Lithium Batteries (for the rest of us)

[sailorboy1]

Originally Posted by skipmac

So how do you plan to address cruising range for long distance cruising?

wind

[skipmac]

Originally Posted by sailorboy1

wind

Which some people have plenty of.

[deckofficer]

Originally Posted by skipmac

So how do you plan to address cruising range for long distance cruising?

Simple, battery capacity. At the stately speed of 5 kt, a light displacement 40' cat can consume as little as 500 w-hr per mile. (32) 700 a-hr cells at a weight of 1500 lbs would be good for 140 nm.

[skipmac]

Originally Posted by deckofficer

Simple, battery capacity. At the stately speed of 5 kt, a light displacement 40' cat can consume as little as 500 w-hr per mile. (32) 700 a-hr cells at a weight of 1500 lbs would be good for 140 nm.

OK, no problem. Only 1500 lbs of batteries. Maybe I can remove about a quarter of the lead from my keel to offset the extra weight. Would take more but I'm counting the weight saved by tossing the engine and tranny as well.

For batteries I assume you're referring to LiFePO batteries? That would cost what, about a million dollars?

[T1 Terry]

Originally Posted by deckofficer

Simple, battery capacity. At the stately speed of 5 kt, a light displacement 40' cat can consume as little as 500 w-hr per mile. (32) 700 a-hr cells at a weight of 1500 lbs would be good for 140 nm.

Add a couple kW of solar and your set. Maybe a floating raft of flexible panels on a bubble wrap base dragged along behind, then roll it up and store it with the sails when in port..... might need some real good water proof joints at the panel connections but I'm sure a determined punter with an inquiring mind could get it all sorted. Maybe the dingy in tow with a fold out panel set up and a couple of pontoons to support the outer panels each side if the set up was big enough.
Maybe a cantilever set up mounted off the back of the boat that can be folded up as it's hauled back in for rough weather or cruising into a port.
I'm sure someone will come up with a brain storm idea to make self powered electric cruising a possibility.

T1 Terry

[deckofficer]

Originally Posted by skipmac

For batteries I assume you're referring to LiFePO batteries? That would cost what, about a million dollars?

More like $18K.

[T1 Terry]

Originally Posted by deckofficer

More like $18K.

Guess it depends on what voltage the 700Ah was, a 48v system would be around $16,000 for the cells but a 144v system at 700Ah would be up around the $50,000 mark for the cells, but you could cruise for quite a while on that amount of battery capacity and even the occasional bit of water skiing :lol:

T1 Terry

[Stumble]

Originally Posted by deckofficer

Simple, battery capacity. At the stately speed of 5 kt, a light displacement 40' cat can consume as little as 500 w-hr per mile. (32) 700 a-hr cells at a weight of 1500 lbs would be good for 140 nm.

If by light displacement you mean 40' carbon fiber racing machine. And by 500w/hr you mean a whole crap load more than that. You can't move a boat this big with that little power, it just isn't possible.

Your calculations assume that you are pulling down a total of 3hp to move at 5kn. I don't know where these numbers come from, but I would question the source. I own two catamarans, and an ultralight trimaran, all about half the length you are discussing, and a three hp motor on any of them wouldn't get to 5kn, let alone on a 40' cruising cat, even if it is a light displacement one.

My Corsair Sprint 750 trimaran weighs in at 1800lbs, and with a 5hp high thrust motor we can hit 7kn in dead air, into any breeze we get 5kn.

[deckofficer]

Originally Posted by Stumble

If by light displacement you mean 40' carbon fiber racing machine. And by 500w/hr you mean a whole crap load more than that. You can't move a boat this big with that little power, it just isn't possible.

Your calculations assume that you are pulling down a total of 3hp to move at 5kn. I don't know where these numbers come from, but I would question the source. I own two catamarans, and an ultralight trimaran, all about half the length you are discussing, and a three hp motor on any of them wouldn't get to 5kn, let alone on a 40' cruising cat, even if it is a light displacement one.

My Corsair Sprint 750 trimaran weighs in at 1800lbs, and with a 5hp high thrust motor we can hit 7kn in dead air, into any breeze we get 5kn.

Lets keep this an apples to apples comparison, leaving hp and gas engines out. Based on test results of the 32' Blue Planet catamaran, it runs 7 kt on 4000 watts input, output with the Torqeedo's efficiency of rpm and prop design is 2240 watts propulsion power. 4 kw-hr / 7 nm = 571 w-hr per nm. You don't think by lowering the speed to 5 kt you wouldn't lower energy consumption from 571 w-hr to 500 w-hr per mile? It would be much less, but scaled up to the weight and wetted surface of a 40' cruising cat, I think 500 w-hr per mile is an easy target to reach. My electric kayak only uses 32 w-hr per mile, giving me a 80 nm range on just 60 lbs worth of LiFePO4 cells.

Besides, a clunky MW-LINE Type C 60 passenger ferry crossed the Atlantic on just 10 kw worth of solar at a 5.5 kt average speed.
http://www.transatlantic21.org/boat/

[DeepFrz]

do, are you talking dead air motoring?

[deckofficer]

Originally Posted by DeepFrz

do, are you talking dead air motoring?

On the Blue Planet cat, yes. On the 42.5' 12 ton cat ferry, no, as it crossed the Atlantic in open ocean conditions.

Stumble was trying to compare a week kneed 5 hp gas outboard to electric, and even the little 30 lb Torqeedo 4.0 outboard is going to have twice the thrust of that gas ob.

[T1 Terry]

Originally Posted by deckofficer

Lets keep this an apples to apples comparison, leaving hp and gas engines out. Based on test results of the 32' Blue Planet catamaran, it runs 7 kt on 4000 watts input, output with the Torqeedo's efficiency of rpm and prop design is 2240 watts propulsion power. 4 kw-hr / 7 nm = 571 w-hr per nm. You don't think by lowering the speed to 5 kt you wouldn't lower energy consumption from 571 w-hr to 500 w-hr per mile? It would be much less, but scaled up to the weight and wetted surface of a 40' cruising cat, I think 500 w-hr per mile is an easy target to reach. My electric kayak only uses 32 w-hr per mile, giving me a 80 nm range on just 60 lbs worth of LiFePO4 cells.

Besides, a clunky MW-LINE Type C 60 passenger ferry crossed the Atlantic on just 10 kw worth of solar at a 5.5 kt average speed.
transatlantic21: Boat

When you consider that boat had quote: "520 Ah/C5, 48 V DC lead accumulators in each hull" imagine what the capabilities would be with lithium cells, half the required battery capacity, 1/4 the weight in batteries, much faster charging and minimal losses, maybe even 10kW of solar would be over doing it.
Or if you looked at it the other way, same capacity in batteries and solar would be half the weight in batteries and the potential to do away with any form of fuel for cooking. Now if you could adjust that roof to create different angles as required, maybe you could get some wind assistance as well.

T1 Terry

[deckofficer]

There is now a poll for LiFePO4 users with just two choices, so far 100% of who are currently using them are happy campers. If your using them, go vote in the poll.

http://www.cruisersforum.com/forums/...ml#post1390611