[Elecraft] ... and solar power

[Bob]

PowerFilm folding panels have a maximum power transfer point that occurs
somewhere around 15.4 volts.  If the load can't absorb the power produced
at that time, the panel voltage will increase -- you can expect to see
somewhere between 18 and 20.5 volts as the load current approaches zero.
 Powerfilm themselves warns that a battery should not be used without some
sort of charge regulator unless the system load is so high that the battery
never approaches a 100% charge condition (which would allow the solar panel
voltage to increase to the point where the battery was overcharged, or the
attached equipment damaged).

http://www.powerfilmsolar.com/education/calculations/

I would suggest that anyone with a PowerFIlm panel producing 14.9 open
circuit in full sun has a defective panel, and should contact PowerFilm
about a replacement -- they are an excellent company and stand behind their
products.  I returned my 60 watt panel when the output current
unexplainably dropped by about 25%.  They quickly replaced it with a new
panel.

73, Bob, WB4SON