Monday, September 29, 2014

Electric boogaloo

The electric engine is more of a challenge than I thought it would be. The boat is intended to be an offshore cruiser, and our intention of making short trips down the coast is inconvenient with this motor system. Obviously the simple answer to this is: change our expectations. That would be... inconvenient though, because there are friends and family along the east coast that we look forward to visiting. Perhaps some background is in order.

Daniel, the Previous Owner, appears to be an excellent sailor and has made several long passages (1,000+ miles) with this boat, at least one of them with the electric motor. We are amateur sailors, and intend to do coastal cruising for at least the next 6-12 months.

Daniel had a diesel engine in the boat. That engine was old, and needed major repairs, to the point where replacement was probably the better option. Since he was replacing the engine anyway, he looked at alternatives that would have less maintenance and chance of failure. An electric motor fit that to a T, and was even a little less expensive than a new engine. So the engine got yanked out, the diesel tanks removed and replaced with batteries, and the new system installed. About 2 years go by, and we buy the boat.

The engine compartment is now wide open, with plenty of space to access everything, even including a water tank and a big inverter. And we never go in there to work on the motor! The battery bank is 8 AGM 12 volt 100AH batteries, in series-parallel to make a bank of 48v 200AH. Each battery is about 60 pounds, so that's roughly 500 pounds of batteries. The propeller and shaft are the same as before. The motor is a 10kW model, so it can put out about 200 amps at 48v. Of course, taking that much power drains the batteries incredibly quickly, and heats them up dramatically, so we haven't gone up anywhere near that level.

The long and the short of this is that we can motor at 2 knots for 8 hours (ish), and at 4 knots for 1 hour (ish). Which means we can motor in and out of harbor, but that's about it. Not a problem if you're making an offshore passage to a main destination, but not convenient for sailing for the day and finding a new anchorage every night. Out at sea there isn't a problem with the currents when the wind dies, but near land there are rocks and corals and other scary things to bang into.

We aren't thrilled with the electric motor.

One option is to replace it with a diesel engine, but that is really expensive ($5,000 - $10,000 anyone?) and undoes all the work that has been done to get the current system in place. Another option is to install a bigger, more permanent, diesel generator (we have a small gasoline one now) that can run the motor directly as well as charge the batteries faster. Another option is to buy an outboard motor and mount it on the stern of the boat and use that for longer distance motoring. And, of course, one option is to not change anything except ourselves and our expectations.

We're not sure what we'll do yet, since everything except the as-is option is pretty expensive.

I would like to get the wind turbine set up as soon as possible, since that will charge the motor batteries. That is a whole different topic, which I have only barely begun thinking about. I'd really like to be able to just add the turbine, and not use any bigger, costlier generator than what we have now.


  1. I feel your pain...

    Having had the same motor as you have I know exactly what you're experiencing.

    A few bits of advice... Regen is your friend, adopt the mantra of "Sail more motor less.", and keep in mind that Jerome FitzGerald makes more sense than not.

    Stick with it and it will all work out.

  2. Charging by wind sounds fantastic, I didn't know that was an option. Get it. Otherwise I'd assumed you guys would get a diesel generator: maybe spendy (although really how bad in the scheme of boat life and not owning cars?) but solves the problem and you only use as much fuel as needed. For whatever that's worth; I live on land. I remain mostly ignorant of maritime shenanigans.