPPT controller as they are only a benefit for large systems. There are articles on the net that explain why.

To test the panel, remove the regulator, face the panel at bright sunshine, using an amp meter that can handle the current to a short circuit current test across the panels terminals, ie place the red probe on the positive terminal and the black on the negative terminal at see what it reads, you should get the same as shown on the panels label for short circuit current or there abouts.