When I purchased ‘Elijah’ (ex – Safari Blue), I did so knowing that she was in need of some attention, and had been modified in the past. Some of those modifications I really like and had been well executed, but others left something to be desired. One of my first tasks was to rip out almost all of the DC wiring. The AC had been installed professionally some years previous and looked to be in pretty good condition. The DC side however was far from good. I have never seen more connector blocks, insulation tape and miss matched cable in my life….
Fundamentally the Blue 2 is a pretty simple boat. Each hull has a fresh water pump, an electric bilge pump, ans a small number of lights. Add nav lights, Nav systems and the lights in the saloon and that’s about it. It really isn’t very complicated, which is more than can be said for the wiring.
Power is supplied as standard by 2x engine start batteries and a single 210A/hr house bank in the Port hull. When I disconnected these for a while, one of the house batteries rapidly fell to around 8 volts – so was declared DOA. The second holds charge but has not yet been fully tested – I will reserve judgement, but since it does not match anything else, it will be coming out anyway.
By default, distribution is handled by a Beneteau touch sensitive switch panel with internal glass fuses. Primary battery connections are very simple via manual battery isolators, but there is no real cross engine connectivity and the house bank is charged only from the Port engine – this had to go.
The new system provides primary alternator feed from each engine to it’s respective start battery, which can now be tied together via a 3 way switch in the port hull. thus the Port engine can use Port, starboard or booth engine batteries, while the starboard engine can use starboard or both. – not perfect but better. I expect engine batteries to be generally isolated to prevent a fault in one side bringing down both batteries.
The house bank is being doubled to around 480 A/hr, split between hulls. This figure is simply a function of the numbers and types of battery I had available at the time. For a catamaran, I would normally look to move to LifePo4 batteries for higher capacity at lower weight, but in this case I happened to have a reasonable collection of 8x 240A/hr 6v traction batteries in lightly used condition. They were originally purchased for an electric conversion for my 1/2 tonner, but this has been removed and they are now surplus. Hence Elijah will inherit 4x (2x per hull) of these to make 2x 240A/hr house banks.
The house banks will be tied together via an isolation switch and 25mm cable, but will usually remain tied as a single bank. Charging of the house bank is arranged by a VSR (voltage Sensitive Relay) from each side, with primary feed going into the engine start battery. This means each engine will contribute to the house bank as soon as it’s start battery is charged, but house loads cannot drain engine batteries.
In the new world, distribution will be generally split between hulls, to reduce cable runs and voltage drop. Port systems will be supplied via the original switch panel, while starboard hull loads will be fed from a new breaker panel in the starboard hull. Additional circuit breakers will provide local protection to the Nav station, which will also be fed from the port side (closest).