Connecting solar panels to batteries

JamesG161 · Apr 10, 2016

ArkadiyS said:
After searching through the forum topics, I am still unable to find the info that I am looking for. We have a flex 40W solar panel that is used primarily for charging our cellphones and a battery for our electric dinghy motor. I would also like to charge our boat batteries (2), but could not find HOW TO diagram/steps. Someone mentioned using a 9V cigarette lighter as a way to connect to both batteries, to just plug the solar battery (output from the solar panel controller). Does that make sense? Are there other ideas/options?

The maker of the panel should give you directions. I suspect most panels would be 12VDC compatible, but most likely that is what your boat batteries are. What is your battery configuration and uses on your boat?
Jim...

seadaddler · Apr 10, 2016

What type of connection from solar panel + from panel to + battery - from panel to - battery.
Nick

capta · Apr 10, 2016

I would use a secure plug such as the one pictured. 40 watts of 12 volts isn't much power but as cig lighter plugs are notoriously poor fitting and the contact can be hit or miss, I would go with a more secure connection. Don't forget to fuse the circuit.

Sumner · Apr 10, 2016

In your case since the dinghy battery might be at a way different state of charge vs. the house bank batteries I'd connect to one or the other and not both at the same time.

I have some of my panels connected with outdoor extension cord wire of an appropriate gauge for the panel's output. You can cut the wire at a length that is good and wire one cut end to the panel and the other cut end to the controller or maybe in your case past the controller to the main panel (fused). Mine are plugged in almost all of the time except when trailering, when a couple are unplugged. Then I take a lone female plug and put in on the exposed male plug to keep it from grounding on anything.

There are better plugs available that might be a better solution if the boat is in a salt water setting all of the time (mine isn't and the extension cords are cheap and hold up pretty good outside),

Sumner
=======================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Canada, Florida, Bahamas

Bill Roosa · Apr 10, 2016

What is the voltage output on your solar panel? You mentioned 9 volt lighter plug and I've never seen one of those is the reason I ask. Connecting a 9 volt panel to a 12 volt system will result in somewhat less than satisfactory performance. Expose the panel to sun and measure the open circuit voltage (Vo) with a multimeter.

Brian D · Apr 10, 2016

Read through this very nicely done article by Maine Sail

http://www.pbase.com/mainecruising/solar_panel

rardiH36 · Apr 11, 2016

For the last 6-7 years, I have been using the low $ gadget in below url. It allows one solar panel to charge two batteries. Senses the state of each battery and then directs the charge where needed. I have one 20w panel which simply keeps my two group 27 in a full state of charge when I am not at the boat ... without needing to connect to shore power ever.

http://www.ebay.com/itm/10A-Duo-Bat...086254?hash=item25b129a46e:g:Y38AAOSwEgVWRRjl

Connecting solar panels to batteries

ArkadiyS

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JamesG161

SBO Weather and Forecasting Forum Jim & John

seadaddler

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ArkadiyS

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capta

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Sumner

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Brian D

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