Winter charging with solar design question

[nestorph]

Apologies if this topic has been covered, but I did as much research as I could and still haven't gotten a clear answer. Here's my situation:
My 30' Islander is on the hard during the winter but has shore power during sailing season. I would like to install a suitable solar panel arrangement to maintain the batteries enough to provide power to the bilge pumps when necessary (I'm still tracking down some leaks that allow rainwater to enter the bilge). I have a typical two-battery arrangement with a deep charge for accessories and a starter battery. I have a "side concern" about the mounting arrangement to discourage theft, so I assume a semi-permanent mount would be best. Does anyone have a comparable setup that you would be willing to share? Pics and specs would be fantastic!
Thanks in advance...

[thomm225]

I used a 20 watt panel to charge my batteries when my boat was on the hard in 2018/19 with a Windynations PWM controller.

It worked just fine.

https://www.amazon.com/WindyNation-S...17357934&psc=1

[wyb2]

I feel like you are well into a gray area. Large batteries, small leak: no solar needed. Large leak, small batteries: get a 20 or 50w panel with a controller. Large batteries, medium leak: maybe a 10 or 20w without a controller will work.

How much snow do you get? Panels covered with snow put out next to nothing. But if they are installed at a significant angle, the snow will tend to slide off, largely solving this problem.

And of course you may find that fixing your deck leak ends up being faster/easier than figuring any of this out.

[dougweibel]

While your need may be different than what is normally considered approach sizing the same as you would for any solar install. First figure out how much energy per day you need to run the bilge pump and any other loads that may be present. Then size the panel(s) factoring in hours of daylight in your winter location, winter sun angles, and how much cloud cover you expect. Depending on typical winter weather where you are located solar conditions might be very poor and I might be budgeting to try to collect a full week of energy in a single sunny day per week. Not that you will have one sunny day and six overcast - you may just have extended conditions with significant overcasts where you are only capturing a fraction of the energy you could with full sun. The effect of snow has already been mentioned.

If you are needing to consider sizing the panel to to capture enough energy in frequently cloudy conditions then you also need to make sure your battery is able to store enough energy to run the bilge pump during periods of extended cloudy weather.

If the boat will be unattended and the consequence of undersizing is water damage then obviously you need to be pretty conservative. Seems like a pretty difficult sizing scenario. How much rain? How bad a leak? How much cloudy weather?

[thomm225]

So I used a 20 watt panel above with the boat on the hard which worked fine to maintain the batteries while on the hard in Winter.

Controller was a WindyNations PWM.

With the boat in the water during Winter, I leave only my old 65 watt panel hooked up to maintain the batteries (two 220 ah Golf Cart Batteries in series) with a Victron MPPT Smart Solar 75/15 Controller..

I don't use shore power.

Once a week usually I turn all power on to everything just to let the systems work a bit.

Main daily power use is from the bilge pump which is negligible. Most times it doesn't come on at all unless we have had a few days of rain

The system is rarely out of Float