Bill, By looking at his graph it looked like they all failed but two. Cells 1$ 2. The shunt balances were on 5 through 8. Those four failed first based on his graph.
johns conclusion stated that he could see no advantage to balancing cells since the balanced ones stayed no closer in voltage than the unbalance. And although I don't believe he said it in the conclusion the data appeared to me to indicate the balanced ones were further apart after the rest periods. Sent from my iPad > On Jun 28, 2015, at 11:27 AM, Bill Dube via EV <[email protected]> wrote: > > Watched the test on the video. In the end, he states "Four of the cells were > toast." at the end of the test. These were the cells that were _not_ > protected by the BMS. This looks like the BMS did its job quite well and the > test showed what was expected. > > I guess you can interpret results in whatever way fits your theory, but when > the unprotected cells were "toast" then you really have to stretch your > interpretation beyond the limits of credibility. > > There were folks right here on this list that performed a _scientific_ test. > They cycled cells to find their capacity, charged the cells fully, then > placed them in storage. After extended time on the shelf, they tested the > state of charge by repeating the cycle once more to ambivalently determine > the state of charge and capacity once again. They found, scientifically, > there was indeed self discharge. > > The peer reviewed literature agrees with the scientific tests that Lee > Hart tried for himself. Also, the peer-reviewed literature also says that > self-discharge doubles with each 10 Celsius increase in temperature (which is > a classic Arrhenius relation, as everyone knows that has taken a chemistry > course at the college level.) We all know that the end cells have a > completely different thermal environment than the middle cells, when placed > in a multi-cell pack. The cell temperature varies, causing self-discharge to > vary in a documented non-linear fashion. The cells gradually get out of > balance when placed in service in a high-voltage pack, even if they were > manufactured equally and perfectly. > > Do you understand the difference between "anecdotal evidence" and > "scientific test"? When you say "I measured the voltage and it was close to > the same" that is anecdotal evidence. While Lee Hart's experiment of > carefully measuring state of charge by cycling the cell before and after > storage was a scientific test. > > I'm wondering, are you so certain of your "anecdotal evidence" that you > would be willing to pay for burned cars, garages, and perhaps homes of the > folks that choose to follow your advice? Be careful what you wish for. > > Bill D. > >> On 6/28/2015 6:25 AM, Paul Dove via EV wrote: >> There were no parasitic loads on any particular cells. They were powered by >> the whole string in Hardys test. >> >> Sent from my iPhone >> >>>>> On Jun 27, 2015, at 10:34 PM, EVDL Administrator via EV >>>>> <[email protected]> wrote: >>>> >>>> On 27 Jun 2015 at 15:29, Peter Gabrielsson via EV wrote: >>>> >>>> He proved that putting parasitic loads on some cells in a series string >>>> vill cause the string to go out of balance. >>> That's what you'd expect, no? >>> >>> I see this less-than-ideal behavior in my Ping batteries, which are fitted >>> with an integrated BMS. I just recently learned that although the current >>> BMS they use draws its power from the entire battery, the older ones >>> (including mine) drew BMS power from the lowest 4 cells. >>> >>> Thus my BMS will indeed tend to imbalance the battery, especially if it's >>> not cycled regularly. However, the BMS has a "charged" LED for each cell, >>> and the only time I see more than a few minutes from first LED to all 8 is >>> when I've let it sit for months between uses and charges, something I don't >>> really recommend. >>> >>> BTW, I just checked the capacity on these batteries. They're 4 years old >>> and seem to be holding up pretty well. They're rated for 10ah; one is >>> producing 9.7ah and the other 10.0ah. This is to a 19.8v cutoff (just >>> slightly less than 2.5vpc average). >>> >>> David Roden - Akron, Ohio, USA >>> EVDL Administrator >>> >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >>> EVDL Information: http://www.evdl.org/help/ >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >>> Note: mail sent to "evpost" and "etpost" addresses will not >>> reach me. To send a private message, please obtain my >>> email address from the webpage http://www.evdl.org/help/ . >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >>> >>> >>> _______________________________________________ >>> 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) > > _______________________________________________ > 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) > _______________________________________________ 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)
