Re: [Electric Boats] Re: Battery Life and Types

Lots of off grid homesteads are installing them. Primarily for longevity.

Steve Spence
Renewable energy and self sufficiency
http://www.green-trust.org
http://arduinotronics.blogspot.com/

On 09/16/2010 04:43 PM, Kerry Thomas wrote:
>
>
> 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%40yahoogroups.com>
> [mailto:electricboats@yahoogroups.com
> <mailto:electricboats%40yahoogroups.com>]
> On Behalf Of Eric
> Sent: Friday, 17 September 2010 4:59 a.m.
> To: electricboats@yahoogroups.com <mailto:electricboats%40yahoogroups.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
> <mailto:electricboats%40yahoogroups.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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