Regarding the recent question and answer on DC vs big gensets, we are just getting ready to move after sitting for six days. Genset has been run once for two hours during a wash/dry cycle in this period. Prior to warming up the engines just now battery capacity stood at 52%.
This is after fairly heavy usage of AC power (from our inverters) for two computers during the six days. One of these is a lap top, the other an Imac with a 25″ monitor and a secondary 24″ monitor. Two movies were also watched during this period (42″ plasma TV), and almost all cooking has been electric.
Posted by Steve Dashew (May 24, 2009)
May 25th, 2009 at 11:05 pm
I recently spent two weeks on board a hybrid drive 43′ ULDB, enough time to evaluate the pluses and minuses of this type of system. Great fun to have instant thrust from the motor without sound, and to have everyone think you always sail the anchor out! I’m not convinced that charging through the prop is the way to go though, and our battery size was only sufficient for about one hour under motor until the generator had to be started.
To further follow up on the generator / alternator balance question raised recently, what are your thoughts on an electric drive propulsion system for a sailing vessel in the 80-120′ size range? A typical arrangement would include two gen sets and a single propulsion engine of 350-450 hp. Under way this kind of vessel will motorsail much of the time, with the engine lightly loaded and a generator often running as well. Would this not be an ideal situation for a twin generator arrangement with generous DC battery bank and electric motor drive? When underway a single generator could handle all loads efficiently, and the DC reserve could allow your style of power usage for a day or two if desired when at anchor. Thanks,
May 26th, 2009 at 8:40 am
Richard:
Charging through the prop has two drawbacks. One is the substantial drag of the fixed prop. Second is noise, which varies with speed. We have fitted both alternators on the main shaft and on separate shafts. All have been removed after time. They did a great job charging, but the constant noise was never worth it.
The other problem is the reliability and track record of yacht diesel electric gear. A little early in the cycle for this to be serious contender for cruising to remote locations.
But when their is commercial quality gear around, it could make a lot of sense.