Sizing a Solar Panel

natotm · May 18, 2009

The mounting location will dictate your maximum panel size but I'm sure that you have read many posts about consumption, capacity, etc. If you just need battery maintenance you don't need much. I have never heard anyone say "I have too much electricity" on a boat.

KappyKaplan_pea37 · May 18, 2009

I have a Pearson 37 with a 64W panel

Had the panel installed when I purchased the boat last summer. It's sufficient to keep all 5 of my batteries topped up, unless I'm running the refrigerator in the slip. Can't make a recommendation on vendors. My only caution is to think through the mounting as my frame bent during winter storage.

Dave D · May 18, 2009

I just ordered a solar panel/trickle charger through Northern Tool online. Specs say it can charge and maintain up to 4 batteries. Here's a link:

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200328565_200328565

It's even on sale right now, so according to my wife you HAVE to buy one!

Bob S · May 18, 2009

Lot of reading! It will really depend on how much energy you use. Weekends, weeks? try this site, I found it to be the best.

http://www.wholesalesolar.com/

KD3PC · May 18, 2009

I used a 110 watt panel from Hamilton Ferris on their curved rail mounts. Worked wonderfully and provided more than enough to keep the batteries topped up. I used their SMR regulator, but would spring for the MPPT style they now have. They did a great job of providing mounting options and parts as well.

dave

rardiH36 · May 18, 2009

For Dave D (1st paragraph) and Forum Members (2nd paragraph onward):

I will be interested to know if the solar charge controller that comes with your Northern Tool order has separate outputs for 4 batteries, so that each battery is charged independently according to its needs. I can't tell from the product description if this is a feature of the system, or its simply that 15 watts is sufficient to give 4 batteries a maintenance charge. If there are four independent 3-stage charging outputs and the quality is fine, this system indeed looks like a really good buy. (* But see below for a consideration about the solar panel....)

On this topic can forum members comment on how important independent charging to each battery is for solar? It would seem to me that if one output from the charge controller is hooked up to several batteries in parallel, and if the batteries are either different in capacity, type, or state of charge, the overall charging result might not be optimal.

I ask because I am thinking about adding a third battery to my existing two battery solar arrangement. Currently, for keeping my two house batteries maintained, I've got a small 20W panel which I've connected to two "no frills" solar charge controllers. The output from each controller feeds only one battery. Each battery is electrically isolated from the other when the battery switch is set to anything but "both". I'm not an an electrical wizard by any means, but my expectation is that (say) I spend the morning using House Bat #1 to power the stereo, but Bat #2 is not used. #1's charge controller will demand most of the current from the panel for recharging it. #2's charge controller will only see demand for maintenance charging and won't ask for much current. This set up has been working very well. Since I don't live on the boat, all DC systems generally are off (except for constant power to the bilge pumps of course). The only time I connect to shore-power is for the odd night we stay on the boat. Zincs last a long time!

* (My first solar panel had the same look as the one shown on the Northern Tool Website. It also came with a one battery charge controller. It worked fine and I think it would have lasted years. But it turns out that the glass was not tempered. My panel normally resided on the boat's port cockpit seat. I would stow it away when we went sailing. One day from a height of about two inches, the panel slipped from my hand. One corner hit first, inducing a twist force on the panel. The glass cracked. So keep in mind solar panels are durable, but fragile as well. My replacement panel has tempered glass, and being smaller in dimension is instead mounted permanently out of harm's way on the stern pulpit railing).

Dave D · May 18, 2009

Rardi,
Just got home with it. No, it does not have separate outputs. I can tell you that this unit's glass IS tempered. I'll let the post know as things progress. Guess I'll sneak out at 2 a.m. while wify is sleeping and go install it. Can't wait ALL THE WAY to this weekend!

sailingdog · May 18, 2009

MIckey—

I'd recommend you read the Solar Power on Boats primer I wrote on my blog. What size panel you will need depends on what you want the panel to do and how large your battery bank is. If you have specific questions, you should probably mention:

what size your house and starting battery banks
what your typical usage of the boat
what your basic electrical budget for the boat is.

You will probably also want something like an echo charger or battery combiner to help keep the starting bank charged while the solar panels are actively charging the house bank.

Mickey G. said:
I have a Hunter Legend 37 which has been kept in a slip with power for the past 10 years. Due to the ever increasing cost of a slip I have now decided to put my boat on a mooring this summer.

Now that I will be on a mooring I need to maintain the battery charges on all four batteries on the boat. My assumption is that a solar panel is the way to go.

Not having any idea how to start with this project I am seeking help from all the other "blow boaters" out there as to what size solar panel do I need, what other equipment to I need to purchase and what other parts, besides the solar panel do I need to purchase.

I have three wet cell batteries in the battery compartment, one for the starting of the engine on the switch one, 2 - "house" batteries on switch 2 and one battery in the bow for the windless I installed. Currently the smart battery charged on the boat will charge each on the batteries when needed.

Is there a particular vendor that you recommend?

Thanks in advance for your help.

Mickey

Chuck Creel · May 18, 2009

Bob S said:
Lot of reading! It will really depend on how much energy you use. Weekends, weeks? try this site, I found it to be the best.

http://www.wholesalesolar.com/

i have to agree with Bob on this one. I know there are many many sources for solar panels and such . However when installing mine i did some extensive reasearch and found wholesale solar not only very patient,helpfull, and very customer satisfaction oriented.

My unit is 1 eac kyocera 130WATT panel, Morningstar controller," bullet proff by the way", hooked up to a 3 battieres system.

The one panel alone puts out 7.5 amps and allows me to run my refridgeration for 2 days on the hook with out starting the engine.

The ice box is hooked directly to the controller so that if the batteries get below 12 volts it disconnects so tha the batteries arent ruined by deep discharges.

Good Luck

CAptain Charles creel
S/V jacob's Dream
H-30 1979

Sizing a Solar Panel

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