At my club, we have 5 older generation, non-glass gliders. The rest
of our fleet, club and private, totals perhaps 12 glass ships - all
with electrical systems (and one with a transponder).


IMHO, in FAA speak, an aircraft having only battery power does not have
an electrical system.

FAR 91.215:

(3) Notwithstanding paragraph (b)(2) of this section, any aircraft which
was not originally certificated with an *engine-driven* electrical
system or which has not subsequently been certified with such a system
installed, balloon or glider may conduct operations in the airspace
within 30 nautical miles of an airport listed in appendix D, section 1
of this part provided such operations are conducted—.......

Tony V.