Boat Power Sources

After reading the yacht-owner’s bible (Nigel Calder’s ‘Boatowner’s Mechanical and Electrical Manual’, published by Adlard Coles Nautical) we had a serious rethink about our power sources. Eventually we will be looking to install solar panels but in the short term we had to make an educated guess at what our daily power consumption would be and put that within the context of buying new batteries and battery charger. Both needed replacing so starting from the drawing board we had to work out what our power consumption would be whilst afloat.


Eventually we decided to increase our house battery source from 300amp to 405amp, made up of three 135amp batteries. This meant an increase in physical space for our batteries as the old battery bank would only house two of the three new batteries. One of these was placed under the nav table in a cupboard previously used to store random objects, so the space wouldn’t be compromised too much and it’s only a metre away from the other batteries.


BTM1 Shunt

BTM1 Shunt


Rather him than me

Rather him than me


We spent weeks looking into battery chargers. As with many things the more we learnt the more confusing the subject became. Chat forums became useful places to pick up tips and opinions and most suppliers of battery chargers were forthcoming in their assistance too. Sending out blanket emails to suppliers is a very quick way of getting back multiple replies to a single question! We decided on a Mastervolt IVO Smart 12/40-3 charger in the end (later learning that Mastervolt is Oyster’s prefered charger anyway), which would charge up to 500amps efficiently without damage to the battery bank. It also satisfied the basic charging equation which we won’t even begin to go into here. Buy a copy of Calder’s manual, he explains it a lot better than we could.


launch-powermonitorTo accompany our new charger we treated ourselves to a Mastervolt battery monitor (the BTM-I), which tells us how many amps we are pulling, what the expected lifetime of the batteries is left (in days and hours), as well as a basic indication of how much the batteries need to be charged. This was an expensive bit of kit but gives us peace of mind as we are able to constantly monitor our batteries when ever we need without having to pull up floorboards.


The image on the right shows the new dash with the BTM 1 display. On the top right of the dash is a new cigarette lighter socket (for charging mobile phones, as illustrated) and at the bottom you can see the four switches for the speaker configuration (see the Stereo section for more info on this). The bilge pump switch has been moved to the top left of the dash.





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