I hear all the hype about long life of lithium ion batteries and am very very sceptical. I run a computer company and deal with laptops and other small devices that use lithium ion batteries on an every day basis and while they are much better than ni-cad or nimh batterys, I have never seen any get close to the cycle life that is advertised. I would estimate that in real use a good laptop battery might get 600 cycles before needing to be replaced in the average laptop and I'm being generous and assuming that whoever used the laptop has actually discharged the battery every day for two years. If someone has a two year old laptop with a battery that still gives even 50% of its rated capacity I am amazed.
My second area of skepticism is on average quality of the batteries. ie.. percent of weak or defective cells in lithium ion batteries. out of every 10 batteries I deal with 1 will be bad or go bad within a month of getting it and starting to use it. I have a tablet pc that the failure rate on the batteries has been more in the neighboorhood of 85%. With these type of real world experiences you wouldn't catch me spending the kind of money it would take to put a lithium ion battery pack in a boat. I think you could double or triple the projected cost of lithium ion in planning the real world cost including failures and dead cells.
For a product that claims such high cycle life the warranty periods are pretty low also.. that sets off my bullshit detector as well. The average lead acid battery has a 18 month free replacement and pro-rated 5 year warranty with a average cycle life of 300 to 500 cycles. Most of the warranties on lithium ion batteries are at most 1 year "period" that I have seen. This with a product that advertises a cycle life of up to 2000 cycles.
I will not be an early adopter of this technology till it has some years of track record behind it, at least for what it costs now for them.
I like the look of the new oddysey batteries with the thin lead plate technology.. they have incrementally higher capacity but given the correct charging technology you can bring a battery bank up to 100% charge in about 20 minutes flat. The average battery bank for a electrically power boat is capable of accepting 500 amps of charge.. The limiting point now is that there really isn't any existing chargers and generators for the market that are capable of putting out this much current. The decrease in lifetime charging costs using an engine or generator
just my opionion
scott
--- In electricboats@
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> Search eBay for "Lithium-Ion Battery 12V 40AH".
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> Now granted...my (230AH) bank would run $6000. "Not cheap!" you say. But that's with a (reported) cycle time of 2000 cycles. I will generously credit my existing el-cheapo Walmart deep cycles batteries with 300 cycles. They cost $560 (8 x 12v). Good Trojan T-105's should be closer to 500 cycles - but would have cost $1200 (8 x 6v).
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> $4800 (equivalent cycles) is still less than $6000. And BMS + chargers will bump it further. But - I save 300lbs in weight, can distribute it better, is (maybe) safer, and get probably 20% more range/charge (no Peukert). It's also easy to keep spare cells on hand in case of failure. The form-factor is intriguing - I can see 3.2V cells spread out against my hull in a couple of flat 48V strings and saving my limited storage space for more beer...
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> We are not quite there...but so close. Being human, we tend not to factor in long-term costs very well - but maybe it's time.
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> Anyone running lithium (in a boat, not a dragster) yet? I think when (the rest of) my Wallyworlds die in another year or 2 - it's time.
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> -Keith
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