Does it retain a charge while parked without charging? i.e. - if I go out hunting early in the morning and come back after dark will it still have the charge when I left it?
I'm not a PT but I can't imagine yoga would make it worse. Maybe just focus on back specific poses. I have a dvd (yeah, I'm old) that's Yoga for back pain.
Try yoga. I sit a lot for work and once in a while my back starts bothering (which can also be hamstring tightness). I do yoga for a couple weeks and it always gets better.