Agreed. I never take my 54 100Ah (Thunder Sky) cells past 80% DoD, but that's enough for 60 miles range when driving somewhat conservatively in my little Porsche 914, and I haven't had any issues. I do notice voltage sag starting to increase, but not enough to be of concern. I turned off Peukert compensation on my LinkPro, and my Ah out vs. Ah in always matches almost perfectly (in fact, it's more likely to overestimate Ah out). I have some BMS data of a recent drive that took me to 80% DoD; contact me off-list if you'd like to have a look at how the cells were doing. Temperature had much more of an effect than SoC. In terms of discharge rate, I used to have my Z1K set at 1000A battery/1000A motor and the batteries never complained, but I tuned it down to 500A battery limit to try to baby my cells a little more, perhaps coax a couple of extra years out of them. My right foot doesn't have enough discipline without an enforced limit.
Keep in mind that you typically won't be discharging much past 1C, on average, and that's what the cells are often rated for. Even when they spec lower (0.3C, 0.5C), if you look at the discharge curves on the datasheet you'll see 1C almost always still gives rated capacity (or at least very close to it). At 50 cells x 180Ah, I imagine you'd be treating them pretty gently, so I think you can simply go by the published Ah rating x 80%, with a 20% 'reserve' capacity for emergencies/slop. For reference, my 2400lb 914 uses 1.25-1.5Ah/mile at 173V nominal. If you switch to lithium I don't think you'll regret it. The chemistry's only disadvantage in my book is the "don't charge below freezing" limit. That, and up-front cost. I get around the temperature issue by having a seasonal car, but up here in New England I would definitely spring for a temperature management system if I had a year-round driver. Up front cost is more than offset by lifetime cost: I was originally looking at 16 Optimas which would have given me ~13000 miles (500 cycles * 25 miles), and instead I got 17kWh of LiFePO4 from which I hope to see >100,000 miles (2000 cycles * 60 miles) for only about 2x the price. Cheers! -Ben On May 15, 2013, at 9:29 PM, David Nelson wrote: > While I see slight variation in the Ah used for a given trip depending on > battery temperature with my TS-LFP100AHA cells in a 2p20s arrangement I > have not had any issues ignoring the Puekert effect with my pack. You > should only use 70-80% of your pack Ah any way which is enough of a buffer > to more than mask any effect, especially with the CALB CA series cells. > There is a YouTube video of someone pulling nearly 1000A from a 180Ah cell > (or was it a 100Ah cell?). The voltage drop was minimal. For all practical > purposes you can ignore it unless you plan on pushing the limits all the > time. > > Considering what you are replacing you will see a huge improvement in > range, especially if you only used 50% of your AGM 20hr Ah rating. > > > On Wed, May 15, 2013 at 4:15 AM, Pestka, Dennis J < > dennis.pes...@covidien.com> wrote: > >> I saved this old e-mail from Peter, because it really honed in on what the >> Peukert Effect does to the range of your EV. >> See Below. >> >> Hit it right on the money for my 65 Datsun and its 156V pack of 65Ah >> Odyssey AGM's. >> I'm thinking of replacing them with (50) CA180FI, 180ah CALB LiFePo4 Cells. >> >> Question I have is the Peukert Effect on these Lithium Cells. >> I've heard they're much better that Lead Acid, or AGM's, but does anyone >> know the approx. adjustment % >> >> Thanks; >> Dennis >> >> >> 950 lbs. of what kind of lead? AGMs don't like to go below 50% Floodies >> can tolerate 80% as can Gels. >> >> 12V, 8V, or 6V batts? How many? How many AH are they rated for (20 Hr >> value)? >> >> >> Here's a calculation method I've found that seems to match well to what I >> get for range (can't remember >> where I found it): >> >> (Total pack voltage X AH rating of each battery) = watt-hours (whr) stored >> >> whr stored X 0.57 (adjustment for Peukert effect) X 0.80 (useable DOD for >> floodies or Gels) = usable whr >> >> useable whr divided by watt-hours per mile used (conservative value = >> 300-350; not sure how >> aerodynamic the Nash is) = range in miles >> >> >> Peter Flipsen Jr >> >> >> >> Thanks; >> Dennis >> Elsberry, MO >> http://www.evalbum.com/1366 >> http://www.evalbum.com/3715<http://www.evalbum.com/1366> >> >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: < >> http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130515/db06612c/attachment.htm >>> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> For EV drag racing discussion, please use NEDRA ( >> http://groups.yahoo.com/group/NEDRA) >> >> > > > -- > David D. Nelson > http://evalbum.com/1328 > http://www.levforum.com > > Nokia Lumia 920 Windows Phone 8 > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130515/aa2415b1/attachment.htm> > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use 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 For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
