Interesting to read about NiFe cells.
The only place I have seen them used is in fire lanterns on old ships.
They still work and hold a good charge at 30 years old.
-----Original Message-----
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
On Behalf Of Eric
Sent: Friday, 17 September 2010 4:59 a.m.
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Battery Life and Types
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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