If you run your engine or generator to charge the batteries on your boat, you don’t need telling about the soaring cost of fuel. So… if someone told you about a way to get your batteries charged for free, you’d be interested, right?
Well, of course, we all know there’s really no such thing as a free lunch, but for a moderate investment in solar panels, over a period of time it starts to get near the truth. So if you could save 2 hours running a day at say 1.25 litres/hour at say 87p/litre that would save over £2.00 a day… do the sums!!!
If you live aboard your boat I guess you may need to run your engine for up to 4 hours a day if your energy consumption is anything like ours! The laptop, TV and fridge are our biggest consumers of electricity and even if you are out all day that fridge is still soaking up your precious power.
I decided to take the plunge (well not quite literally, but that’s another story) and fit 4×85 watt panels and we have been delighted with the results. The first couple of days were quite dull, but even so, the difference in engine running time required to charge our batteries was nearly halved because solar panels work on light not heat and over these last couple of gloriously sunny late September days we have seen our Smartguage reading 100% charged by midday and the only reason to run the engine to produce some hot water which just took half an hour.
I decided that my installation would incorporate two storage boxes so I created a design so that the solar panels would form the ‘lids’ of the boxes. The boxes are made out of decking, the base being basically two longitudinal bearers of sufficient height so that the deck boards screwed onto them crosswise clear the curvature of the roof. More boards form the sides with the ends cut to give the slope to the ‘roof’, this requires a bit of maths to calculate the height, which you must select so that you will get under the lowest bridge you intend to pass under! I hope that the choice of decking will produce a durable structure proportional to the quality of the decking chosen.
I chose Sunshine Solar Limited to supply the panels and ancillary equipment and have been pleased with the products and the support received from them. I chose 1205 x 545 mm 85 watt panels as it enabled me to mount them on a 1.2 m square box. Good design dictates that the panels should be as near to the battery bank as possible but unfortunately the design of my boat made this difficult so a compromise had to be made and heavier cables were specified to connect to the controller (or regulator) to minimise the voltage drop.
As I have two domestic battery banks I used a Dual Controller with a remote meter which records the amps, volts and ampere hours produced and can be set up to distribute the output in different ratios between the battery banks.
An ebook of plans for the box design is available which includes sources of the hardware required and the formula to calculate the slope, click below to download.