okashira
10 kW
x-speed said:okashira said:The lower performance of the PF compared to the PD at high current could be explained by the addition of this fuse you refer to.
EDIT: well, tests show the PF outperforms at high amps, (10A) PD slighly outperforms at 3A and they are very similar at low current (0.2A)
WTFknows.
This whole "B grade A grade" BS really makes comparisons difficult
Generally Panasonic reserves their "NNP" terminology for NCA chemistry cells. Do you have a link to this document?
Yes very small variations may be usual production spread, measurement/charge uncertainties, age.... coffee cup reading.
So PF is most likely still the same NNP chemistry with small fuse improvements etc.
Documents about the Panasonic NNP / NCR NiCoAl evolution:
http://www.embedded-world.eu/fileadmin/user_upload/pdf/batterie2011/Sonnemann_Panasonic.pdf (many details)
http://www.yeint.fi/pr/pr/files/li_ion_akut.pdf
http://industrial.panasonic.com/www-data/pdf2/ACI4000/ACI4000CE17.pdf
Thus Nickel is the main key to these new high cap frontiers ("Solid Solution among LiNiO2 enables High Capacity"). LG Chem names the chemistry of similar types (LG MH1, LG HE2) as "Ni-rich".
And a so called HRL (heat resistance layer) - in Panasonic wording - was the main key to enable such high energy densities for safe commercial use. Al adds to thermal safety, and Co as before to durability.
After all the precise chemistries and layering details are rather complicated and advanced today.
The new early CID fuse tripping feature may be a chemical which produces lot of gas beyond 4.5v or so quickly raising the pressure which trips the CID early; not consuming significant extra space.
The new NCR18650BF seems to be the first cell which has now a improvement from the plain graphite anode by adding SiO - as announced in that 2011 document. A real improvement of the NCR B high cap cell.
okashira said:member fellow says he discharged his PF's to 0V, kept them there for a week, and they came back OK.
Surely NCA can't handle that?
Well, overdischarge below 2V mainly attacks the Graphite anode, not so much the (LiCo, LiMn, NMC, NCA..) cathode: When all Li is gone out of the graphite, the graphite contacting metal will be oxidized -> increase of Ri, spoiling of electrolyte, thus increase of future self-discharge, later deposition of the dissolved metal and formation of dendrites, increased danger of internal shurtcuts even if the cell can be recharge firstly, ... Possible improvements of stability here (Does the PD vs PF really not "survive" with similar rates?) may be independent of cathode questions. Cathode is more exposed to stress upon overcharge and high discharge currents.
Yet its generally not allowed officially to recharge LiIon's from below 2V. Valid BMS'es shall go into permanent failure state once a cell is below 2.0v, not allowing recharge. For some cells "pre-charge" at low currents is allowed from 2.0v .. 2.5v (with subsequent self-discharge test).
I have seen most of what you linked...
take aways:
PSS = Lithium Manganese Hybrid (old, Panasonic doesn't market anymore)
NNP = New Nickel Platform aka NCA
NCA goes to lower voltage on discharge then NCO
NCA is WAY better at high temperature in terms of calendar life then NCO
(We know that NCO is much better then NCM and Li - Fe Phosphate per Youtube presentation I posted a while back, thus NCA should be far superior then both.)
BTW, Fasttech sells the NCR18650BF, branded by Sanyo. I know dampfakkus tested them and they were inferior to the B. But I am guessing they were rejects.