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 

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-----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


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