Help help help! Solar panels installation

[tomandsophie]

I have received my lovely shiny new US-64 (64w Uni-Solar) solar panels and Steca charge controller. I'm very excited and can't wait to install them.

However, I came across my first hurdle upon opening the box and reading the manual. The manual shows a little junction box with 6 screw-type connections in the back of each panel. On the actual panels however the junction box looks very different. In fact, it is simply a box with two thick leads coming out of it (obviously 1 +ve and 1 -ve) with weird-looking connectors on the ends (they look a lot like co-axial cables, like TV arials have). That is it! No other leads and no space for any others to be added.

This would be ok if I was only connecting one, but I have bought two of them and want to wire them up together. What do I do?!

Help! I want to do it this weekend, and I need to go out and buy the cables. Which brings me to my second question - what diameter cable should I get? It will be about 3m to the controller, and then 2m to the batteries.

[Ricardo]

You need to connect the panels in parallel, connect all the +ve wires together and all the -ve wires together, either at the controller, a junction box or on the back of one panel.

 

You need to connect the controller to the batteries before connecting the solar panel so that the controller can automatically set itself for 12 or 24 volts.

 

I'd use thickish lamp cord if it was me but no doubt someone who actually knows what he's talking about will be able to give you actual numbers and stuff.

 

Ric.

[Gibbo]

You need to connect the panels in parallel, connect all the +ve wires together and all the -ve wires together, either at the controller, a junction box or on the back of one panel.

 

You need to connect the controller to the batteries before connecting the solar panel so that the controller can automatically set itself for 12 or 24 volts.

 

I'd use thickish lamp cord if it was me but no doubt someone who actually knows what he's talking about will be able to give you actual numbers and stuff.

 

Ric.

 

Seconded.

 

Use 4mm cable for both runs. Also try to keep both panels pointing in the same direction, otherwise when one gets bright sunlight, and the other one doesn't, the one that doesn't will "rob" the power from the other one. A bit like installing one without a diode, the batteries can (admittedly only a bit) discharge into the panel during darkness.

 

Gibbo

[Ricardo]

Seconded.

 

... try to keep both panels pointing in the same direction, otherwise when one gets bright sunlight, and the other one doesn't, the one that doesn't will "rob" the power from the other one.

 

 

I'd never thought of that, and I was going to put one on each side of the boat so I always had one in the sun!

[Carrie]

I'm going to try and post pics of my own solar set-up today if I can get out the boatyard later today (having section of waste tank cut out), if that can be of any help (will be on my forum blog).

[tomandsophie]

Thank you everybody. I will go out now and buy some nice thick cables, and I will see if I can find a match for the weird connectors that are on the panels' leads.

Here is a picture (hopefully, if I can work out how to attach it!) of the two ways I figure I could do the wiring. I guess the top one with the junction box would be neater and use less cabling overall, but the bottom one without the juntion box would be less complicated - which is good for me because I'm only a beginner when it comes to electrics!

 

Oops, that didn't work, I'll just find out how to attach the pic and we'll be away...

 

Edited January 13, 2007 by tomandsophie

[Carrie]

I put my pics on my blog, but without useful info - sorry. Good luck Tom and Sophie!

 

I've just noticed a difference though. One of my panels is wired to the second one and only this one is then wired down to the batteries....

[tomandsophie]

Hi Carrie, thanks for trying anyway! I have looked carefully at the panels and found that it is not possible to wire one to the other. Each one only has two cables coming out of them and no other connections. Hence the junction box idea. I'm in town now (good old laptop!) so I think I'll buy the junction box bits and pieces. I'll let you know how I get on...

 

Tom.

[Gibbo]

I'd never thought of that, and I was going to put one on each side of the boat so I always had one in the sun!

 

You can do this but you really need to install a diode for each panel. But then you have the loss in the diodes

 

Admittedly this isn't much with a solar panel in the UK.

 

Gibbo

[Ricardo]

Suppose I wanted to do this and found myself in Maplin or somesuch place, what kind of diode would I ask for?

 

Thanks.

 

Ric.

[chris w]

For a 64W solar panel (ie: 5.5A @ 12v) get a 10A diode minimum. Most are silicon which have a forward drop of about 0.7v to 0.8v at that current. If you can, get a Schottky diode which will have about half the voltage drop of a silicon type.

 

Maplin part number N25CC @ 93 pence ea. is a Schottky 16A version for example.

 

click here: Maplin Schottky diode

 

Chris

[Ricardo]

Cheers, I'll start saving!

[Bones]

How did you secure your panels to the roof?

[tomandsophie]

They are mounted on a pallet each (one of the big strong heavy ones). I made up a strut and a small bracket to hold each of the panels up at 45 degrees to the horizon. Then the whole lot is tied and locked to the roof using rope and cable-locks.