Evan, we've been on this path for a long time :-) I decided to go for BMS and cell manufacturing while being an ev active. So I hate to see projects going up in flames. I know how it feels with NMC cells. :P
Shallow cycling helps but it really takes only one deep cycle to be in trouble. Say your charger breaks down at the remote end you drive back to home. LFP cells do burn too. Higher self ignition temperature has given a false feeling of safety. -jukka 22.4.2014 17.48 kirjoitti "Evan Tuer" <evan.t...@gmail.com>: > Hi Jukka, > Yes, don't get me wrong, I'm not arguing against having a BMS (if you > remember I was talking BMS strategy with you back in 2003? at a BVS > meeting in Southampton). I think I'm on borrowed time until I replace the > BMS, but circumstances have produced this "experiment". > > The car is used daily, discharging about 50-55% of the capacity. Sometimes > shorter trips, and rarely longer trips using 80% or more. > > I will eventually try to balance it manually and see what sort of > difference there is, or maybe the pack will die first. I don't think it > can be too bad or I would already have reversed some cells on longer trips > and noticed that in the total voltage. > > Regards > Evan > > > On Tue, Apr 22, 2014 at 3:28 PM, Jukka Järvinen <jarv...@gmail.com> wrote: > > > Evan, can you open a bit that 50.000 mile cycles? How shallow or deep > > cycles you take? > > > > "Overcharge" balancing was showcased in China already in 2006 or so. It > > works but kills cells. Check what yout voltages are at EOC. This would > help > > us to understand your special conditions and success. > > > > Also there are chemical additived to activate shuffling when voltage > > threshold is met. This could be something CALB is using. It can add self > > discharging. > > > > Or maybe you have been able to get good pack and BMS did good job on the > > 1st years. > > > > Is it an agreement cells do not eventually die? Or when they do it's > always > > happening with noticeable increments without any chance for accident? > > > > When BMS fails it should render further damage impossible/unlikely to > > occur. Many designs are drawing energy from cells even when off. That is > > bad idea. There is alot of shit for BMS. > > > > If you look at the statistics how many trips are done in car without > > collision and then in how many collisions there was any difference if > seat > > belts were on or not. Can you still argue seat belts are not smart to > have? > > > > BMS is there to deal with many variables and with accurate measures. It's > > the seat belt. > > > > -Jukka > > > > 22.4.2014 12.44 kirjoitti "Evan Tuer" <evan.t...@gmail.com>: > > > > > My experience differs. I have CALB 180AH blue cells in my car, which > has > > > covered more than 50,000 miles in about 4 years. I haven't looked at > the > > > pack once since installing it. I had a self-built BMS monitoring the > > pack > > > to start with, but it got water damaged and I never got around to > fixing > > > it, so for the last 2 years the pack has looked after itself > (effectively > > > it's been "top balanced"). > > > > > > > > > On Mon, Apr 21, 2014 at 12:05 AM, Cruisin <crui...@live.com> wrote: > > > > > > > After selling CALB cells for over 5 years and using them in my own > > > > conversion, I can tell you from experience the following. At least > 15% > > of > > > > the cells will change so much in the first year the BMS will react to > > > your > > > > disadvantage of early charging termination and early over > discharging. > > A > > > > one > > > > year warranty that is promised is hocus. the second year will > > experience > > > a > > > > 10% failure with no warning of a cell. This makes your car unusable. > > > > Further > > > > experience with other Chinese cells is no better, or worse. I now > sell > > > and > > > > use the Nissan Leaf module that is half the price and so far no > > failures > > > > like the CALB. I would not ever recommend a CALB cell to any > customer. > > > > Those > > > > that are pushing the cells like EVTV have inventory they want to > unload > > > > before their is no more demand for Chinese cells. My customers who > have > > > > converted to the Volt and Leaf cells, made by the same S Korean > > > > manufacturer, are really happier with the results. No more stagnant > at > > > rest > > > > loses that you have experienced. Look at what cells are used in the > > > popular > > > > plugin cars that are required to provide a 8 year warranty in > > California, > > > > no > > > > Phosphate. CALB would be out of business if required to provide a 8 > > year > > > > warranty. They don't even recognize their one year warranty. You > wonder > > > why > > > > you are having problems, wake up and smell the coffee. > > > > > > > > > > > > > > > > -- > > > > View this message in context: > > > > > > > > > > http://electric-vehicle-discussion-list.413529.n4.nabble.com/self-discharge-of-CALB-180Ah-LiFePO4-cells-tp4669067p4669069.html > > > > Sent from the Electric Vehicle Discussion List mailing list archive > at > > > > Nabble.com. > > > > _______________________________________________ > > > > 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) > > > > > > > > > > > -------------- next part -------------- > > > An HTML attachment was scrubbed... > > > URL: < > > > > > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140422/72edaa01/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) > > > > > > > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140422/717f4241/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) > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140422/bcb7f3a2/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) > > -------------- next part -------------- An HTML attachment was scrubbed... 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