Sleep to low battery??s

Open lid and screen won't activate, nothing happens. Attach AC power and still won't activate. Think I heard some disk activity but not sure.
Norm wrote on :

Is this normal:

PB Ti is in sleep mode with lid closed and on battery power.

Open lid and screen won't activate, nothing happens. Attach AC power and still won't activate. Think I heard some disk activity but not sure.

Force restart was only thing that seemed to work. When up and running battery shows 4% remaining.

Is this normal behavior when PB is in sleep mode and runs out of battery?

BTW, PB G4 Ti running OS 10.2.3

Thanks.