Solar Panel Install/behavior

[Witzend]

I just installed the Coleman CL-3900 with CC-4000 charge controller on my boat. Upon activation the (3) 4D Batteries were at 12.4v. Within a couple of hours, in full sunlight, brought up the voltage to 13.7 volts nicely. I then disconnected from the system using a switch I installed, started the engine and continued to charge the bat. The voltage got to 14v, I then shut off the engine and switched on the solar panels again. There are LEDs on the individual solar panels that indicate voltage present, they were now blinking when they were on full before. Is that correct should they be blinking? If that is correct wouldn't that mean that to control the current flow to avoid over charging the batteries the output of the panels are being shunted to ground by the CC-4000? (in fact I disconnected and they went on solid again) I then turned on some nav/com equipment and brought the voltage down to 13 and they stopped blinking and were on full again. That would be a pretty bad design, or do I have a faulty controller? I think the controller is crap, but I just need it for bat. maintenance. I'm a little concerned that by sinking the current to ground in order to pulse the bat. it will be putting strain on the solar panels. Specifically the interface between the wire and the substrate. As an EEE I would not design a circuit like this, open it up to the bat. to pulse not shunt to ground. Anyway just wanted some other opin. I have send an email to the manufacture, it may just be bad. I'm also looking into the MPPT NC 25A-12, found one for $95. http://www.solarseller.com/flexcharge_wind_hydro_solar_charge_controllers.htmhttp://www.solarseller.com/flexcharge_wind_hydro_solar_charge_controllers.htm

 

[sailingdog]

A lot of solar panel charge controllers "shut off" the panels by shorting them. Not a great idea, but it works and is really cheap and easy to implement. This is why solar panel charge controllers are often not recommended for use with any other type of charging source.

Be aware that the FlexCharge NC25A-12 is NOT an MPPT charge controller, and if anyone is telling you that it is, they're lying. I've written a basic primer on solar power on boats on my blog, which you can read HERE.

 

[Witzend]

Why short, rather than open the circuit. This is asinine, and as far as cost is concerned, it would not matter. Would you be concerned about the longevity of the panel with constantly shorting the output? I am! Thanks for the link. So you would recommend the BlueSky SB2000E? pricey, any others? I'm nowhere near 25 amps.
I may just design my own. After all it is just a comparator with some support circuitry.

 

[Ed Schenck]

Nice job with the blog 'Dog. Definitely a keeper for when I decide "maintenance" or something more. Thanks.

 

[dvideohd]

just a panel note...

There are new "coatings" coming for solar panels - that more light shine on the surface of the cell. This has been talked about before on site, but I just wanted to mention so that when here - that people are aware. basically, the coatings are similar in idea to how sunglasses work... so you get more sunlight on cell as the day passes - for a fixed panel size. I think that for a single panel, this can matter quite a bit - especially on a surface that moves around a lot...

I "expect" that a given panel size will cost more, but put out about 30% MORE POWER during the day... it helps...

--jerry

 

[Bob S]

jerry,

I heard/read about the new coating. Any idea when it might hit the market?

 

[Andy1237]

How are the cell attached to your bimini? Could you post a close up picture of that please.

 

[Joe A]

Shunting vs. opening circuit

I was a bit surprised by this method of regulation at first, but it does make some sense. It really isn't a cost saving measure because there is cost associated with the heat sinking of the shunt component. First of all the panel power is free and the panels are designed to deliver it so no problem there. If you open circuit the panels as a regulation method they will create a relatively large voltage that has to be dealt with. The larger voltage can increase corrosion effects or even be dangerous. Let's not forget that overvoltage can destroy a component in the controller just as easy as overcurrent. Many of the controllers are designed as shunts and if I built my own (which I wouldn't) I would do it that way.

 

[walt]

Witzend, I thought you might be an EE, I am also. Here is my take on this, could be wrong.

Shorting panels for regulation is how it was done "20 years ago" because this was a good way to do things when only bipolar transistors were available. Most newer PWM type regulators use P channel FETS now and its more of connecting or disconnecting the panel to the battery rather than shorting the panel out.

Note that solar panels are basically "constant current" so up until near the open circuit voltage, they will deliver almost the same current output. You can see a plot of voltage vs current for three temps on this spec http://lib.store.yahoo.net/lib/wind-sun/KC65T.pdf
For this particular panel (65 watt), it puts out 3.01 amps at max power but when shorted, still puts out about the same current - 3.22 amps. The charge controllers which short probably don't have a perfect short - more likely short to about .5 volts. This doesn't hurt the panel at all and the charge controller only has to deal with 3.22 amps * .5 volts = 1.6 watts. This will get warm but wont require a huge heat sink. The newer style charge controllers with P channel FETS don't have this issue at all - almost no heat dissipated.

Sailingdog, nice write up. One thing you posted in another discussion some time ago was regarding partial shading. I saw importance of this recently and took a picture. In the picture, you can see the shadow from something on my boat maybe four feet away. This is an 80 watt panel and with the shadow, I was getting 2.1 amps from the panel. When I moved the panel just a few inches to get full sun exposure, the current jumped up to 4.9 amps. I.e., the "little" shadow in the picture reduced the current output to 42% of what the panel has with no shadow.

 

[Witzend]

I talked with the ICPsolar, the manufacture of the panels/controllers, and they verified that the controller is shunting to ground, and your right Walt, this is quite an outdated design. The FET (field effect transistor for those who don't know the acronym, there are a number of versions of the device depending on the application, here is a link to learn about these devices if so inclined. http://en.wikipedia.org/wiki/Field-effect_transistor) is a much more efficient method for switching. I'm planning on adding a fourth panel, so I will need to up amp the controller anyway. My decision now is if I want to spend the bucks for a MPPT or just go with a (3) stage PWM charger. I like the efficient of converting the (E) for (I) so that when the panels are putting out > 14v, mine will do ~20v easily in full sun) it will up-amp instead of just stepping down the (E) down.

 

[Witzend]

Andy, I screwed down the PVC frame with Stainless 2.25" Screws. Drilling the holes in the Bimini tubing was a bitch, must us a center punch to mark the holes. Drill slowly or you will just burn up the bit. The PVC frame was quarter mooned notched to create better contact with the SS-tubing at the screw points. I will try to remember to take some more pics.

 

[Ron20324]

Drilling the holes in the Bimini tubing was a bitch, must us a center punch to mark the holes. Drill slowly or you will just burn up the bit.

Witz, Sailrite has a gadget you clamp on the SS tube and guides/holds your drillbit centered on the tube for easy drilling. It fits a 9/64 bit. I have one, and used it many times. At 44 bucks, it's a bit pricey but it is much like what you'd use to tap into a water pipe to drill a hole for an icemaker. You might look at one of those and see if you could adapt it. Another way is to put 5 or 6 turns of tape around the tube to hold the bit steady. A brad-point bit helps.

 

[Witzend]

Tried the tape trick, but she still walked, a good center punch did the trick. I've seen the tube driller guide before, just did not have access to one and wanted to get the job done. Was trying to figure a way of mounting without holes by making the frames the same length as the Bimini. That way there would be clear access to the sides of both the SS tube and PVC tube. Then creating some "C" clips with set screws into the SS and threaded screwes with nuts and washers through the PVC, but in the end did not trust the design to sideways forces when healed in a pounding chop.

 

[sailingdog]

Walt—

Yes, shadowing can be a big problem... but only with monocrystalline/polycrystalline panels. The thin film amorphous panels are more tolerant of shading.

As for the new nano-film coatings...AFAIK, they won't be commercially available for years.