Solar panel - small, horizontal, winter - any output?

LittleSister

Well-known member
Joined
12 Nov 2007
Messages
18,177
Location
Me Norfolk/Suffolk border - Boat Deben & Southwold
Visit site
I would like to have a means of keeping the batteries (already charged) topped up. (Not expecting them to be charged up, as such, by this.)

If I had a small (e,g, notional 10w or 20w) panel horizontal on my hatch garage would I get any useful charge out of it during the autumn/winter, given it would never be ideally angled to the sun, and usually partially shaded by boom or sprayhood?

(Clearly a wind turbine is better suited to charging in winter conditions, but I loathe continuous hums and whines, they always look obtrusive on a small boat, and they cost substantially more.)
 

jac

Well-known member
Joined
10 Sep 2001
Messages
9,196
Location
Home Berkshire, Boat Hamble
Visit site
I would like to have a means of keeping the batteries (already charged) topped up. (Not expecting them to be charged up, as such, by this.)

If I had a small (e,g, notional 10w or 20w) panel horizontal on my hatch garage would I get any useful charge out of it during the autumn/winter, given it would never be ideally angled to the sun, and usually partially shaded by boom or sprayhood?

(Clearly a wind turbine is better suited to charging in winter conditions, but I loathe continuous hums and whines, they always look obtrusive on a small boat, and they cost substantially more.)

How long is a piece of string. It really depends on which way it will face, where the main shadows will fall and of course how sunny it is. So a panel that has a clean view to the south will produce more than one which is permanent shade.

That said, you should get enough to cope with self discharge with a little care. So do what you can to remove any shadows, e.g. Position the boom to be clear, not to the south of the panel, maybe remove the sprayhood or at least fold it. (Reduces wind age as well)

A long period of grey days in Mid December may result in some fall in charge but overall it shouldn't,t be to bad.
 

Sailingsaves

Well-known member
Joined
26 Feb 2013
Messages
2,079
Visit site
My mate with a small boat and battery (45Amp hour lead acid) has a 5W solar panel - voltage never dropped below 12.7 all winter - horizontal panel.

Just do the sums ref number of batteries make sure not sealed AGM and so forth that require low voltage charging. A 20W solar panel can be had for £30 now !
 

William_H

Well-known member
Joined
28 Jul 2003
Messages
13,794
Location
West Australia
Visit site
I might suggest either you mount the panel on top of the boom as I do. (with bungees) or also as I do lay the boom down on the coach roof to one side.
This latter after finding that constant swing of the boom despite being sheeted down wore out the wheels on the traveller car.
How much charge you will get and should you go for 20w panel? I don't know an amp meter and experience will tell. good luck olewill
 

Sailingsaves

Well-known member
Joined
26 Feb 2013
Messages
2,079
Visit site
It will face up, be partially shaded at times (swinging mooring) and, being UK winter, not very sunny!

Without knowing the number of your batteries and capacity of each one, others are not going to be able to tell you whether a 5W, 10W or 20W etc will do any good.
 
Joined
28 Feb 2011
Messages
168
Location
South Oxon Boatat Wicormarine
yahoo.co.uk
I have a 25w sat horizontally on top of boom which keeps 210amp of batteries fully charged all the time during winter and allows me to use the boat regularly with careful use of electrics including heater, I rarely find the need to run engine. Much depends on how much you wish to draw, with modest size battery in good condition 10w would be enough for horizontal panel during winter.
 

charles_reed

Active member
Joined
29 Jun 2001
Messages
10,413
Location
Home Shropshire 6/12; boat Greece 6/12
Visit site
The usual rule-of-thumb, for 52N, to combat self-discharge is 5 watts minimum for every 50 AH of battery capacity.
Assuming the boat is out of the water and stationary, angle the PV panels @ 20 degrees, facing S.
You will need a controller to prevent overcharging, especially if the batteries are not open lead-acid. set the float for between 13.5 and 14.0 volts.
I wouldn't suggest going to the expense of an MPPT controller.

Hope that helps.
 

JumbleDuck

Well-known member
Joined
8 Aug 2013
Messages
24,167
Location
SW Scotland
Visit site
I have 2 x 50W on the coachroof and they keep 120Ah of domestic batteries plus 40Ah of engine battery brimming with electrochemical enthusiasm through dreich Scottish winters. In summer I can get 4A out of them; on a cloudy but bright winters day 400mA or so. Not enough to use much, but fine for maintenance.
 
Top