mvweebles
Guru
- Joined
- Mar 21, 2019
- Messages
- 7,730
- Location
- United States
- Vessel Name
- Weebles
- Vessel Make
- 1970 Willard 36 Trawler
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Impressive!!!! I extracted the schematic at the end of your article as eye candy. Having done a similar schematic for Weebles (sans 48v), I have an inkling of the amount of time, research, and effort there is to create this. Bravo!
I wish I were younger. Future looks super cool.....
Peter
View attachment 135377
re: solar, we've got 9sqm on the current cabin top, which will do about 2kW. The new solid top on the flybridge will hold another 3-4kW. Extending that over the rear deck will add another 1.5-2kW. Where we are now we get about a 4-4.2x daily kW multiplier, and in the lovely tropics it'll go up to 4.5 or so. So about 7kW of panels should give between 28-32kW/day. At an estimated 8kW propulsion from battery for 5kn of speed, that's a (sunny!) day's travel of 15-18nm on pure solar with some left for the house. Go to 4.6kn and it's 5kW for 23nm.
I seem to be at about a 3.5 - 4.0 daily multiplier midsummer Great Lakes. No tropical aspirations. So it's a tougher case.
Looking at 48v at https://www.currentconnected.com as recommended by CMS.
25 kw pack with BMS, inverter and MPPT for $9,500. Built with SOC drop ins. Hard to find fault at first glance.
See my earlier thread. Batteries are replaceable at current price of $1,600 each. Durability is the least of my concerns.Very good price but I'm not sure how those server rack batteries would hold up in a marine environment.
Jeff, rather than a sail drive you may be better off with either parallel hybrid off your existing diesel (is there one?) or if its mostly just a backup then even consider a 6kW or so outboard. Either one would mean no new holes in the hulls.
Perhaps I should maximize solar and reduce battery and do 6 kw. Off to to some measurements
I would think first step is an energy budget, then build to that with a margin for cloudy days and error; plus a factor for battery reserve-days.
On my last voyage I covered 10k miles and burned 2,200 gallons for propulsion.
Given your vessel's current great nmpg might I suggest you focus on insuring the highest level of on board systems reliability and redundancy.
That efficiency question is odd, and the overall Torqueedo history in their smaller units in comments from people online hasn't been great.
The fine print there says input power: 6kW, propulsive power 2.7kW. I've never seen it quite said that way but I suspect there shouldn't be much loss in the straight through drivetrain. If so, then it's only a 45% efficient prop ... which doesn't equate to their "58% overall efficiency" statement either.
Also the prop speed of 1130rpm is pretty low for a 12" prop. May not be a problem running at 4kn, but probably is getting up to 6kn or more.
That efficiency question is odd, and the overall Torqueedo history in their smaller units in comments from people online hasn't been great. Hard to know how prevalent any issue is, and certainly not many pod's out there to compare with.
The low prop RPM makes me think that like a lot of the other electric drive stuff currently available, they're optimizing for low speed thrust, not ability to go fast.
Edit to add: I've been using the crude metric of 10 kwh = 1 gallon diesel. I think we've established that for diesel -> DC. I think that could be used to approximate DC power to prop. Haven't really dug into it.
I'm kind of thinking I'd often run with both diesel and electric. So at my usual 7.5 knots instead of burning the usual 1.5 gph I'd throttle back to 1 gph and blend in 5 kw solar and maintain the same speed. Or 0.5 gph and 10 kw if I've got excess power.
Maybe this is off base, but it sounds feasible. I hang my dinghy on the transom, and don't want outboards back there as well, plus propping etc is a concern. I have a yanmar SD on my sailboat and like it.
I was looking at this guy more recently. Two 6.0 kw units. https://www.epropulsion.com/pod-drive/