Solar Charge Controller and Battery Hookup

[sailtobike]

Hi All,

We just purchased a powerfilm 21 W panel with a 4.5 amp Morningstar charge controller to charge our batteries on our Beneteau First 305. We have two group 31 AGM batteries ( 105 amp hr each) under the galley which are attached to a AB battery switch. The AC battery charger is located in the head locker and has four wires ( 2 red, 2 black) which I assume go out to the switch/batteries.

I was hoping I could tie the solar panel charge controller directly into the battery wires coming off the AC charger instead of running new wires from the controller ( in head locker) to each battery. So I have several questions. Do the four wires off the AC charger go directly to the batteries or do they go to the AB switch? If they go to the switch, can I tie the controller into them? I only have one panel and one controller, so my understanding is I can not tie into both batteries separately. Is this the case or does the "both" setting on the AB switch mean the batteries are in parallel which would allow me to to tie into one set of wires from the AC charger and charge the batteries together? Or heck, should I just be safe and tie the controller wires into the switch or batteries directly?

Thanks for your help!
Sunfishlee

[mitiempo]

Best to follow the wires to see where they go. Your charger output probably goes to the batteries direct otherwise it would not charge when the main switch was off, as when you leave the boat. Most chargers have one ground (black) and multiple positive output capability. The ground connections are common so only one is required.

I would run the solar controller output direct to the batteries.

[kd3pc]

whilst a noble quest, the panel you have may be a bit small to do what you want.

Never assume that the charger (or any electric device is correctly installed), i.e. - where they go and where they should go are entirely different things.

You should draw out on paper the batteries, any switches, AB switches, inverters and chargers. At that point you can make some good decisions as to where best to insert the panel controller

The sunguard gear may or may not be marine rated, so please be careful where you place it, the front of it usually gives an indication where the cables go...to the battery you hope to charge/keep charged.

[tomperanteau]

I may agree with kd3pc. You'd be surprised at how quickly your amp hours add up. Recently when I started to design a solar panel setup for my boat, I put together a spreadsheet to calculate what is needed. It takes into account the average daily sunshine, inefficiency of some of your appliances running through an inverter, daily usage of appliances, and a few other things. Then it calculates how many amp/watt hours of energy your panels will put out and tells you whether you have a deficit or a reserve of power.

You really need to plan ahead. If you have a refrigeration system you have to calculate the efficiency and should log real-world usage. Your laptops can be a real drain, too. A coffee maker, although takes a LOT of power (900+ watts) and you would think would be a big drain, doesn't really drain all that much because it is used infrequently. Again, you'll be surprised where all your power goes when you calculate it out.

[sailtobike]

Thanks for all your replies. Our First 305 is a racer cruiser with minimal amp hr usage as we only take off for a weekend. We pretty must just use the chart plotter, VHF, knot meter, fresh water pump, scirocco fan and LED cabin lights for night. I've done the amp/hr use and it is small. We just wanted an easy to use and move solar panel like the power film to top off the batteries.


I think I will go with hooking the solar charge controller up to one battery directly since they are not in parallel and bypass the switch for now. That way I can leave the boat without having the switch on. I know that will create a differential voltage between the batteries, but I pretty much use them separately anyway, so I don't think it will matter much. If I ever get to using the house batteries for more amp hrs, I can always get a starter battery and parallel the two house batteries to the solar panel. I know I could buy a duo solar charge controller now, but I did not want to invest that much yet.

thanks again,
Sunfishlee

[mdbee]

I assume the small panel is to just keep your batteries maintained while sitting? Which controller did you buy?

Morningstar recommended this controller for my 2 battery setup:Morningstar Corporation » SunSaver Duo

Although not a MPPT controller, it does what I need, maintaining my batteries while sitting.

It has multiple ways to set up your charging parameters. It will automatically charge both batteries without having to switch anything but it does need to be connected to both batteries. It also offers 4 charging cycles.

[tomperanteau]

I looked up your Powerfilm 21 and noted that it is going for around $260. That comes out to over $12 a watt, which is pretty high. Just my thoughts.

Earlier in the week I bought a three-panel 45 watt setup with charge controller that ran me $3.78 a watt including cables and controller. I just hooked it up to test it on my patio, and it seems to be working well. I'll be installing it on the boat this week and will blog about it and post a link.

[tomperanteau]

Originally Posted by mdbee

Morningstar recommended this controller for my 2 battery setup:Morningstar Corporation » SunSaver Duo

I like that controller. Reasonably priced and versatile. Good capacity for expansion, too.

[tomperanteau]

Here is the kit I bought:

Sailing Vessel Footprints » Blog Archive » Testing the Solar Panels for the Sailboat

[sailtobike]

I agree the powerfilm solar panel was expensive...but it only weighs a couple pounds and sits on top of the bimini out of the way. It has super nice and easy connectors and accessories. I can take it down, roll it up, stow it or take it home to use somewhere else whenever I want. It was all about weight and convenience.


Thanks again,
Sunfishlee