Solar Panel Size

dorian · Guru

Solar Panel Size

Murraman · Senior Member

We have a Toyota Coaster with 2 x Solar Panels on the roof, They are connected to a Solarex sc-18 charger then on to the batteries. Batteries are 2 x 75 amp/h deep cycle.

It seems to be doing its job as per the booklet. What has me confused is the Gent we bought it off said the panels are 180w ea. Now to me it is going through an 18 amp charger and the numbers don't add up. That would mean it would need a 30 amp charger to run it.

What I'm thinking is they are 90w ea with total of 180w which would be 15 amp, And the Solarex sc-18 can handle that.

How do I work out what the panels are out putting or their wattage. They are approx 1m x .7m ea with 36 cells in each. I have no documentation at all on the panels but all relevant books on all other hardware. Am I working it out wrong?? The panels have no specs written on them that I can see.

Any input appreciated.

Cheers

oldtrack123 · Guru

HI

The panel "output Amps" will be the panel watts divided by 17V [360W/17V=21A] ,but you will only get that when the sun is very bright or with highly reflective clouds

The Solarex will probably cope with it.'the worst you can do is cook the regulator

THe panels should have a label or an output grraph on the back .

THe "PANEL AMPS output "will not be higher with a battery with a low SOC

Just see how it goes or buy a bigger one

It will not damage the panels!!

PeterQ

-- Edited by oldtrack123 on Wednesday 9th of October 2013 10:50:22 PM

-- Edited by oldtrack123 on Wednesday 9th of October 2013 10:53:33 PM

allinone · Senior Member

Hi Murraman, I have momentarily seen my 120w panel inputting 11A into the regulator so I would think that if you had 180w your regulator would soon fry on a full sun day and a low charged battery.
Do you mean a regulator or a charger?

Murraman · Senior Member

It makes sense what your saying and I tend to think they maybe 80w each. As to looking underneath it would be a PITA to remove them from the roof. Just trying to work out what size they were and from what I have been reading the output should be around 450 w from both up north in winter.

Thanks for all the input.

dorian wrote:
If each of your 0.7 sq. m. panels were producing 180W, then that would be equivalent to 257W per sq. m, or an efficiency of around 26% (the sun produces around 1000W per sq. m.)

A 90W panel would be producing 128W per sq. m. which is more in line with current technology.

www.outbacktravelaustralia.com.au/camping-power/camping-power

"Solar panels convert sunlight directly into electricity with an efficiency between 7 percent and 18 percent, which isn't very good. Of the bright sun's 1000 watts per square metre of energy, a one-square-metre solar panel can convert this into 70-180 watts of electricity, depending on the type of panel and the angle at which it's disposed to the sun's rays."

-- Edited by dorian on Wednesday 9th of October 2013 03:04:19 PM