[Kenwood] What effects from low battery in TM-255A?

[John O. Newell]

What would the effects of a low battery condition in a TM-255A?  The background is that my TM-255A powers up fine, but if left on (rx only, no tx), it won't power back up for many hours after it has been turned off.  I'm wondering if this could be caused by the lithium battery becoming weak, and then recovering?
Does the circuitry in this (or other) radios provide any charge to the Li cell under any conditions (e.g., power applied from the PS but rig powered off)?
Tks/73
John Newell KB1FPM