Special guide on how to fit solar panels on a narrowboat

A client of Thousand Suns has published a very detailed description of the installation process of our panels on his narrowboat. Here is an extract of his excellent walk through:

Rationale:
Why did we decide to fit solar panels? Basically it was a decision taken because we have had a spate of problems with our 3.5 Kva travel power / charger combination. It was time to have a second line backup. The first line of backup is to rewire the electrics to use the starter battery alternator to charge the domestic bank as well. That takes about 2 hours, is fraught with danger (playing with over 800 amps of power is always fraught with danger) and one day that poor little alternator is going to complain of overwork. It also costs a fortune in diesel as the engine has to run 4-5 hours a day.

How did we expect the solar panels to work? We want to cruise between 2 and 4 hours a day which will bring the batteries up and then have them “topped off” by the solar panels. There was never any intention, or expectation, that solar cells would replace other forms of charging. Just reduce the amount of engine running solely for charging.

(...)

Dreaming up the system:
So it's all dead simple, one or more panels, a cable, and a charge controller, just spend your money and it will generate free power for years. If only life were that simple. So I spent some time on the potential problems.What is the real day to day efficiency, nobody mentions that. Keeping them on the roof despite the vandals, thieves and muggers. False voltage levels confusing the control of the battery by alternators/chargers. Potential cable damage when you lob a few sacks of coal or half a tree trunk on the roof. Voltage drops due to the length of the cable.Losses due to the panels being flat rather that being pointed at the sun; nobody ever mentions that either.

(...)

Mistakes:
Not doing this last year, or the year before.
Buying special sealant rather than using ordinary silicone.

Conclusion:
On a summers day the panels supply most of our electrical needs between 8am and 8pm. With an engine run of 2 hours (cruising) no extra running of the engine will be needed. The system works better than I expected. Even in total overcast it produces a few amps (which covers the overhead use) although one big dark cloud did reduce it to zero for about 10 minutes.

Fitting the system was straightforward but the details, such as weatherproofing the electrics were tedious and time consuming. I will re-visit them in two weeks to see if I did a good job before fixing the cable to the roof.

Give considerable thought to fixing the panels down. Lots of people recommended various methods including various forms of bonding (it seems it is the normal method for caravans) but you will be bonding to paint which is not the strongest of substrates. Our battery monitor computer readout is now unreliable as it shows the solar charger output voltage rather than the actual voltage of the battery until it gets dark. We will have to re-learn the management of our electrics.

Mooring the boat will be more difficult. At the moment I try to find a place which has a good telephone signal, a good mobile broadband signal, line of sight for satellite TV. Now I must add free from shadows.

Thanks John. Read the whole thing there!