Keith;
I don¹t think that the limited effects of Perkert, nor the cycles you get
taking LIFEPO4 batteries to 80% DoD is theory at this point.
Concerning redundancy, There are two ideas I have had concerning this. One
is to have a extra cell around that is kept topped off, charged once a
month, to serve as a cold swap if needed. The other is to again have the
extra cell, but have it in-line already as part of the pack. Let¹s say you
have a 48v pack. Add an additional cell, bringing up the nominal voltage by
3.2 volts. The BMS would have to deal with an extra cell (16+1), and charger
and the like, but if a cell failed, you would just reconfigure the pack, and
off you go. An intelligent BMS could do this for you, warn you of the
failure, and ³Ask you² to remove the offending cell.
Chris
On 7/25/09 12:46 PM, "aweekdaysailor" <aweekdaysailor@
>
>
>
>
> There is a point he makes in his articles which could be easily overlooked.
> Because you can take a higher depth of draw (DOD) with lithium (and to a
> lesser degree due to Peukert effects in lead-acid), you can get by with a
> smaller bank than equivalent lead-acid without compromising cycles (in theory
> at least).
>
> Valence has a little widget which shows this graphically (their chemistry is a
> little different than others, but same rules apply)
>
> http://www.valence.
>
> I would also advocate splitting lithium into 2 or more banks vs large single
> cells. Peukert is a non-issue, so no penalty for switching them, and nothing
> quite like the sense of confidence knowing you have a fresh bank available if
> you experience a cell failure or just a long load. The pricing slightly favors
> larger cells, but at a bare fraction of the total. You've also got both
> redundancy and sparing in this config (being error prone, I'm big into
> redundancy..
>
> -Keith
>
> --- In electricboats@
> , Chris Witzgall <chris@...> wrote:
>> >
>> > I don¹t think Nigel lives on the breeding edge of technology. Sure, he uses
>> > the latest stuff on the market, but except for a few, very expensive niche
>> > products, LIFEPO4 batteries are not on the market yet, while TPPL are. You
>> > can order a 12v 8D sized Odyssey battery, try that with a LIFEPO4.
>> >
>> > Give it a year or two, and I would not be surprised that he is singing the
>> > praises.
>> >
>> > Chris
>> >
>> >
>> > On 7/24/09 12:27 PM, "Nick Evans" <qgold.77@..
>> >
>>> > >
>>> > >
>>> > >
>>> > >
>>> > > Maybe we shd tell him about the group - most of the experts in the field
>>> > > are here - [:D]
>>> > >
>>> > > - Nick
>>> > >
>>> > > There's many a dip 'twixt ship and slip
>>> > >
>>> > > --- In electricboats@
>>> <mailto:electricboa
>>> <mailto:electricboa
>>> > > , "JJ Johnson" <jjoftheusa@
>>> > > wrote:
>>>>> > >> >
>>>>> > >> > HI EVERYONE,
>>>>> > >> >
>>>>> > >> > I have been looking at alternative battery chemistry for several
years
>>> > > and could never justify the extra expense of LI-ion. Then yesterday I
>>> > > received the current issue of Pro Boat Builder. Nigel Calder has an
>>> > > article on page 52 about his choice of battery chemistry for his boat.
>>>>> > >> >
>>>>> > >> > Go to <http://www.proboat.
2009
>>> > > issue to read his article. You might have to register but it is free.
>>>>> > >> >
>>>>> > >> > You just might decide to use TPPL (thin plate pure lead) batteries
>>> > > instead of any LI-ION chemistry.
>>>>> > >> >
>>>>> > >> > While you are on the Professioal Boat Builder site check out the
past
>>> > > issues for other articles by N.C. He is going electric in a big way on
>>> > > his new boat, but writes for the common boater which includes most of
>>> > > us.
>>>>> > >> >
>>>>> > >> > Enjoy,
>>>>> > >> > JJ
>>>>> > >> >
>>> > >
>>> > > [Non-text portions of this message have been removed]
>>> > >
>>> > >
>>> > >
>>> > >
>>>> > >>
>> >
>> >
>> >
>> > [Non-text portions of this message have been removed]
>> >
>
>
>
>
>>
[Non-text portions of this message have been removed]
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