More than want to know about batteries and charging systems

[hectoretc]

There have been a good number of discussions on these forums about electric trolling motor applications, associated battery placement locations, battery sizes (wieght vs output return) cable sizes, solar or land based chargers and the like.

I found a somewhat complete appearing FAQ on batteries (types, charging systems, discharge and cycle rates) to answer questions that someone may still have. It's a lot of reading, but it at least appears pretty complete. http://www.windsun.com/Batteries/Battery_FAQ.htm

Also, while researching solar chargers, I found them often on sites that also offered wind generators, and started wondering if anyone has ever hung a small wind generator on their mast to accomplish the same thing (battery charging) as intended by solar panels. That thought caused me to do some additional googling in another direction.

For anyone else interested in "thinking" about this, I did find a source for small mini-wind generators that look like they could sit on a mast without tipping the boat over at: http://www.usawindgen.com/125.html ($75-$125 for 50-150 watt systems) There would obviously be some mechanical issues with getting it onto the mast-top for non-sailing charging and down for sailing (or would you need to bring it down?). Maybe it rides up the sail slot on some jdoorly conceived bracket using the main halyard? At this point this is all conceptual anyway, but dollar for watt, the wind generator seems about 1/2 (or less) as expensive as a solar panel and works 24 hrs/day sunny or cloudy as long as the wind is blowing. Just a thought for commentary or discussion. Anybody ever seen one on a moored sailboat?

[Alan]

I've seen a few on moored boats in marinas, but they were all mounted to the deck or transom.

[jdubes]

I've seen a few of these on moored boats but not on a daysailer. And when I say daysailer, I mean something under 24ish ft. I've never seen them attached to the mast. Usually they're firmly attached to the transom.

I use a small solar panel and a battery on my other sailboat to pump out the bilge when it rains. It works great, I haven't had any problems with the battery or the panel.

Jason

[jeadstx]

I don't use my solar chargers when out for a day's sail, but on the Texas 200 I had two solar panels mounted for recharging my electronics during the six days of sailing. One was mounted in the stern on top of my bed boards. It was also hooked into a small battery pack for electrical use after dark.


The other panel was mounted on my hatch cover.


Both panels are 5w. The hatch panel is a flexible one that can be rolled up when not in use.

John

[hectoretc]

Hi John,
I guess it's a silly question becuase you would have likely said otherwise if it were the case, but did you feel the panels kept up the batteries pretty well during the Texas 200? Not remembering all of the battery info from the link at the top of this thread, but it sounded like 5 watt panels would be more inline for maintaning a fully charged battery than to recharge a battery that's been moderately or heavily used. Just curious how your real life experince lines up with the message in that Battery FAQ posting.
Thanks - Scott

[jeadstx]

The panel in the stern was hooked into a battery pack I made using two rechargable 12v batteries I got from Home Depot. I think they were for a garage door opener. I didn't want a real heavy battery. The stern panel and battery were used for powering a small electric cooler. The panel alone wasn't enough to power the cooler. The panel was used to charge the battery, while at the same time the battery ran the cooler. At the end of the day I could recharge my VHF radio fairly quick.

John

[GreenLake]

Solar panels dislike being shaded. The photos show linear shadows on both panels. Those typically reduce the available output substantially.

[jeadstx]

If you are refering to my pictures, the top one was taken at the house with a large horse trailer blocking the sun. The hatch cover one was dealing with clouds when the picture was taken.

John

[GreenLake]

I was referring to the lines that are draped across which would produce a line of shadow, which, from all I hear, should affect the output of the panel out of all proportion to the simple area being shaded.

In the other picture there are some posts - if they are part of the boat and could shade part of the panel, same issue.

From what I've read, the problem is that if one cell in the panel is shaded, not only does it not add voltage to the output, but it also doesn't conduct as well, so it's resisting the currents created by the other cells in the series.

Sounds like you had things configured differently when you were actually using the panels.

[jeadstx]

Didn't even notice the lines in the hatch cover panel. That panel is a flexible fold up panel. Best one I've ever had, bought it about 5 years ago. Works well even when the sun is partially shaded by clouds.

The panel in the stern has no obstructions when sailing. The "post" is my mast support for trailering. I needed a picture and set things up while it was on the trailer in my backyard. When in use (on the Texas 200) it usually gets full exposure to the sun due to the point of sail we were on predominately. Sailing northeast on a run with the wind coming from the south to southeast. The Texas sun does its job.

John

[hectoretc]

I was referring to the lines that are draped across which would produce a line of shadow, which, from all I hear, should affect the output of the panel out of all proportion to the simple area being shaded.

Your comment is well timed with a demonstration I saw just a few days ago. Reinforced exactly what you were saying, there was a solar panel, maybe 1 foot by 3 feet set up, knocking out maybe 3-4 watts of power (as indicated on an actual power meter) and the demonstrator simply held his open hand a foot over one portion, (he couldn't have been covering even 5-10% of the panel) and the power dropped substantially over 1/2. I was amazed how much impact a rather small shadow had on the overall efficiency. They commented that you should only plan for about 5 hours of full charging ability during a day, and the demonstration reiterated how important it is to keep the panel flat, perpendicular to the sun and clean.

[GreenLake]

John, looks like actual in service conditions are good for you. I haven't considered anything even remotely as ambitious as your Texas 200, but if I ever need to charge batteries remotely, I know whose footsteps to follow. Thanks for documenting your setup.