Solar Panel Question

[sogood]

As part of the upgrade on my Wellcraft, I've installed a solar panel, with regulator. I'd like to have the option of using the panel to top up either the leisure battery or the start battery. So, can I put a battery selector switch on the feed from the panel to the batteries. Just like the on/off 1/2/both switches that's already on the boat.

​My thinking is then I can select which battery is to be charged/topped up. The switch is only a single pole type, with terminals to connect the positive feed through it, so must I link the negative terminals of both batteries together? And can I presume that the voltage regulator will deal with the charge coming from the alternator while the engine is running, or should I isolate the solar panel feed to the batteries when underway. Another good reason for having the switch!

​My other option was to have alligator clips on the supply from the panel and just clip them onto whichever battery I want to feed the supply to. Any thoughts welcome.

 

[dennis461]

Based on my solar panel install on boat and backyard shed and house I'll offer some advice.

1. Alligator clips will get rusty real quick, and may disconnect when your craft bumps into the dock or hits a wake.
2. It is not a good idea to 'switch' the battery input to a solar panel controller, most come with instructions to ensure the battery is connected first. This has to do with the internal electronics wherein the electronic brain must be ON before any loads or panels are connected.
3. My boat install with single panel, single battery, and inexpensive controller is constantly connected and has not failed with the alternator supplying current to the system. And again, my setup has the B+ directly connected through fuses to the solar controller, regardless of any key switch or battery disconnect. Some people may think this is not a good idea, conventional thinking is you use the big red switch to disconnect the battery power from the boat wiring.

 

[bruceb58]

So how big is this panel?

You don't need to isolate it when the engine is running.

Personally, I always use an ACR on all my boats. I would use an ACR for a solar panel as well to combine the two batteries together. Just have to make sure the ACR itself doesn't draw more current than the solar panel is providing.

 

[sogood]

Thanks for the input. The panel is rated at 30 watt and I was going to use a Perko switch, like the current battery switch. It makes before it breaks. I imagined that if the controller is doing its job then it would be ok to have the panel connected when the engine is running. Thanks for the confirmation. FWIW the panel also has a " Load on/ off switch" . Thanks again.

 

[bruceb58]

Just so you know, a 30W panel is pretty small. You will be lucky to get 1.5A out of it. Don't rely on it to do much more than just keeping a fully charged battery from discharging.

 

[Scott Danforth]

Just so you know, a 30W panel is pretty small. You will be lucky to get 1.5A out of it. Don't rely on it to do much more than just keeping a fully charged battery from discharging.

and that is with the boat stationary and the panel perpendicular to the sun's rays.

I wouldnt bother with a solar panel below 250 watts myself as a 30w will do nothing except keep a battery topped off.

 

[sogood]

Thanks for the responses. I know the panel won't do a whole lot more than keep the battery topped off. It's more intended to prevent it from discharging too much. It's an expandable system so I have the option of adding to it over time if needed.
It's easier to mount two small sized panels rather than one larger one on the boat given the limitations on places to actually locate them. Thanks again.

 

[Scott Danforth]

agreed it is easier to mount small panels, however from knowing what I know about solar panels, especially on a boat, unless you have a really large array of them, not worth the effort or expense for what you get in return. the panels should be on adjustable mounts so you can make the best use of the suns power

 

[sogood]

agreed it is easier to mount small panels, however from knowing what I know about solar panels, especially on a boat, unless you have a really large array of them, not worth the effort or expense for what you get in return. the panels should be on adjustable mounts so you can make the best use of the suns power

​Agree with this. But back to my original question re; the Perko switch. Should I link the negative terminals on the batteries together, as there would only be a positive feed passing through the switch? I can run the negative straight to one battery and then daisy chain it to the other battery, correct?

 

[bruceb58]

Yes, negatives all get tied together.

 

[Scott Danforth]

the perko switch is severe over-kill. you shouldnt need it.

tie the grounds together, the ACR should take care of the rest.

with a 30 watt panel, a simple 5 amp micro toggle switch would be all that is needed.

or hook a cigarette lighter chord end to the panel and plug it into a cigarette lighter socket

 

[mike_i]

I agree 100%, I've built PV systems. Not to burst your bubble but I wouldn't spend the time or money since the return will be negligible.

agreed it is easier to mount small panels, however from knowing what I know about solar panels, especially on a boat, unless you have a really large array of them, not worth the effort or expense for what you get in return. the panels should be on adjustable mounts so you can make the best use of the suns power