Solar panel power recommendations

[stickinthemud57]

I am planning a three-night cruise and considering purchasing a flexible solar panel and charger kit. The idea is to attach the panel to my bimini top. I do not plan to leave it on the boat as a matter of course.

I have two deep-cycle marine batteries, and power demands are low on my boat. I can hand-start the kicker, all my lights are LED, there is no AC, cooking can be done on a butane hotplate or propane Magma grill. I have a couple of 50-watt Crockpot lunch warmers that will probably come into play.

For a short trip like this, a solar panel may be completely superfluous.

So, will a 100-watt unit do it for me, or should I consider something with more punch?

Feel free to recommend a system if you are so inclined.

 

[Ralph Johnstone]

I have two deep-cycle marine batteries,

How many amp hours in total ?

 

[stickinthemud57]

How many amp hours in total ?

I gave inaccurate info. I have two marine starting batteries (700 cranking amps, 140 hour reserve capacity). I do not see total amp hours information on the batteries.

 

[dlochner]

I gave inaccurate info. I have two marine starting batteries (700 cranking amps, 140 hour reserve capacity). I do not see total amp hours information on the batteries.

In reality there is not much difference between "Marine Deep Cycle" and Marine Cranking. On a 26' boat I would guess they are Group 24 batteries, which have a capacity of about 65-70 ah when new.

A 100 watt solar panel will produce about 300 watt hours a day on average. Higher quality panels will do a little better, lower quality panels will be less. This will be less if it is cloudy or overcast, maybe a little more if bright and sunny with no shadows on the panel. This is for full day exposure. That is about 25 ah. So, if your consumption is less than 25 ah a day, then you should be ok for a three day trip if you start with batteries that are fully charged and fairly new.

For a good discussion of Deep Cycle batteries, see the article below.

What is a Deep Cycle Battery? - Marine How To

Light Cycle vs. Deeper Cycle NOTE: This article deals with FLOODED marine batteries, not AGM or GEL batteries. The Problem: The problem, as I see it, is one of dishonest marketing where multiple battery types wear the same clothes (sticker) and will perform differently when

marinehowto.com

 

[stickinthemud57]

Thanks for all the responses. Very informative!

 

[Tom J]

A flexible 100W solar panel would probably work very well on your boat. You can get one with snaps that will attach to your bimini easily.

 

[dlochner]

A flexible 100W solar panel would probably work very well on your boat. You can get one with snaps that will attach to your bimini easily.

Some folks have reported using rare earth magnets. Attach them to the panel and put the other magnet below.

 

[jssailem]

Some folks have reported using rare earth magnets.

Have there been any reports of piloting error due to strange compass drift on those boats?

 

[dlochner]

They report no interference with binnacle compasses.

 

[Orbweaver]

On my H26.5 I installed a 100W panel, and had similar power needs/storage. I typically sail around 47.8°N, so not ideal solar conditions. I also had an energy monitor, with the shunt wired to show me how much power was being drawn out of the batteries. If the solar charger was putting more into the batteries than I was using, then the monitor would show zero amps being withdrawn. (yes, I could have wired in a switch and monitored the other direction also, but I didn't really care)
For MY use, the monitor would only show discharging in the early morning and later evening, unless it was overcast and then it might show a little usage. At night I was drawing typical lights, and then I ran my cpap off the batteries all night (I did turn the heater/humidifier off while on the boat). Typically, the batteries were fully charged by 10am or noon, and I stopped worrying about every little led light that was left on. In fact, the second year I pulled the 100W panel off and installed a 50W panel. Same thing, except it took until noon or 1pm to fully charge back up. My charge controller was just a PWM model.
On my new boat, I'll be installing a 50W panel.

 

[chp]

I still have my Mac 26s that I've owned for 12 years, even though I've moved to a Hunter 280. My wife and I wanted the trailorability of the Mac. As long as you're not trying to run a fridge, I found that a 40 watt panel would supply us for a week on the water. All lights are LED and we would watch movies with the laptop at night and maybe the stereo for a bit. We never used more than 10 to 30 percent on my one 100 amp hr battery. I too started with 80 watts and two batteries and found we didn't need it. The other charging system I have is the Merc outboard alternator is also hooked up. It only puts out a max of 5 amps and I'm sure it adds some power to the batteries. If you keep your life simple, you don't need much. After all we are out to enjoy life on the water not on the couch at home.