Floating on a Boat: battery power

People who know about battery power on a boat will tell you the pinnacle of performace is floating the battery charge as often as possible. Often this advice comes from an armchair. It is easy in a marina with shore power but it takes a lot of generated power. For me, for example, everytime the vessel is under main engine, the opportunity to achieve float is immediately afterwards. The alternator is 63Ah, which is twice as much as the Victron charger from the generator. 

For AGM batteries, the charging process is: bulk charging starts at current battery charge state and goes until about 26.5v, absorption goes from 26.5v to 28.4v or so and then the elusive float is when this number suddenly diminishes to around 26.5v. When you switch off the charging, the operating voltage will fall to around 25.6v. The result is 26v is generally considered to be fully charged for AGMs. Most good deep discharge AGMs can go down to 80% depth of discharge (DOD), which is 22 volts. I would not do this. The furtherest DOD I go to is 90%, 24v, which many unusefully consider to be 50% discharged (NOT DOD). Even that is low for me, because the big power consumers of battery power in boats are refrigeration and freezers, which are not always very efficient, and that suddenly takes the volts down below 23.5v, not even considering bilge pumps. I try to maintain a charge of 95 per cent.

Dominica, Portsmouth and Roseau

We anchored in Portsmouth in the North and Mėro halfway down and moored south of Roseau.

My wife thinks it is great. Nothing much happens in Portsmouth; we visited a small waterfall and swam in its pool, had an unnotable and slow lunch before trekking across orange clay and visiting a whimsical chocolate factory. The anchor held. There were a few pubs with dull conversations and advice on nothing much in particular. The highlight is Alexis, the boatman, ch16, for services. The bread was not a highlight either, nor was the jazz festival.

Less happened in Mėro and St. Joseph. There was only one functioning pub with nobody in it where my wife and Will enjoyed their dialogue with the old paint. Good holding in sand and plenty of people in the streets to talk to. Nowhere to eat.

Roseau was more interesting. We ended up with our anchor firmly tied to a steel wreck in Pringle bay before the coastguard kindly fleeced us to successfully lift it. Apparently this work is rarer but more interesting than taking ropes off propellers but less interesting than the even scarcer catching traffickers of various types. We were free by 1600hrs but took two hours to wrestle sufficient cash out of rare reluctant ATMs to pay.

An hour later we were moored by Sea Cat, ch16, at the Anchorage Hotel's moorings,  to be molested by the neighbouring power boat that  we powered off at 2100hrs, with millimeters to spare, requiring subsequent watches all night and moving to another mooring the next day.

Shopping in Roseau is limited, perpetually marred by lack of cash from under powered ATMs. Nature is difficult to monetise to buy your car. Everyone has the same leaves with no market. The most impressive feature for me was the Trafalgar Falls. They are very difficult to photograph, together. There is also at least one hot stream. You'll have to find it. 

It is also reported that geothermal power is going to replace the remaining diesel power and supply surplus to Guadaloupe and Martinique. A good plan to be tested soon. The day was however destroyed by a music cacophany at full volume, full speed and without texture at all that went on until daybreak. Time to move on to Martinique.