--- In [email protected], Nigel Stanley <nigel.stan...@...> wrote: > > I've always suspected that megapulse was snake oil. > > But is there any way for those of us whose boats are unattended for > long stretches to prolong battery life? > > Does a solar panel make a difference? > > If so what's the minimum capacity? > > How soon would it pay for itself? > > Is there a particular charger type that can do some good on say the > occasional afternoon or overnight visit and charging session? Any > recommended purchases? > > > > -- > Nigel Stanley >
We come back to the fact that the last 10 to 20% of charge takes an inordinate amount of time so putting a charger, however large, on for an afternoon now and again is not likely to make much difference. The trick is to get the 12 hours or so needed to put that last few percent back into the batteries applied as quickly as possible. Without a shoreleine I am afraid it is either wind or solar. Wind is available 24/7 as long as the wind is blowing where as solar may only be available for perhaps 6 hours in winter. However to get the quoted output from a wind turbine requires a very strong wind and with winds much under 10mph the output is not impressive at all. Turbines also tend to be noisy and if mounted on the boat cause annoying vibrations. They are also difficult to stow when cruising. For optimum output the solar panel needs to be angle towards the sun which implies constant adjustment throughout the day so many people accept less output and mount the horizontally but this implies a larger panel to achieve a given output. As far as I am concerned the offerings from the likes of Maplin are toys, especially the "plug into the cigar lighter socket" type. I would not fit anything less than 60 watts for battery maintenance and recharging between cruises purposes and it needs coupling with the most efficient controller you can get. Mine will do an automatic equalisation charge every 30 days. For livaboards I doubt solar would be economic for winter use unless they use a gas fridge or no fridge at all but for a "holiday" boat they will ensure the batteries are charged up between cruises so are not left with ever hardening sulphate. I do not think you should just be thinking about payback time because it is very convenient to come to a boat with well charged batteries and not worry about getting then charged up before going home again. It is also nice to know you can overnight or even weekend in the summer without running the engine or having to worry about the batteries. Having never got more than 3 years out of a battery bank (and one set was the yellow ones "guaranteed" for four years) I fitted my 65 watt panel and controller with three year old batteries showing early signs of failure. the batteries are now five years old and although I will change them this winter many people would not have any idea they are failing so would use them for even longer. Tony Brooks
