I have Lithium cells (CALB 180Ah) sitting in my garage since 1.5 years and have measured their self-discharge and plotted it in an Excel spreadsheet. I can *see* their self-discharge. I can *see* effect from ambient temperature on the change in self-discharge rate over time I can *see* the differences of up to a factor 2 in amount of self-discharge between cells that were initially charged to exact same state of charge (charged in parallel, then left for many days connected together in parallel, then disconnected all cells from each other and with every cell unconnected to anything, take a measurement with a DVM once every few days for a couple months.) If you did this, you would be able to tell as well.
Besides - the resident Lithium expert on this forum (who has helped to setup a Lithium-Ion cell factory) tells us that there is self-discharge, so I am seriously wondering why you continue to argue that self-discharge does not exist??? As for failures without BMS: Yes, I have helped investigate a burned-down conversion that did not have BMS. It is likely that in that case, a manufacturing defect in the cell was the root cause because the fire started at a moment that the pack was not connected: not charging, not discharging, just sitting there. There is a small chance that it was something that fell *on* the pack but since nobody was present at the time that the fire started, that is unlikely. I discovered that there was an anomaly in the layout (folded layers of some of the pouch cells inside the prismatic case) that is the likely start of the problem - a workmanship problem. But also that was never proven just like the fire with the Dreamliner which was never pinpointed to a root cause. Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of Paul Dove via EV Sent: Thursday, June 18, 2015 8:23 PM To: Michael Ross; Electric Vehicle Discussion List Subject: Re: [EVDL] Bicycle battery I agree with that. Sent from my iPad > On Jun 18, 2015, at 10:12 PM, Michael Ross via EV <[email protected]> wrote: > > A question for Paul DOve, > > Whence came your evidence of self discharging in Li ion cells? > > I have the other impression entirely - that there is no mechanism by > which self discharge is even possible. > > If cells are mismatched in a pack there can be an accumulation of > drift relative to other cells in a pack (which can cause problems), > parallele cells will equilibrate among themselves (why you want them > to be closely > matched) BMS and other electrical/electronic equipment can produce a > parasitic load across a pack, but a charged cell sitting alone on a > shelf does not lose charge. It's capacity can decrease so that > subsequent performance is less good, but there is no self discharge. > > Mike > > On Thu, Jun 18, 2015 at 10:59 PM, Cor van de Water via EV > <[email protected] >> wrote: > >> Paul, >> >> I presume you never ride in a car, because Ford's Pinto was a bomb on >> wheels and unsafe at any speed. >> >> Your line of reasoning does not warrant a serious response and I have >> given many reasons why a BMS is a good thing - I like to discuss >> based on arguments and data, not on lore and incidents. >> >> BTW, last I heard the root cause of the dreamliner fires is still >> unknown, there is suspicion about the quality of the batteries, >> similar to what caused laptop batteries to catch fire due to >> impurities embedded in the cells and trigger thermal runaway. >> I have helped to investigate a fire in a converted EV with >> Lithium-Ion prismatic cells that I suspect (but it was never >> conclusively proven) was caused by manufacturing defects. >> There was no BMS on that pack and it was not being charged, still it >> caught fire just sitting. >> One thing that I found was that what appeared to be a hotspot also >> showed severely deformed (folded crooked as if they were rammed into >> the prismatic case) cell plates (the original pouches that are >> contained in a bundle inside the prismatic cell) in one of the cells. >> But you can't say "they used a BMS so that caused the fire". If you >> have a source that proves that it was in fact the BMS causing the >> fire then I would be interested in a link. >> Here is what I have: >> >> http://arstechnica.com/business/2013/02/investigation-reveals-cause-o >> f-battery-fire-on-boeing-787-dreamliner/ >> https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_problems >> >> http://www.ifsecglobal.com/dreamliner-lithium-battery-fire-cause-stil >> l-unknown/ >> >> Regards, >> >> Cor van de Water >> Chief Scientist >> Proxim Wireless >> >> office +1 408 383 7626 Skype: cor_van_de_water >> XoIP +31 87 784 1130 private: cvandewater.info >> www.proxim.com >> >> >> This email message (including any attachments) contains confidential >> and proprietary information of Proxim Wireless Corporation. If you >> received this message in error, please delete it and notify the >> sender. Any unauthorized use, disclosure, distribution, or copying >> of any part of this message is prohibited. >> >> >> -----Original Message----- >> From: EV [mailto:[email protected]] On Behalf Of Paul Dove >> via EV >> Sent: Thursday, June 18, 2015 6:31 PM >> To: EVDL Administrator; Electric Vehicle Discussion List >> Subject: Re: [EVDL] Bicycle battery >> >> Even Boeing burned up dream liners with a BMS. >> >> Got any other argument besides everyone is doing it? >> >> >> >> Sent from my iPad >> >>>> On Jun 18, 2015, at 2:02 PM, EVDL Administrator via EV < >>> [email protected]> wrote: >>> >>>> On 18 Jun 2015 at 11:43, Cor van de Water via EV wrote: >>>> >>>> That pack is very nicely top-balanced and I expect that many more >>>> BMSs that you are not even aware of in daily appliances such as >>>> power tools will all top-balance. >>> >>> One more time. There is a really good reason that the only place >>> you find aversion to BMSes is among EV hobbyists. >>> >>> Real world electronics manufacturers -- the ones who build millions >>> of laptops, mobile phones, power tools and yes, commercial EVs -- >>> know that you don't sell a product with a lithium battery unless it >>> has ample smarts to protect the battery, the user, and the manufacturer. >>> >>> Trust me, these guys have bean counters looking over their shoulders. >>> They wouldn't be using BMSes if they weren't necessary. BMSes >>> protect the battery from early failure, the user from hazard to life >>> and limb, and the manufacturer from the lawyers! >>> >>> 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) > > > -- > To invent, you need a good imagination and a pile of junk. > Thomas A. Edison > <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> > > A public-opinion poll is no substitute for thought. > *Warren Buffet* > > Michael E. Ross > (919) 585-6737 Land > (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google > Phone > (919) 631-1451 Cell > > [email protected] > <[email protected]> > -------------- next part -------------- An HTML attachment was > scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150618/d4 > c725e6/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) _______________________________________________ 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)
