Are you getting the reading of 100% from the monitor. Have you access to a multimeter so you can check voltage at the battery .
How good is the battery itself. Have you let it go low too often.
Maybe it won't hold a charge any more and quickly drains when under load.
How good is the battery itself. Have you let it go low too often.
Maybe it won't hold a charge any more and quickly drains when under load.