solar power trickle charge

bmcald · #1 (**permalink**) 01-28-2003

Does anyone know the requirements for using a solar panel to keep a starting battery fully charged? I can''t find any kits that have it all. It looks like I would need the solar panel plus an inverter and auto shut off and other stuff that I don''t understand.

Stede · #2 (**permalink**) 01-28-2003

BMCald, I''ve never done all the math or calculated out an ideal system for recharging my boat battery, but I do have a system that works well for me.I have a 1 x 2 ft solar panel that I keep on the cabin top when at dock.I also have a small regulator that was sized for the panel.On a good sunny day,the panel provides about 3-4amps.This seems sufficient to keep the battery charged up,but not enough to overcharge.I''ve never had battery problems starting the engine,and my batteries are several years old.The West Marine advisor has some good information on sizing a system for your battery,etc.I think altogether I have about $175 in my system.

dargiem · #3 (**permalink**) 01-28-2003

Last spring I bought a 10 watt panel that I just tie over my sail cover when I leave after the weekend. I run the wire between the hatch boards and hatch cover and plug it into a lighter outlet. I bought the "male" end of the lighter socket at Radio Shack and just soldered it on. I turn the battery switch to both and sadely leave for another week at work. So far, this has worked perfect.
I did do some reasearch before buying the unit. What I have found out (I''ll try and make a long story a little shorter) is that a liquid cell battery looses ~.2V/day without any draw. If it is left more than a week or so, throw in a bildge pump or so, well, you can do the math. Also, battery health is effected by periods of inactivity. In warm weather, in just after ~2 weeks a "crystallization" of the acid takes place, and if left long enough, will short out the plates. When you charge it, you reverse the chemical reaction. Also, if the solar cell is 10 watts (@~16V) you don''t need a regulator. From what I can find out, this approach should make the batteries last 2-3 times longer than letting them sit for the week and then charging them with the engine during the weekend. Also, it appears better to store your batteries outside in the winter and slow charge them about once/month.

We''ll see!

Mike in Noank

Stan S · #4 (**permalink**) 01-28-2003

You may want to review Don Casey''s articles on this-- very informative. My approach is similar to the 2 previous respones.

I have a rigid 11watt for my house battery that does go thru a regulator. Have had for several months and working great. Permantly installed on the stern lazzerete.

This past week-end I added a flexible 5 watt for the starting battery. No regulator and I also just tie over the sail cover and run wire thru the hatch boards.

Both panels are US Solar and purchased from Sailnet.

bmcald · #5 (**permalink**) 01-28-2003

So all that''s really needed is a 5-10W solar panel, and wire directly to the battery terminals? Don''t understand how the cigarette lighter plug in works, but like that for less messing around needed. My electric panel does have a cigarette lighter outlet that I use for a Megalight.

I just have one battery, used for starting the engine as well as house needs, which is a vhf, compass light and gps. All those are used from time to time. No electric bilge pump. Ran for a little better than 2 months without losing power. The diesel engine kept it charged up. But I''d like to start learning about solar, and this seems a good place to start.

Nereus32 · #6 (**permalink**) 01-28-2003

Check out ICP Global product. They will have a complete set up for just what you need for minimal investment. Find them at http://www.icpglobal.com/

dargiem · #7 (**permalink**) 01-29-2003

Re; the cigarette lighter plug. All you need to do is buy the end(male)(can purchase at Radio Shack) that goes into the lighter receptacle(female) on your panel. Solder the male adaptor to the end of the leads on the solar panel..WATCH THE POLIARITY!!!SOLAR PANEL AND BOAT NEED TO BE THE SAME!! As long as your battery switch is closed you will "back feed" your battery through the cigarette lighter.
I just un-plug and stow my panel for the weekend.

Mike in Noank

bantrybayboston · #8 (**permalink**) 01-29-2003

Sounds like a great idea, I think I might try it. I have one question though. What does a "solar regulator" (found on sailnet) do? Does it prevent over charging of the batteries?

bmcald · #9 (**permalink**) 01-29-2003

How do you test for polarity?

Thanks!

GordMay · #10 (**permalink**) 01-29-2003

Bruce:
To test polarity:
1. Connect negative lead on voltmeter (16VDC Scale) to an electrical ground.
2. Touch positive lead to Center Terminal of Lighter Socket. Meter should read +12VDC. If so, centre is Positive, outside shel is negative.
3. If not (above), Touch Positive Lead to Outside Shell. If reads +12VDC, outside is positive.
4. Connect Solar Cell output to male socket to match above results.
Regards