Another solar question.

[Hermit Scott]

I was getting slow cranking after 2 or 3 weeks away so I put a 5w coleman on my boat. I have never even hooked up my shore power battery charger. My bilge pump gets worked because of leaks in the rudder shaft from above. I run my engine at least one hour on the weekends when I go. Sometimes I will skip a weekend though. I run LED interior lights and pressurized water. I check the voltages every now and then and they are fine. The engine cranks off of the two 125 AH from walmart I have in parallel. The led on the panel died, but it still shows good voltage so I am not sweating it.
The panel sits beside the cabin top winch.

 

[rardiH36]

I'm entering this thread a bit late, but I would like to opine about a couple of items that I haven't seen mentioned re the Coleman type panels:

- I had a Coleman type panel to eventually discover that the glass was not tempered and the plastic frame was too flexible to be much protection from even mild abuse. Mostly my fault since I hadn't mounted it anywhere. Just stowed it away when I went out. One day, only about about 2" high from putting it down, it slipped from my hand and hit a corner first. With only a flexible plastic frame protecting it, it twisted and the glass broke. Other types of solar panels generally are made with tempered glass and are protected by a much more rigid anodized aluminum frame.

- From what I've observed, Coleman type panels are made with an older amorphous (non crystaline) silicon technology which is the least efficient type. Hence the size of the panel is about 2x's larger for a given wattage than if made with more recent monocrystalline silicon technology. The 20W monocrystalline panel that I bought to replace the one I broke is only about 15” x 16” vs the 14” x 39” of the Coleman 20W panel.

Here is a URL to a 20w monocrystalline panel with tempered glass: http://cgi.ebay.com/20w-solar-panel...emQQptZLH_DefaultDomain_0?hash=item3efa99a0b0

Attached is a photo of where my replacement panel (not Coleman type this time) is mounted. I don't do blue water sailing, so I'm not concerned about errant waves up the stern hitting it. The panel successfully keeps my two group 27 batteries and an emergency AGM battery charged without shore power between outings. But I’m not demanding much. Other than powering the 12v stereo system I have on board, no other drain is put on the batteries.

 

[Fairwind]

Try eBay for panels and controllers. Why does your bilge pump run so much?? Sounds like your boat is sinking...

 

[rickmorel]

I've spent about 5 years total living aboard with solar power and my company did consulting. Here's things I've learned.

A good rule of thumb is your will get from 1/4 to 1/2 the wattage rating in Amp Hours per day. So a 20 Watt panel will give 5 to 10 Amp Hours per day. The higher number is for further south and/or longer days of summer.

To figure max Amp output from wattage, divide the watt rating by 18 - most panels are rated at 18 Volts and it works out right on for the manufacturer's stated Amps out.

To check a panel. Aim it at the sun on a cloudless day. Measure the open circuit voltage (panel not connected to anything but the voltmeter). You should get 17 to 21 Volts for a 12V panel. Then use an Ammeter to measure the short circuit current. That is connect the ammeter leads directly to the panel. This goes against instinct but it does not hurt the panel at all to short it out. The Amps should match the manufacturer's stated short circuit current.

I can pretty much assure you that you will cook your batteries, no matter what size, if you use more than a 10 watt panel without a regulator. Unless something brings them down, it just adds up and adds up....

We have a total of 600 Watts that handles all our needs - fridge, freezer, watermaker, TV and computers, lights, etc.

Rick