Tony Verhulst wrote:
wrote:
Nice presentation snipped
... One of the curves shows the
rapid voltage drop of a cell freezing as it discharges (some thing to
worry about on that next really long and cold wave flight :-)

If we had properly designed heater elements surrounding the battery,
powered by the battery itself, could we expect more "useful capacity"
from the battery on those cold flights? Useful capacity being defined as
the amount of current delivered to the avionics.

Yes, if the battery is well insulated so the heating doesn't require
much current, and if it is relatively warm before you launch (usually
the case), so current isn't required to warm it initially. Installing a
warm battery just before flying is one way, or an obsessed pilot could
connect external power to the heater to warm the battery (to, for
example, 90 deg F) before the flight, so no power is required for
heating during the flight.


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org