The right way to switch to solar
QI have a 1998 Beneteau Oceanis 381 that has two 12V batteries for the house and one for the engine. Off the house batteries I run the usual array of navigational instruments, water pumps and lighting, but also have autopilot, radar and a fridge. These last three items I run rarely as I am constantly concerned about running down the house batteries. I nearly always turn off the engine battery when under lengthy sail so as to be sure I can always start the engine when required.
So, which is best to help charge the batteries when under sail: solar or wind generator? Bearing in mind the vessel model, where is best to site either option?
I have read a large amount online, which only adds to my confusion, so your help and advice in this matter would be most gratefully received. Edward Vivian
ADuncan Kent replies: Firstly, it’s very unlikely there will be any permanent connection between your house and engine batteries, more likely a diodebased split-charge device, so turning the engine switch off will make no difference.
These days solar energy seems to be making wind power less popular as it is safer, silent and requires virtually no maintenance. So, unless you plan to cruise the Caribbean or similar, the former is a better investment. It does require a plan, however, as the panels need to be mounted where they won’t be shaded. The most successful installations on monohulls are usually when mounted on a purpose-built cockpit arch. Failing that, on the bimini/sprayhood top or decks is fine. If fitting more than one panel, don’t connect them in series as this reduces the total charge noticeably if even a small area of any one of the panels is shaded.
The ability for solar to replace your usage depends on how you set things up. It’s always best to carry out a survey of this prior to installing further batteries or chargers, as there are many ways to reduce your consumption, thereby keeping charge requirements to a minimum. Instrumentation and lighting use much less power these days, but the killer device will be your fridge, many of which can consume up to 50Ah per day in the summer.
Fit a voltmeter, or better still a battery monitor, and don’t let your batteries drop below 12.2V before charging. You could also connect the fridge through a voltagesensed relay that will disconnect it at a pre-set low voltage level.