Pondering Solar Panels

Posted by Darrell Nicholson at 02:31PM - Comments: (8)

My post last week on storing batteries for winter prompted a couple comments and letters on solar panels, so I thought I'd point out some of our past articles on the topic that can be found online at www.practical-sailor.com. It is a timely project for me, since our upcoming project testing one of the new sonic-pulse antifouling devices will require a solar panel. According to the device's maker, Smart Antifouling, the unit draws about .08 amps, which means will want to put a small 5-watt solar panel on our Cape Dory 25 test boat, Skimmer, which typically lies on a mooring.

Several readers said they used dedicated trickle chargers to maintain a healthy charge during winter storage, and this will work fine in places that don't see a lot of snow, ice, or overcast days. The makers typically provide guidance on finding the right size trickle charger for your battery bank. For most sailboats, you won't need a regulator for a small 2- to 5-watt panel, but you will want one for anything higher than that.

Although these are not as effective as a “smart” three-stage charging system, we have had good results with some of the units we've tested. Keep in mind, the aim with these chargers is to offset the gradual voltage drop that occurs over time, not necessarily to replenish your battery or achieve the highest state of charge. There are several brands of these units, and although we've tested a few, we've not done a comprehensive test in several years. If there is enough interest, we can put together a broad head-to-head comparison.

Most recently, we've had good results with the SolarPulse charger on one of our smaller test powerboats. We will be evaluating one of the more interesting devices, the Batterytender, which boasts an internal charge controller. We do not recommend chargers that plug into cigarette lighters, because the connection is so unreliable. If you cut off a cigarette-lighter connector to hard-wire to the battery, you'll almost surely need to add a properly rated fuse to the positive lead, since this is usually inside the cigarette lighter plug.

We've had mixed results with flexible panels, which tend to fail after two to three years due to water intrusion, even if carefully maintained.
If you are using a larger panel for maintaining your battery in the off-season, you'll need a reliable regulator, ideally a three-stage charge regulator like the one that PS contributor and bluewater voyager Andy O'Grady used to help maintain the wet-cell 6-volt batteries on his boat. My wife and I would often leave our cruising boat, Tosca, for months with a regulated 80-watt solar panel charging our twin 6-volt T105 Trojan wet-cell batteries, but we also had friends check the voltage and electrolyte level on a monthly basis, in case the regulator failed. Because the panel was overkill for this purpose, we put it in a location that saw only a few hours of sun each day.

With regard to high-output charge controllers: Two brands have come to our attention. Contributor Joe Minick has had good experiences with his Blue Sky Technologies charge controller with multipoint power tracking technology (MPPT). Our recent report on electric boats also mentioned a new controller from Outback that is gaining traction. A couple of readers have also written us about their positive experiences using the Outback charge controller.

If you are pondering mounting options, our 2003 Solar Panel Survey delves into that topic as well as others. A few years ago, we reviewed the expensive SolarStik, a rotating and swiveling mount that maximizes output so long as you are there to tend to it. Past PS contributor Steve Dashew, who is pondering a massive system for Wind Horse, has some nice photos of a high-output solar setup. One thing I liked about our own solar-panel arrangement on Tosca was that the panels could be easily removed in storm conditions, or in ports where theft might be a problem - something to consider as you consider your own installation options.

Comments (8)

Tim L,
I suspect that your batteries are fully charged and that is why you only see charging activity on the display when there is a load.

Posted by: James F | February 26, 2012 11:52 AM    Report this comment

Tim L,
I suspect that your batteries are fully charged and that is why you only see charging activity on the display when there is a load.

Posted by: James F | February 26, 2012 11:52 AM    Report this comment

Recently installed 3 Kyocera 135 watt panels with a Blue Sky MPPT controller on our Catalina 400 in preparation for an extended cruise. I put them on a "custom" arch made locally in Hampton, VA and the whole setup both looks great and appears to be performing well. Will be happy to provide photos to anyone interested. My only question/concern is that it appears the controller display (remote) doesn't show exactly what wattage the panels are producing, only what the batteries (2 bank 4D AGM's) are accepting. If there is no load, the display shows essentially no amps to the batteries, but when I turn on a fairly high load item, it raises quickly to the mid-teens (which I think is probably a good number considering the sun angle this time of the year in Virginia). Does anyone know if this is normal? Don't get a great answer from the panel/controller distributer.
Bottom line is that I'm extremely pleased with my solar panel setup and can't wait for the 2012 cruising season on the hook!
Tim L.
Chesapeake Bay

Posted by: TIM L | January 7, 2012 7:08 AM    Report this comment

There are a lot of inexpensive MPPT controllers coming out of china these days (check ebay). I'd be interested in seeing how well these work.

Posted by: steven s | January 5, 2012 10:41 PM    Report this comment

Thanks guys. The unwanted intruder is indeed water. Hope you didn't spend too much time Googling around for the answer to that one. Wish I could blame the New Year's Eve hangover, but that was not the case. I'd be interested to see how the walk-on panels perform. One nice thing about the frame is that it can help bring air-flow under the panel to help them stay cool, and/or insulate it from the heat of the mounting surface. Cooler panels will be more efficient, to a degree -- so to speak.

Posted by: Darrell | January 5, 2012 4:16 PM    Report this comment

Typo - water intrusion was likely intended. I plan to tile my decks with Aurinco walk-on frameless panels. Fiddling with mounting brackets is silly, just install extra panels to catch different angles of sun.

Posted by: Jim G, S/V Koan 4 | January 5, 2012 3:49 PM    Report this comment

What is "solar intrusion"? This must be a very obscure term as Google is of no help in divining its meaning.

Posted by: Owen M | January 5, 2012 9:38 AM    Report this comment

As I am outfitting our Stevens 47 for an extended cruise with the family onboard, I would be interested to hear testing on larger arrays of rigid panels on top of the davits. Especially interested in successes or problems with higher voltage systems (such as the Sanyo HIT) fed into a 12 V house bank via MPPT.

Posted by: Max S | January 4, 2012 4:11 PM    Report this comment

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