Thanks for the info Jay. I have been looking but no luck yet with any used car part dealers locally. The area I live in (Nova Scotia) doesn't have a lot of EVs on the roads so not much to be expected at the wreckers. Getting used cells from afar would be costly if not impossible to ship, think it would be cheaper & easier to ship loose hand grenades lol.
On Fri, Mar 15, 2019 at 11:39 AM Jay Summet via EV <[email protected]> wrote: > You can certainly get used Leaf packs in the $2500-$4000 range from auto > dismantlers / wrecking yards. They have 48 8v modules in the 40-60 AH > range depending upon age, so you can use them in 8 parallel 6 series to > get a 48volt (50.4 volt max) pack with 320+ AH of capacity. > > Plus you don't need to bother with liquid cooling connections...(which > may be a plus or minus depending upon how hard you are hitting them...) > > Jay > > On 3/15/19 9:20 AM, Dan Baker via EV wrote: > > Wow lots of great info. So I guess the counteraction of temp rise & > > voltage compensates for any losses from Peukert's equation in Lithium > under > > normal operating conditions. I suspect the equation is still applicable > to > > Lithium but at much higher draws, far past the C rating i.e. the battery > > will eventually lose more energy to heating than it can compensate with > > voltage rise. Of course that heat will destroy the battery so staying > > inside the C rating will avoid damage and Peukert effect? As suggested I > > have decided to do as close to real world loads and will do as close to > the > > amperage my boat typically draws, 100amps @ 48v. Where as I may be > testing > > with a smaller set of battery (don't want to order the whole lot and get > > 100% ripped off if they are garbage) I may reduce the load to what it > would > > see with a full pack and not exceed the stated C rating (if I go with 2 x > > 48v 100ah packs, each pack would only see a 50 amp draw) > > > > The concern on Alibaba battery quality had me double think this yesterday > > and I dug through the web trying to find a reasonably priced alternative. > > There is an aftermarket GM parts company called GMpartsdepot Canada, they > > sell a refurbished 2013 volt pack online for 2400 dollars CAD. It didn't > > say anything about a core return so I inquired to confirm. Apparently > it > > didn't matter, they won't sell it to me without going through a dealer, > > bummer. > > > > On Fri, Mar 15, 2019 at 9:56 AM paul dove via EV <[email protected]> > wrote: > > > >> Peukert's law was developed for Lead-Acid batteries, and works well in > >> that application. > >> > >> It does not necessarily apply to other battery chemistries, especially > >> Lithium-Ion batteries. Lithium-Ion batteries tend to self-heat during > rapid > >> discharge, and the Nernst Equation predicts battery voltage will > increase > >> with temperature. Thus, the effect of increased resistance is offset by > the > >> self-heating effect. This advantage of Lithium-Ion batteries is a > >> well-known advertised feature. In a research paper, a 50Ah lithium-ion > >> battery tested was found to give about the same capacity at 5A and 50A; > >> this was attributed to possible Peukert loss in capacity being > countered by > >> the increase in capacity due to the 30◦C temperature rise due to > >> self-heating, with the conclusion that the Peukert equation is not > >> applicable. > >> > >> > >> > https://www.google.com/amp/s/www.researchgate.net/publication/245106038_A_critical_review_of_using_the_Peukert_equation_for_determining_the_remaining_capacity_of_lead-acid_and_lithium-ion_batteries/amp > >> > >> Sent from my iPhone > >> > >>> On Mar 14, 2019, at 10:19 PM, Lee Hart via EV <[email protected]> > wrote: > >>> > >>> Michael Ross via EV wrote: > >>>> I am not sure about previous discussions and you may know this: > >> Peukert's > >>>> Law is not applicable to Li ion cells in any way. It only relates to > >> lead > >>>> acid cells. > >>> > >>> I agree with the rest of what you said, but not with this. Peukert's > law > >> says nothing about the chemistry involved; it applies to *all* types of > >> batteries and all chemistries. > >>> > >>> Peukert's equation applies to any battery or cell that has internal > >> resistance, and that has a minimum "cutoff" voltage below which it is > >> harmed. It simply states that the higher the load current, the lower the > >> apparent amphour capacity. High currents cause a larger voltage drop, so > >> you reach the "cutoff" voltage before the cell is truly dead. > >>> > >>> The amphours are not "missing"; you just can't get them without > reducing > >> the load current, or pulling its voltage below the safe minimum. If > you're > >> willing to shorten the life of the cell, you can still get it. > >>> > >>> Peukert matters more for lead-acids because they typically have a > higher > >> internal resistance. In particular, lead-acid internal resistance goes > up a > >> lot as the cell approaches dead. Most other chemistries do not have this > >> large change in internal resistance as a function of state of charge. > >>> > >>> -- > >>> Any intelligent fool can make things bigger, more complex, and more > >>> violent. It takes a touch of genius, and a lot of courage, to move > >>> in the opposite direction. -- Albert Einstein > >>> -- > >>> Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com > >>> _______________________________________________ > >>> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > >>> http://lists.evdl.org/listinfo.cgi/ev-evdl.org > >>> Please discuss EV drag racing at NEDRA ( > >> http://groups.yahoo.com/group/NEDRA) > >>> > >> -------------- next part -------------- > >> An HTML attachment was scrubbed... > >> URL: < > >> > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20190315/23251fe5/attachment.html > >>> > >> _______________________________________________ > >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org > >> Please discuss EV drag racing at NEDRA ( > >> http://groups.yahoo.com/group/NEDRA) > >> > >> > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20190315/10d66668/attachment.html > > > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Please discuss EV drag racing at NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -------------- next part -------------- An HTML attachment was scrubbed... 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