you can see how this works out at
http://www.green-trust.org/peukert/
Steve Spence
Renewable energy and self sufficiency
http://www.green-trust.org
http://arduinotronics.blogspot.com/
On 11/14/2010 12:00 AM, Tom wrote:
>
>
>
>
> 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
> <mailto:electricboats%40yahoogroups.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%40yahoogroups.com>
>> >> [mailto:electricboats@yahoogroups.com
> <mailto:electricboats%40yahoogroups.com>] *On Behalf Of *Eric
>> >> *Sent:* Saturday, November 13, 2010 10:17 AM
>> >> *To:* electricboats@yahoogroups.com
> <mailto:electricboats%40yahoogroups.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>
>> >> <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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