Photovoltaics & BatteriesUpdated: September 17th, 2017
see the comments for individual items below
After years of reducing consumption I have finally given up and bought a new system from windandsun. I have been in contact with them since 1985 when "we" moved aboard Reine Des Flots; not wanting to run a diesel generator just to charge the batteries.
Initially we bought a Rutland wind generator but despite mooring in a windy valley it was clear that a photovoltaic panel would produce more for much the same cost and space use; plus photovoltaics have no moving parts. I remember a day in the storm of 1989 when the blades of the turbine were bent so much they hit the supporting mast, ripping two of them out and blowing them across the deck at speed; luckily we were well battened down.
During that or another windy day one of, by then, four panels, was blown onto a metal ingot rendering it all but dead; producing thence only some 0.25 amp rather than the designed 4 amps. The other three, some thirty years later are still working and have had their problems.
To the new
After much procrastinating and deliberation I initially decided on 2 panels at 250w and 2 batteries. I considered the extra power, especially during winter warranted 500 watts even though this was over twice the less than 200watts of the original 4 panels. Two batteries seemed fine.
I calculated that on a dismal winter's day I may use 12v x 3a for some 10 hr. A battery of 125Ah c20 would last three days with no charge. I thought one panel might be enough but when the first quote came through I saw £130 carriage fee. Apparently the panel(s) are transported on a pallet and the pallet is £100. So I opted for 4 panels to reduce the fee from £100 to £25 per panel.
I have also bought three charge controllers. In the past I have relied on my attentive nature and redirected or covered the panels to control battery input. This has inevitably, over thirty years resulted in some errors of over changing and shortening battery life. Equally destructive to the batteries has been overuse by running them very low, and by not charging enough when low. This wasn't a problem on the boat as there was a backup diesel generator.
The theory is that the batteries need charging more frequently to keep them working well and as the panels will live "forever" it is "cheaper" to have excess power available and not use it. Of course a real bread-head would see the option of selling the extra power that could be created but for me that's a head £~+#
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