solar panel output

[sandovalch]

I have built 10, 36 cells panels (2.75A at 18.5V) with the e-bay cells and would like to know what the charging amps of each panel should be? Does it depend on the charging state of the batteries? I have a C35 charge controller hooked between the panels and the batteries.

[ghurd]

Charging amps should change very little due to the battery SOC, until the regulator starts slowing it down at the SOC close to 'full'.

The variation in amps is probably more related to clouds, humidity, sun angle etc.

Check data sheets for a similar factory made panel.

Example from the 75w Photowatt panels I am wiring up right now:

With 0v (short circuit) amps is 4.7

At peak power (17v) amps is 4.4

Open V (0 amps) is 21.6

If the 12v battery is even at 6 volts, mabe it gets 4.5 amps.  If it is at 16v, you get 4.7 amps.  That's only about 5%.

G-

[ghurd]

OK Oops. switch the 4.5 and 4.7 in that last sentence.

G-

[sandovalch]

And if I have a voltage drop of about 1.5V due to cabling, does the current stay the same?

[johnlm]

If you have a 1.5V drop due to cabeling it will reduce the maximum current somewhat.  That 1.5V drop is due to the resistance of the wire in series with the panel and charge controller / battery bank.  Any time you add series reaistance it goes toward reducing the maximum current.

[Dennis the bus dweller]

Hello folks

Im a newcomer on the your site. I live off the grid in a converted school bus here in N.Y. I have 1200 watts of PV panels and a small Air-X wind turbine that keeps 24/6 volt deep cycle golf cart batteries ( wired for 12 volts ) charged. Even on a nice sunny winter day ( winter days are much shorter and cloudier then summer day ) I pull in about 40 or 50 amps and if the little turbine starts up I get a little more. If im lucky enough to get a 30 mile per hour wind the Air-X turbine will put out 39 amps all by it self ( never happends here though ). I would have to go up and look at what each 110 watt panel puts out to help with your question though. But do remember, What it says on the panels, is in a perfect world. It's still great stuff though. I bought all my panels used for about 3.50 per watt on ebay. There all about 4 to 5 years old when I got them but unless you brake them they last a really long time. Just my 2 cents.

Peace along the way

Dennis the bus dweller N.Y.

[richhagen]

For some reason I've been getting no output from my panels the last couple of days, could be the foot of that white stuff TomW was complaining about on top of them has something to do with it though.  Rich Hagen

[troy]

Copious white polycrystaline dihydrogen oxide seems to interfere with the photoelectric effect of mono or polycyrstaline doped silicon.  Mechanical removal is reported to minimize that neutralizing effect.

From the technical language obfuscating dept,

troy

[richhagen]

Not looking forward to that mechanical removal procedure because of the lack of thermal energy and the resulting heat transfer.  Rich Hagen

[RatOmeter]

You just don't want to get out in the cold, eh?

[ghurd]

Every mono or multi panel I ever tested under 'real good' conditions put out slightly more than what the sticker said, even if they were a couple years old.

Amorphous PVs seem to wear out quite fast. Never saw one that would do it's rating if it was a few years old.

G-

[richhagen]

Yep! Rich Hagen

[pyrocasto]

Would Rainex not help that problem of the dyhydrogen monoxide in the solid state, to remove itself, without blocking too much useful uv radiation? That would not force you to mechanically remove it, which in turn results in a negative thermal heat transfer.

Or maybe wax?(doubtful)