Just cutting and pasting the answer directly:
The display will read “Charging” when the batteries are drawing a charge. It should read “Mains” when it is no longer in charging mode.
Facing the pump starting from left to right, the buttons are: On/Off, Vacuum Control Knob and the Let down
You can run a Battery Check to get an idea if the batteries are in good condition by:
Charge the pump for 12 hours or until the display reads “Mains”
After charge, turn pump on
Go to service menu by pushing the “On” button again while turning the Vacuum Control Knob.
Keep turning the Vacuum control knob until you get “Hres” (hour reset) then press the “let down” button and reset it to 0
Let the pump run until the batteries are drained and the display reads “Battery Flat” - Keep in mind the pump is programmed to shut down after 30 minutes to save battery life - it will need to be restarted.
Once the batteries are completely drained (Battery flat) Plug in to a wall outlet. Go back to the “Hres” . There should be a time indication. that should tell you how long the batteries are good for ( around 60 minutes
If the battery indicator is significantly lower than 60 minutes, you will need new batteries, if not Power Supply is not charging batteries. In an extreme case the Main board may not be reading either correctly.