12 volt charging

The systems on Isosceles are designed to maintain a life that is as independent as possible. I have no wish to keep my boat in a big marina, stored at great expense in a huge boat version of a car park. Apart from the fact that your views are limited to the boat next door, the cost of these places are not designed for the average person like me. 

Of course, I will not be living without all luxuries, but most of these need to be powered by the boats batteries. There are not many plugs floating around in the river to plug the boat electrics into, so I rely on batteries to power the lights, navigation equipment, fridge, radio, TV and keep my phone going. But these batteries need to be recharged each day to keep them running the things I need and the things I enjoy.

The Battery Bank

Isosceles currently has three banks of lead acid batteries, one to start the engine, one for the windlass (to pull the anchor up) and the domestic batteries. Although the domestic battery bank is currently fine, they are a few years old and have been abused more than they should have been while I had no engine as a primary battery charging source. I should be able to get another two or three years service out of them, but I'm not expecting much beyond there.

Battery capacity

Batteries will only store a certain amount of electricity, in the case of Isosceles I have a maximum capacity of 360AH (Amp Hours) of capacity, 3 x 120AH batteries. In theory if something were to need 3 amps to run then I could use that thing for 120 hours. However life is not that simple. Lead acid car type batteries, of the kind I use to store electricity on Isosceles, can only be discharged to 50% before you begin to damage the battery beyond repair. Ideally they should never go below around 70% to 75% of full charge in order to maximise the life span of the battery. That means that the 360AH of battery capacity I started off with is now 90AH of usable capacity, that 120 hours of running one thing at 3 amps I had earlier is now down to 30 hours, and if there was three things turned on it is down to 10 hours. Now 3 amps doesn't sound like a lot, but a fridge can use from 3 to 8 amps, so batteries can go down quickly.

Making electricity

Of course everything you take out of the batteries needs to be replaced. Battery charge doesn't magically reappear. There are 2 ways I can make electricity on Isosceles. One is to run the engine, which will charge the batteries and heat water in the tank. But is not ideal running a noisy & smelly diesel engine when you are in a beautiful peaceful bay. The other way of charging batteries is solar panels. I currently have a couple of small solar panels which are great for weekend and holiday use, but I'll need to expand this in a year or two when I will be on the boat full time travelling.

I did have a wind generator, and in terms of looking after the batteries it was great. I never had to worry about he batteries being even partly discharged when I went down to the boat. Unfortunately being an aft cabin boat the wind generator was right above my head when I was sleeping. Even though you couldn't hear it from the rest of the boat, when you lay directly underneath it the damn thing howled like a banshee! If I had an aft cockpit boat I'd keep a wind generator, but on Isosceles it just doesn't work.

Splitting the charge power

Schematic for the wiring of the "Sterling Pro Split R"

The (almost) finished installation of the
charge controller. 

There are many different ways of managing the charge that comes out from an engine alternator and getting it to charge more than one battery bank. On Isosceles I chose to go with a "Sterling Pro Split R", which automatically splits the charge from the alternator and sends it to where ever has the greatest need. It is true that a system of battery to battery chargers will be at least as efficient, and possibly slightly more so, but the Pro Split R is a zero volt drop device*, and it charges my batteries well so I'm happy with the choice, it also fitted in nicely with the existing wiring from the old engine with it's two alternators. One of the advantages of these modern systems is that the different batteries are automatically isolated from each other, so there is no switches or controls to remember when the engine is turned on and off.

The "always live" fuse panel is designed to run systems that I want to be maintained even when I'm not on the boat, such as the automatic bilge pumps. Due to work I can be away from the boat for weeks on end sometimes, knowing that systems like these remain functional is a definite plus to me. I think where the other wires go to from this gizmo is pretty much self explanatory** and makes for a simple system.

*A Zero volt charge splitting device does not take some of the precious charge from the alternator to run itself. When this happens it can reduce the amount of charge that gets to the batteries, and this in turn reduces the life span of the batteries because they are never fully charged.

** For the technically minded, all of the wires have circuit breakers connected at points close to the batteries in order to protect the circuits.