RE: I have a full 110 V battery charger (on full power) to the battery
(during start efforts) so I
assume that the battery is giving full charge.

 Bad assumption unless you have a really beefy charger.  Sitting since
October if the battery is more than a couple of years old is most likley the
problem.  Starting it a couple of times during that period but not running
for any period of time just pulled the battery down more, the draw to start
probably was not replaced by an ideling engine for just a few minutes.  Let
the battery charge or use a jumper battery to get it going.  This winter my
six year old starting battery started crapping out if left to sit for more
than a couple of weeks, new battery in place now.