I see on the beutilityfree site that the cell Ah specs are given at the 100hr rate. That got me thinking about Peukert effect losses with this chemistry. Anybody know how these cells perform at high discharge rates, say C/5 and C/2?
-Tom
--- In electricboats@yahoogroups.com, Steve Spence <steve@...> wrote:
>
> As a off grid solar installer, I agree with you.
>
> NiFe batteries are available at
>
> http://www.zappworks.com/
>
> and
>
> http://beutilityfree.com/
>
> Steve Spence
> Renewable energy and self sufficiency
> http://www.green-trust.org
> http://arduinotronics.blogspot.com/
>
>
>
> On 11/13/2010 03:25 PM, Kevin Pemberton wrote:
> >
> >
> > One cell that seems to get neglected on this list is Nickel-Iron. I
> > believe they are likely the best of all batteries even though they are
> > an old tech. Some battery banks still in use are over 50 years old.
> > They don't care much how they are charged or discharged. They don't
> > care if they are left to discharge and over charge or complete discharge
> > fails to bother their life. Most of the time when they don't supply as
> > rated a simple replacement of the electrolyte will put them back in
> > original condition.
> >
> > It is true that they self discharge but this looks to me to be of little
> > importance and this is why:
> > A lead acid battery must be kept maintained with a trickle charge. This
> > process plates the plates with the antimony that strengthens the
> > plates. Nickel Iron can be left unattended and charged before you need
> > to use your boat. Constant current charger is all that is needed to
> > charge the nickel-iron battery because it can be overcharged without
> > worry. This leads to lower charger expenditures. Nickel Iron is not
> > cheep! But what is? Subtract High dollar equalizers and 3 stage
> > chargers and the price seems more manageable. Take the maintenance
> > chargers out of the picture and thinks may even look better. The fact
> > that alkaline solution is used as an electrolyte and factor that the
> > batteries will not be replaced in your lifetime and maybe your
> > children's, and the two times you do need to be replaced and nickel iron
> > looks very good. I bring this up because some are now looking at
> > lithium batteries as an option. The thought scares me because they are
> > so easily destroyed, and the price is out of this world. Edison
> > developed the battery with an eye to electric vehicles, what are we
> > thinking?
> >
> > Kevin Pemberton
> >
> > On 11/13/2010 11:47 AM, Myles Twete wrote:
> >
> >>
> >>
> >> Thanks Eric. That should inform folks who don't understand the
> >> tradeoffs. My point is just that having more than a 500-1000 cycle
> >> battery charge life is great advertising, but is pretty useless for a
> >> seldom used boat. And given this infrequent usage, I personally
> >> cannot justify even buying new flooded PbA batteries, let alone AGM,
> >> let alone Lithium of any chemistry. My 6 used T105's cost me $120
> >> total…even though the really only deliver less than 100ah at this
> >> point, I expect they will last another 3 years at least and for me,
> >> this scenario cannot be beat.
> >>
> >> Indeed everyone will weigh the tradeoffs differently…and should I
> >> personally get into a more financially stable situation, I might be
> >> tempted to add a string of Lithium to the boat.
> >>
> >>
> >>
> >> It's really great seeing so much more activity on this list these days
> >> with very very constructive and informative dialog. It truly helps to
> >> share your experiences out there so that new folks coming here realize
> >> that they're not crazy after all in wanting to go electric.
> >>
> >> Thank you all!
> >>
> >>
> >>
> >> -Myles Twete, Moderator, Electric Boats
> >>
> >>
> >>
> >> *From:* electricboats@yahoogroups.com
> >> [mailto:electricboats@yahoogroups.com] *On Behalf Of *Eric
> >> *Sent:* Saturday, November 13, 2010 10:17 AM
> >> *To:* electricboats@yahoogroups.com
> >> *Subject:* Re: [Electric Boats] Picking batteries
> >>
> >>
> >>
> >>
> >>
> >> Myles,
> >>
> >> You make a good point. Once cycle life gets to be about 500 cycles,
> >> the chances of having the batteries expire from cycle age are pretty
> >> low for pleasure boaters like most of the people here. That said, I
> >> know that for many boaters (me included) FLA batteries often die with
> >> low cycle counts from mis-management. With their higher self-discharge
> >> rates, FLA batteries will sulfate if not kept on a consistant charging
> >> routine.
> >>
> >> AGM batteries seem to survive inattention for longer periods without
> >> significant degradation.
> >>
> >> Lithium batteries, LiFePO4 batteries specifically, have a much longer
> >> shelf life, and should be able to survive 6 months of sitting without
> >> any noticible loss of capacity.
> >>
> >> Of course, with the considerable investment for any battery bank,
> >> having an automated charging system, either plugged in or renewable,
> >> will help any battery live closer to its potential.
> >>
> >> So my takeaway from this is that cycle life is not as critical for
> >> most of our applications. Attributes like size, form, energy density,
> >> the ability to deliver more of the stored energy, and cost could be
> >> more important factors in choosing your battery bank.
> >>
> >> ======================================
> >>
> >> Even though FLA are obviously cheaper than our other major battery
> >> types, I believe that they are least efficient for their size and
> >> weight. I find AGM to be a good compromise between cost and delivered
> >> energy. And finally, Lithium are half the volume and weight as either
> >> lead acid type and usually deliver more Wh per charge for the same Ah
> >> ratings, for a consdierably higher cost.
> >>
> >> I have found that a rough rule of thumb is that AGM cost about twice
> >> as much as FLA for the same size, weight, and Ah rating. They will
> >> deliver more range in our typical use cases. Lithium batteries cost
> >> about 50% more than AGM for batteries that will deliver the same
> >> range, but are rated 20% lower in Ah, and are 60% smaller and lighter
> >> than AGM or FLA. This rough estimate includes BMS modules that will
> >> prevent any high or low voltage event and help keep the individual
> >> cells balanced with each other.
> >>
> >> Everyone here gets to decide what is most important to them. I picked
> >> LiFePO4 batteries for many of the reasons listed above, but mostly
> >> size and weight. Cycle life was not a consideration.
> >>
> >> Fair winds,
> >> Eric
> >> Marina del Rey, CA
> >>
> >> --- In electricboats@yahoogroups.com
> >> <mailto:electricboats%40yahoogroups.com>, "Myles Twete" <matwete@>
> >> wrote:
> >> >
> >> > Interesting note on cycle life.
> >> >
> >> > It would take me 150years to go thru 6000 charge/discharge cycles
> >> with my
> >> > boat.
> >> >
> >> > Even if you were to use your boat every single day, it'd take over
> >> 15yrs to
> >> > reach that cycle count.
> >> >
> >> > Not even the manufacturers of these batteries advertise them to last
> >> 15yrs,
> >> > let alone 150yrs.
> >> >
> >> > Cycle life is meaningless to me and my boat except that if I were using
> >> > Lithium cells, one overcharge or one over-discharge and the cycle
> >> life goes
> >> > from awesome to pitiful.
> >> >
> >> > -Myles
> >> >
> >>
> >
> > --
> > Ubuntu10.04, Acer AspireOne, Virgin Mobile 3G Broadband2go.
> > Doesn't get any better than this!
> >
> >
>
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