Solar Battery Charger

[Andrew]

I'm looking for a economical means keeping a battery charged on a small sailboat (19ft) primarily to power a bilge pump while on a mooring. What is the maximum output (milliamps) an automotive battery can take that won't over charge it i.e. so that I won't have to bother with a regulator.

Any thoughts on this possiblity?
http://www.siliconsolar.com/Solar-Car-Battery-Charger-p-139.html

[amper]

From your link:

"Q: would like to recharge a 12v car battery which is used to power a few lights, which solar panel do I need to recharge the battery and do I need a charge controller?
A: First, it is always recommend that you purchase a charge controller when recharging 12v batteries unless you are only trickle charging (1-5 watts) Silicon Solar Inc carries a universal, affordable charge controller which can be used with nearly every solar panel less then 50 watts. The charge controller can be found at http://www.siliconsolar.com/shop/catalog/Solar-Charge-Controller-p-16156.html Selecting a solar panel can sometimes be difficult since it depends on the amount of power your are drawing from the battery and your isolation levels. For keeping a standard 12v battery up to charge, we recommend using our ThinFilm solar panel series or our new GridMaxx thin film solar panels. These items can be used in conjunction with the above charge controller to maintain most any 12v battery source. "

[Andrew]

So 13V x 250mA = 3.25 A
No problem, right?

[Syed]

It will be 3.25 (w) watt

[Thorne]

Like any other system, you need to look at the draw/usage to determine the input/charging requirements.

Will the bilge pump be running constantly during heavy weather, and be solely responsible to keep the boat floating? Or does it just empty out a tiny bit of water during the summer?

If the former (or similar), you'll need a full-on charging system, but may have to also run from shore power during the winter or storms. If the latter, then the cheap trickle-chargers may work just fine.

[Andrew]

It will be 3.25 (w) watt

Yep, that would have lost full credit at school.

[Andrew]

Thorne, this should be a minimal draw application. At one point I had a ~1'x2' panel with only blocking diodes, that could run a small bigle pump itself (though I never tried it with a load). It seemed to maintain a charge on a new battery in a leaky boat for a month or so but I was concerned that for longer periods I might be overcharging the battery and degrading it.

[Thorne]

Well, considering the costs of good batteries and chargers, $35 for the controller is probably a good idea...

http://www.siliconsolar.com/shop/solarimages/Solar-Charge-Controller_t.jpg

[J. Dillon]

Andrew, If all you want to do is pump your bilge , how about this item ?;)

JD

http://www.jrsupplies.com/

[Tom Lathrop]

I like Jack's idea but in a calm cove it probably won't be adequate.

Battery experts say that you can charge a battery continuously at up to 2% of its amp rating without damage. For only keeping a battery charged for bilge pump service I doubt you need anything as fancy as a controller. An inexpensive self regulating panel, which means that it has fewer cells, lower charging voltage and won't overcharge your battery should work for you. I would guess that about 10 watts (about 0.83 Amp max) should do the job unless you have a leaky boat. This has worked for many others for the same purpose.

[Andrew]

Jack - Interesting. I think there would be enough wave action where I was planning to use it. I'm leaning toward an electric solution but it would be a good failsafe option. I like the pickup tube. My low point is to narrow for a bilge pump so there's always water left. Do you have any experience with one or know someone who has?

Tom, Thanks for the confirmation. I thought I might get away with the the charger above ( http://www.siliconsolar.com/Solar-Ca...ger-p-139.html (http://www.siliconsolar.com/Solar-Car-Battery-Charger-p-139.html) )
but was looking for a warm fuzzy from you guys.

[Dave R]

For my previous boat I used a solar charger that was originally shipped in a Volkswagen. It was intended mainly to maintain a battery but it worked fine as a trickle charger. They're not very expensive and easy to find on eBay. This is the number for the first one I came across today. 220132468008

A friend put me onto this. He uses one to maintain the battery for his boat while it swings on its mooring.

They aren't weatherproof so I used an inexpensive translucent plastic tub turned upside down to keep mine in.

[Tom Lathrop]

Tom, Thanks for the confirmation. I thought I might get away with the the charger above ( http://www.siliconsolar.com/Solar-Ca...ger-p-139.html (http://www.siliconsolar.com/Solar-Car-Battery-Charger-p-139.html) )
but was looking for a warm fuzzy from you guys.

I don't think so. This little unit will only be able to maintain a battery that has minimal or no load on it. Like, say, a clock and security system in a car.

Remember, the ratings on a solar cell are generally for the panel oriented at optimum angle at the brightest time of day. I'd consider the 10 watt unit a minimum. A friend tried one of those little ones on a boat with an auto cycling pump and it drained his battery rather quickly.

[Frank Wentzel]

Another thing to note is that the charger you show is intended to be inside the car on the dash. It is not made for exposure to the weather.

As mentioned above that unit is intended only to keep a battery topped off. It does not put out enough power to recharge a battery that has any sort of a load on it. That unit will be able to put out no more than about 1 amp/hour per day, what with clouds, orientation, shadows and other power robbing issues. Your bilge pump (assuming a 10 amp draw) will use that up in 6 minutes with nothing left over for battery maintenance.

/// Frank ///

[J. Dillon]

Andrew, I talked with the owner producer of the wave action pump and she assured me the unit does the job. I'd order one for my own boat but I do have AC at the dock and a 110V automatic pump to get out rain water. I suspect the wave action pump could be overwhelmed during torrential down pours but after it is all over probably would pump out the boat dry.

Why don't you give em a call at their 800 # and talk to Joan ?
http://www.jrsupplies.com/


Good luck whatever you do.

JD