DIY? Now I'm power hungry!!

rickeolis

My new system has been up and running for about a half a year and I was looking into getting more panels and found a guy on ebay selling just the cells: 230 watts worth for $300.00. That would be a sweet watt/dollar ratio, so I bought them.
My current system nets me about 40% of my home's needs per month (based on roughly 1200 watts) and I think this new panel if I build it right will add another 20% to my wattage.

Now I need to figure out how to build a panel using these cells. There are 100 3" x 6" cells without leads on them. (close to 2.4 watts each), I don't have them just yet, but his ebay feedback is great and I should see them soon.

I guess I'll need some solar cell soldering tape that I've seen for sale, as well as a diode (one shotsky 10 amp??), and a board to mount them on, then a plate of glass to cover the whole panel. Then to build a frame for it all. What else for parts?

Anyone do their own here? I have the soldering and electronic skills, but haven't tried this job before!
Thanks-

-Rick-

mike95490

Re: DIY? Now I'm power hungry!!

rickeolis wrote: »

Anyone do their own here? I have the soldering and electronic skills, but haven't tried this job before!
Thanks-

-Rick-

Build it as if it has to work 10 feet under water. Otherwise, it, and all your work will fail in a couple of years.

You need special lo-temp solder to connect to the cells, and an iron set to the low temp.

All has to be sealed to prevent water vapor getting into any voids. Water vapor will corrode your cells.

rickeolis

Re: DIY? Now I'm power hungry!!

Thanks-
I was thinking I might have to buy a special soldering iron and solder for this job, but that's fine.
Where do I put the diode? Inline with the positive just before it goes outside of the panel? +<

-Rick-

BB.

Re: DIY? Now I'm power hungry!!

There are two types of diodes in a typical solar panel... One is a blocking diode--typically just in series to block any "back current"--typically to avoid discharging the battery bank when the sun is not shining... Only required on installations where the panels connect directly to the battery instead of through a solar charge controller (charge controller should stop back current / leakage current into the solar panels at night).

The other is a bypass diode. Used when you have, for example, two solar panels in series (say two 15 volt panels in series charging a 12 volt battery bank) through an MPPT solar charge controller. This diode is across the +/- lead and, if one of the panels is blocked with shade--allows the other panel to drive current through the bypass diode and still get energy to the solar charge controller (solar panels go "high resistance" when there is no sunlight)..

Depending on exactly what you are connecting too--you may not need any diodes at all... But you should probably have a series fuse to prevent an internal short causing a fire in the panel or the wiring.

Both diodes can be mounted where it is convinent -- out of the weather and on a heat sink. They don't have to be mounted inside the panel.

If you choose to use a series diode--you only need one per string.

If you want a bypass diode--you need, at least one, per panel (depending on shading patterns, you can install more than one bypass diode to, for example, bypass shading on the lower 1/2 of the panel while the upper half is passing power---or you can put in two series strings without diodes--one string in the upper half of the panel and one string in the lower 1/2 of the panel--pretty much your choose based on panel sizes, cell sizes, and power voltage/current required.

-Bill

rickeolis

Re: DIY? Now I'm power hungry!!

Very informative reply, thanks!
I should have the blocking one in there at least.

-Rick-

BB.

Re: DIY? Now I'm power hungry!!

You really only need a blocking diode if you don't have a solar charge controller between the panels and the battery bank or some off-brand controller that may not have a (night leakage) blocking function in it...

The blocking diodes, otherwise just burn power (P=V*I) where V is the forward voltage drop and is usually between 0.2 and 1.0 volts and I is the current output of your string. Your I per string may be 2.4w/.5v=4.8 amps...

So your series diode will need to dissipate (wasted power per series diode) around 1-5 Watts (depending on diode used and forward current).

-Bill

wild01

Re: DIY? Now I'm power hungry!!

if these are the same cells that I just bought they will be made on the weakest substrate known to man. they have the tensile strength of a pringles chip. be careful picking them up, I had several that snapped under their own weight. I have bought individual cells in the past that were way higher quality.

rickeolis

Re: DIY? Now I'm power hungry!!

Thanks for the tips guys!

So, what do my Evergreen 180's have for diodes? I feel I should mimick that setup...

To be honest, I don't use a charge controller. I have a method that bleeds off voltages above the critical levels. I rarely ever get up there though because I use more power than I produce as of now.

-Rick-