Paseo gets a solar sun roof

[Christ]

What does a PV panel produce when it draws current? Heat?

[Daox]

Thats an interesting question, and I have no idea what the answer is.

[Christ]

I've done a bit of searching, and can't find anything except everyone saying that it will magically drain your battery at night if you don't install a blocker. Harumph.

[Daox]

I went out and measured the voltage and something is obviously wrong. I got a reading of 10.4V. Right now the panel has way more sun than it did in my living room, so I'm going to have to look into what went wrong.

[Christ]

Maybe the glass is filtering the light?

If you set it on your trunk, does the reading increase?

[Daox]

Back when I built the panel, I had it sitting in my living room on a cloudy day and it was generating over 12V. I don't think its being filtered. I'm thinking there is perhaps some tabbing material shorting across some of the cells. I cleaned some of the excess up, but left some too thinking it probably wouldn't hurt anything. All the jostling around in the car may have moved the tabbing and is causing current to bypass some cells.

[Christ]

Originally Posted by Daox

Back when I built the panel, I had it sitting in my living room on a cloudy day and it was generating over 12V. I don't think its being filtered. I'm thinking there is perhaps some tabbing material shorting across some of the cells. I cleaned some of the excess up, but left some too thinking it probably wouldn't hurt anything. All the jostling around in the car may have moved the tabbing and is causing current to bypass some cells.

Also possible. I only suggest filtering because your car's windows are designed with a layer of plastic between two layers of tempered glass, and are at a fairly odd angle.

However, your idea sounds more likely to create that much of a drop.

[Daox]

I took some time this weekend to finish up the panel. I ended up going with hot glue to adhere the cells, wire, and diode to the board. I'm not sure this was a great idea due to the low melting temperature of it, but we'll see. Again, on an overcast (but light at least) day, it was producing upwards of 17V. I then hooked it up to a computer fan and the voltage dropped to 7V and .14A. So, still not putting out the power it should, but it was overcast too, so I'll need to do further testing to make sure its going to work out good.


Cells all glued in place. No more rattling around. I check the tabbing and cut any excess off that I thought might short cells.





I also shortened up the leads and put connectors on the ends. This will allow easy removal from the car if/when I need to.

[MetroMPG]

Originally Posted by Christ

What does a PV panel produce when it draws current? Heat?

Silly question. Sunshine!

[Christ]

Originally Posted by MetroMPG

Silly question. Sunshine!

I asked because LED's, when exposed to light, will produce a very low current voltage output. Yep, they produce electricity! They're very inefficient as electricity producers, but very efficient at producing light. I wondered if a PV cell was somewhat the opposite, if it's fairly efficient at producing electricity, but if you apply electricity to it, will it become a very inefficient light?