Here is a cheaper solution to the problem of a dead laptop battery:
Get a power converter that you plug into your car's 12V power outlet.
That, and a short extension cord: Drive up to your glider, hook it
all up, and never worry about a dead laptop battery. You always have
your tow vehicle with you anyway, so why not use it's battery?

My setup? A free Toshiba Satellite 2545XCDT (I just asked around and
a friend handed it to me - dead battery, too slow, no longer useful at
his place of business) running Win98, and $40 for the power converter
at CompUSA. Runs SeeYou just fine (3D is a bit slow), talks to my
SN10 and GR1000 logger in a DOS window, has a real serial port, and if
it breaks I just use my other laptop until I can find another cheap
replacement.

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