Solar Panel - Best Method of Connection?

[Ronald_M]

Hi all.

My boat's electrical system is modest: A single 85 amp/hr battery, connected, via a 16amp fuse and an isolator, to a small switch panel. This panel has a number of individually fused and switched outputs. From here I can select cabin lights, nav lights, log & depth or a couple of 12v "cigar-lighter" sockets for powering accessories. Battery charging will be provided by either the 3amp(max) rectified output from my Honda outboard's "lighting coil", or by a small 7 watt solar-panel. As this panel is so small, it is not necessary to regulate its output.

My question is how best to connect these two charging sources. Is it appropriate to fit each with a (fused) 12v "cigar-lighter" plug and charge the battery via the corresponding socket, or is it more effective/better practice to connect them to a point nearer to the battery, ie immediately "downstream" of the battery's main fuse?

All suggestions will be gratefully received!

Ron.

 

[simonfraser]

the fuse protects the wire, so as long as you have a fuse at the battery end you can use the solar panel to charge the battery via the plug in solar panel, a simple and sound idea.

make sure the connections are sound as a small resistance in the wiring system will reduce the small charge into the battery significantly.

presumably the switch panel does not have any fancy lights that need to be on when the solar panel is charging, else you might take as much out as you put back in . . . .

during the winter it's best to mount the panel near vertical pointing south, of course ! assuming you are in the northern hemisphere

 

[lw395]

Make sure there is a diode in the output of the solar panel.
Don't connect the alternator to the solar panel with the battery disconnected. I would wire the panel, via a diode, as directly to the battery as possible.
The battery should absorb the 'spikey' output of the generator, not the panel.
HTH

 

[VicS]

My situation is similar to yours in as much that I have a rectified output from an outboard and a small solar panel

My outboard feeds in via a fuse in the main disribution panel. The panel incorporates the main (double pole) isolator. There are some shortcomings here, one of which is that the outboard can feed the boats systems without closing the main isolator to connect the battery. The high voltage that the unregualted output a previoius outboard produced damaged my Autohelm when I forgot to connect the battery once. I have half a mind to use the second pole of the isolator to swtich the outboard into the circuit rather than use it to isolate the negative, but I'll probably never get round to altering it.

My solar panel is permanently connected to the battery, via a fuse. by means of a couple of extra terminals screwed into the battery posts (just made out of a couple or small brass bolts and a few nuts and washers)

I suppose I have to admit that my main battery connections are made with crocodile clips that fit the posts. They have stood the test of time, like 29 years, so I am not seriously thinking of changing them. I always slip one off when leaving the boat!

I hope you can follow that and that it might be helpful.

If it is of any interest click the thubnail to see a diagram of my switch panel. As you will see it includes some fancy switching for the nav lights that prevent an illegal combination being used

<span style="color:white"> ......................................... </span>

 

[swampthing]

I dont at all like lighter sockets. You think there pluged in but some times theres no conection and you have to give it a lil wiggle, not ideal for a long term device like a solar. Use a proper 2 pin DC plug or even an RF jack plug for miliamperes like youre talking here.

 

[Ronald_M]

Thanks for all the advice, folks.

It seems to me that I really should do a proper job, ie wire my charging sources, via fuses and proper plugs, direct to the battery.

Maybe "short-cuts" can sometimes result in "short-circuits"!

Ron.

 

[pappaecho]

Echo - dont use cigar plugs and sockets even marine ones they dont make good contact. Maplin do some excellent gold plated terminals which take banana plugs, spade connectors, and even at a pinch bare wires, and they make good contact!
You need to fit a cheap diode to prevent reverse flow of current at night - called a "blocking diode". Maplin do them for pence

 

[VicS]

[ QUOTE ]
You need to fit a cheap diode to prevent reverse flow of current at night

[/ QUOTE ] But not if the panel is already fitted with one. A solar panel that has been supplied for battery charging will most likely have one either incorporated in it or encapsulated in the lead.