Jim,
The 250 cycles for the T-105s is based on a 5 year lifespan and the 500 cycles of Li is based on a 10 year lifespan. Realistically, I don't know that I would even get 50 deep cycles a year from my boat, but I had to pick something. The 500 cycles of Li is less than 1/4 the rated lifespan, but I don't think that the batteries will last 40 years. I haven't heard anything to make me believe that 10 years is unreasonable from the LiFePO4 prismatic cells. My experience has been that even when I take reasonable care of flooded cells, their performance starts to drop off noticably by 5 years, regardless of the cycle count. Other people may be more successful than I have been.
I did read somewhere that deeper cycles on FLA batteries don't really reduce the lifetime delivered Wh. Over simplified, the idea is that a battery that is discharged to 40% will last twice as many cycles as one discharged to 80%. Half the cycles, but twice the energy delivered in each cycle results in the same lifetime delivered Wh. There was no empirical data to back this up, and I'm guessing that the relation is not perfectly linear, but this might be true within 10 or 20%.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "luv2bsailin" <luv2bsailin@...> wrote:
>
> Good stuff there Eric. It will take me a while to digest it all, but it looks reasonable. I think you may be a little pessimistic in assuming 250 cycles to 60% for the T-105s, but I don't have any hard data to back up that assertion. At any rate, the general sense sense I'm getting is that for lower power applications lead-acid compares favorably cost-wise, but there is a weight penalty. As you get above a few HP the balance tips in favor of LiFePo. Looks like they are pretty close in the 2KW range where I tend to operate much of the time, and the lower up-front cost is a definite advantage for me. Thanks for the insight.
> Jim
>
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