Quote:
Originally Posted by sailingdog
Personally, I'm in favor of a small air cooled pebble-bed nuclear reactor rather than batteries... you never have to worry about recharging or running out of power...  |
Also cabin heating in winter. & endless hot water for showers. Don't you think you might get hassled at certain ports-of-call, tho? What with the nuclear reactor on board.
Puts New Zealand right off the itinerary.
All legitimate worries. But we already have AGM and gel cells that are sealed, and we can certainly design a lexan or polcarbonate wet cell housing that water cannot infiltrate. Then it's simply a matter of locating any vents or exposed terminals above/away from water exposure. This is not a difficult technical problem.
Rounding up or knockdowns, no more a problem than with existing battery systems. And if you got water 4' deep belowdecks, your batteries are the least of your worries.
One challenge would be modularity and transferability: there's no profit in making a different ballast cell to fit each part of the keel, or for each model of boat. So say boatmakers agreed to a standardized cell dimension, say 18"lx12"wx15"h. Builders leave cavities in their bilges or ballast forms to accept these modular cells, and they provide routing for vents and waterproof cabling.
One cell that size would supply about 1700 AH at 2.1 VDC (8-hour discharge rate). You may want six in series, or you might want 6 or 12V cells in a parallel array, which would be useful if you had to cut out a couple. Each such cell would weigh about 325 lbs: heavy, but nothing two strapping lads couldn't lift out & dolly to a hatchway.
Advantages: battery center of mass is as low as possible & right along the keel, balanced longitudinally. Boatmakers can incorporate batt weight into the performance traits of their craft, sure of their weight and location. Batts consume no additional space below, always a big deal with sailboats. Batts are secured and not prone to tipping or shifting beyond the motion of the boat. More capacity means you can coast longer times between charging, less deep-cycling so longer life, and you have a much higher charging rate off gensets or diesels. Big batteries are happy batteries. Marinas around the world could carry identical cells for swap-out.
Disadvantages: Access needs to be good. Waterproofing needs to be perfect. Hard to retrofit. Cost over existing standard-dimension cells, like T105s. Some risk during hull puncture, tho again, I'd argue that in such case, your batts are not your #1 problem.
I suppose one major disadvantage would be that few sailboats are equipped to charge such large cells using solar or wind. Self-discharge could represent a hurdle, esp. in warm climates. You'd need a generating capacity worthy of the storage: possibly impellers while underway, solar and wind at mooring. Heh -- flexible solar films are coming! Already boatbuilders are working with integrating them into decks, maybe even into sails.
Okay, flog away. I truly enjoy the critiques.
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