Bob, I believe at 50 or 55 MPH constant level road you see about 12kW draw. Since the pack is almost 400V, this means about 30A. EVs typically are driving for about 1-2% of the time, for the rest they are charging or resting. But this is irrelevant - there is no relation between driving current and balancing, as long as you are not trying to *change* the balance while driving (Lee has a balancer that will prop up a weak battery while driving, this is certainly not the intention of the Leaf BMS).
The Leaf BMS is only trying to slowly adjust differences between cells in the pack due to imbalance in self-discharge. Good cells have almost no self-discharge. I have a pack of LiFePO4 that were used and some cells were abused. Few of them died, the survivors have a ratio 1:2 in self-discharge rate. It is very small still, only a few mA I estimate that some of the cells are 2mA, others up to 4mA. So the 10mA of the Leaf BMS would only need to balance during 20% of the time to remove the 2mA difference using its 10mA shunts. Since the Leaf BMS is always on, it can balance 24/7/365 so a small balance current adds up and as long as the *difference* in self-discharge between cells is always less than 10mA, it should be able to keep the pack in check. If not, then it is time to get a new pack. From what I have seen, the cells age quite equal in the same pack. Hope this clarifies. 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 http://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: Robert Bruninga [mailto:bruni...@usna.edu] Sent: Wednesday, October 05, 2016 12:25 PM To: Cor van de Water; Electric Vehicle Discussion List Subject: RE: [EVDL] How to Prolong Lithium-based Batteries - Battery University Wow! > the Leaf BMS will still be balancing the cells[all the time], > [because] it has only 10mA balancing capacity... What then is the nomimal discharge current on level ground at 50 MPH? My SWAG guess might be 10 amps? That means only about 0.1% balancing capability? Maybe Im missing something... Bob -----Original Message----- From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Cor van de Water via EV Sent: Wednesday, October 05, 2016 2:55 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] How to Prolong Lithium-based Batteries - Battery University Mark, The Leaf charges to approx 4.12V as "100%" (LeafSpy shows this around actual 90% real SoC - not always consistent, I have seen 89% and over 91%) and to approx 4.05V as "80%" (again, sometimes closer to 4.04 and sometimes closer to 4.06V) The lowest that I have ever seen my Leaf SoC was just above 15% real SoC on LeafSpy with the cells around 3.7V, the Leaf itself indicates this as empty, so I believe that the top and bottom 10+% are not used by the Leaf to avoid the extremes where the internal resistance of the cells rises and heat develops faster, leading to faster degradation. NOTE that even when discharged to 50%, the Leaf BMS will still be balancing the cells, it is always on as it has only 10mA balancing capacity so it is balancing all the time as long as the 12V battery is connected. I have even seen it occasionally balancing a cell with SoC below 20% but it will be much more aggressive at high SoC. Hope this clarifies, 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 http://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:ev-boun...@lists.evdl.org] On Behalf Of Mark Hanson via EV Sent: Wednesday, October 05, 2016 11:13 AM To: Electric Vehicle Discussion List Cc: L. David Roper Subject: [EVDL] How to Prolong Lithium-based Batteries - Battery University Hi folks It looks like in NMC lithium charging to 4.2 vpc is 300-500 cycles or to 4.1 is 600-1000 cycles or 4.0 is 2400-4000 cycles. Certainly overcharging is bad but I've seen other studies on high mileage Leafs in England that were 100% charged that showed little degradation after 50k miles. Just trying to figure based on real data if charging to 80% which loses the balancing function or going to 100% on my Leaf on each cycle is best. I assume Nissan isn't overcharging their cells on each cycle. It looks from the Leaf spy that most cells are at 4.0 volts at 100% charge. Does anyone have EOC data on the Leaf? My son drives it daily 15 miles round trip and then plugs in at home to 100% Thanks mark http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_ batteries Sent from my iPhone _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at 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 Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at 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 Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
