Ron Natalie writes:

I mention the batteries because I once was a passenger in a IFR
(but VMC) NORDO plane and the pilot's hand held batteries were
also moribund. I did manage to get clearance to land at Dulles
with only the receiver working.

Lithium batteries will hold their charge for a decade at least. They
are also very light, and they provide high current on demand. I use
them exclusively for everything when I have the option.

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