This is hardly the time of year to get the benefit from a solar panel, but I know you've been itching to know whether our solar panel on Herbie is proving its worth. I was just going to write that it's worse now the clocks have gone back, but then realised what a stupid statement that would be. As far as I'm aware, solar panels don't care what the time is as long as there's light.
What I can report is that on our recent cruise we kept the batteries in a much better state than we are accustomed to. Now this is not all down to the panel. I think the new LED lights have made quite a big difference. Instead of two or three fluorescent lights at 16watts each we were using three or four LED lights at 1.3watts each. That's a saving of about 89% or over a 5 hour evening, 17 amp hours.
Working on Carrie's advice that you don't need a fridge in cold weather, we switched off the fridge whilst we were stationary for a few days at Paddington. What little food and milk we needed to keep cold did very well in a plastic bag on the rear deck. The result was that all the time we were there we didn't need to run the engine. The solar panel looked after the lights, the radio, the laptop, and the water and shower pumps, even though the days were short and overcast. That alone saved us about ten quid in diesel, not to mention not having to put up with engine noise and vibration which is annoying when the boat isn't moving. That's the main reason we got a solar panel.
However, when you are cruising, you get a different problem. In the summer, when we're on the move each day we will get too much electricity! We've had a taste of this already. The combined input of the alternator and the solar panel fills up the batteries more quickly and the voltage rises until it is just reaching the point where it could be a tad too high for the good of the batteries. On summer cruises we'll reach this point fairly early on in the day. Then the battery protection gubbinses switch in and any extra power is effectively dumped. What a waste! The answer? Add another battery, so we can collect the extra. Then we can be less frugal with our power use in the evenings. I confess that I am a real power miser on the boat. Last summer we sometimes turned the fridge off overnight to save the batteries. Next summer we'll be able to leave it on and watch the telly.
The final good thing is that when the boat is left alone for long periods, the batteries won't self discharge. I went out to visit Herbie yesterday to put in a new engine thermostat and the Smartgauge showed the batteries were at 100%. That'll do them no harm at all.