That is what I understood from your description: you are talking about self-discharge (the *parallel* resistor) not the internal resistance (the *series* resistor). Since the self-discharge *does* change the SoC of the cell, this is a totally different mechanism than the one we were discussing. NiMH and LiIon are very different animals.
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Thursday, June 20, 2013 2:56 PM To: [email protected] Subject: Re: [EVDL] EV Digest, Vol 8, Issue 30 Cor Your example below is exactly what I have come across in failing NiMH modules. So as you point out this bad cell can lose energy during discharging at a greater rate then there rest of the pack in series. The same results happen when charging. Don Blazer In a message dated 6/19/2013 11:30:57 P.M. Pacific Daylight Time, [email protected] writes: One example to illustrate: Say we have Lithium cells (any chemistry, but say the cell is at 3.5V rest voltage). Due to construction or abuse, the internal resistance of the cell has increased to 10 mOhm and you try to pull 500A from the string of cells. The resistor drops 0.01 (Ohm) * 500A = 5V while the cell tries to deliver 3.5V so if you measure the terminals of the cell under this load, you will see the cell at 3.5 -5 = -1.5V. The ideal cell is delivering a power of 3.5V * 500A = 1750 Watts. The internal resistance is sucking up and producing heat to the tune of 5V * 500A = 2500 Watts. Total power delivered by the damaged cell is -750 Watts (it is consuming 750 Watts of power from the adjacent cell by dropping part of the adjacent cell delivered voltage across its internal resistance) Still, if the heat does no damage and does not affect efficiency of accepting charge, then the high-resistance cell will stay in balance, it will just be inefficient and possibly disastrous in its operation if the internal resitance causes dangerous heating to occur. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130620/4360 3eef/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)
