I never paid attention to the voltage vs temperature thing, but my
engineering training says that you are correct, Dr. Guy.Â* As to the full
voltage thing with the Li batteries, yes, they hold full voltage...Â*
Until they don't, and then they simply turn off, they don't run at
reduced power output as the SLAs do.

With the SLA batteries, I always used two batteries on a typical flight
in the Rockies, usually switching at around 3 hours.Â* With the LiFePO4,
I would easily run 5 hours and never have to switch, though, since I had
a separate tail battery, I kept a fully charged battery there.Â* And, as
I've said before on this group, after watching the batteries carefully
while charging on the concrete floor of my garage, I took the big step
after a year of leaving them installed in the glider with the proper
charger attached and plugged in.Â* Never a problem.Â* Your results may vary.

On 5/17/2018 6:29 AM, wrote:
I want to concur with Dan.
I fly out of Minden and we cruise between 15,000 and 17,999. It is COLD at that altitude.
My lead batteries would lose voltage as the temp dropped. After three hours at altitude they were lucky to put out 11 volts. Of course, when the batteries warmed up alter landing they had full voltage.
The LiFePO4 batteries do not seem to affected by cold soak. They work the whole flight at full voltage.

--
Dan, 5J