48-volt house bank. Next Gen for boats?

[mcarthur]

Part 2....

We want to spend time on European canals some of which are speed limited. Running the engine at the low RPM's to stay under the speed limit would be possible but not good for the engine. Having said that, the boat normally has a CPP, so in theory, I guess one could set the prop pitch to load the engine but not go fast, which seems like going backwards.

However, hooking up a parallel hybrid to a CPP drive line seems complicated and added a single point of failure I don't like.

Then I found out aboutBlueNav(BlueSpin Inhull, retractable electric motor for boats)which makes retractable 15KW e48 volt electrical motors that can be used to propel the boat and act as bow/stern thrusters. Ah HA!

The BlueNav retractable motors solve the hybrid problem very nicely. The boat would have two separate propulsion systems. Now, the hybrid is not going to get you anywhere fast, or a great distance on battery power, but it would work for short distances and if there is a diesel engine drive line failure in restricted waters. Since the BlueName motors can be used as thrusters you really get two uses from one motor. From looking at the boat we want, we would have to have a BlueNav motor in the bow mainly for the bow thruster function but it could be used to move the boat too. Due to the design of the stern, it seems like two BlueNav motors would have to used aft. This would provide a total of 45 KW of propulsion but the numbers I keep getting is we would need only about 5KW for no current and no wind conditions.

Three BlueNav motors would require three “holes” in the hull while a bow and stern thruster would be four “holes” in the hull. It might be a small thing, but three “holes” would be a bit more efficient.

So, go with 48 volt system to handle the batteries, lower cable size, weight and cost, while maxing out the batteries to 100KWh, not only to just stay in place for a long time without power generation, but to power a separate electric propulsion system.....

BlueSpin looks interesting, but note that it does come with complexity (360 degree turning), so is probably (?) expensive and you'd want to look at warranty for something newish like that. Rather than that, there are retrofit thruster units that you can essentially hang over the transom (and bow) and have few moving parts - this would allow you to have a fixed, non-rotating electric propulsion which should be simpler and cheaper. Of course at lower speeds you have to consider steering, but since you are going for a new build then you can cater for that in the design.
Also their system it seems to use a Kort nozzle which has its own pluses and minuses for the concept, but another minus is that you may not be (easily) able to fit a larger prop to get the best efficiency for your particular boat. Of course at really low speeds (2-4kn) it probably won't make too much difference.

Since you are still at thinking stage, I'd suggest thinking of a narrow catamaran. It has all the deck space available for solar, can fit in the canals (4.9m BOA), can have two engines widely apart for steering, and can have nice internal space (IMHO). Our lovely lady is one such that was designed for the French canal system (NOT Midi ), and we're planning on 8+kW solar with a (likely) parallel hybrid on our 2x135hp diesels. We've already changed to a 48V house bank and a small starter solar array to test things, and are designing the 12-15kW electrics which will run off the existing shaft (aka parallel hybrid). I would like to change to 48V bow thrusters and anchor winch, but given the 12v are working it may be too many BOAT bucks for now.