Hi,
Does anyone have a more in-depth explanation why li ion cells perform
poorly in cold weather ? It's well known that your range goes down when
the battery is cold. Lots of writers talk about the phenomena and advise
you about it but fail to give any real explanations. I think this
conversation may have come up a long while ago but it's hard to search
for.
I did a bit of research. Some authors talk about "intercalation", which
happens below freezing. Intercalation is when the anode becomes plated
with lithium ions instead of the ions being absorbed into the anode.
Obviously, that permanently ruins the battery. So, this is irrelevant
regarding poor range in cold weather.
I did find one article that might be relevant, though.
https://cen.acs.org/articles/96/i10/Rechargeable-battery-weathers-extreme-cold-conditions.html
They claim the electrolyte becomes viscous, slowing down the ion
movement. That's about all they say. But, I'll add my thoughts.
If the electrolyte is viscous, then I suspect the voltage potential
drops. Since watts-hours (energy) is V * Ah, you have less energy
available, assuming that the Ah is constant. But, what about internal
resistance ? For the same driving behavior, you'll need higher amps at a
lower voltage. Resistance loss is I^2 * R, so that loss should go up
significantly. I'm getting into a trap here: why doesn't the increased
resistance loss heat up the battery ? The nominal resistance is
extremely low, so maybe even at an elevated state there isn't enough
heat to affect the electrolyte's viscosity. Don't know.
Here's another article that talks about electrolyte. They talk about
preventing decomposition of electrolyte.
https://spectrum.ieee.org/energywise/green-tech/fuel-cells/lithium-additives
Obviously, the other major factors are cabin heat and defrost.
Peri
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
ARCHIVE: http://www.evdl.org/archive/index.html
INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
