When you connect external power to the scanner, such as from your ac adapter, the scanner will always ask if you want to charge the batteries, If you left the ac adapter connected, and turned the scanner on & off through the power button, you would not keep getting that message.
If you are seeing "150mAh" and a one hour charge time, that is the wrong setting.
Press the Menu key
then select Advanced Menu
On the Advanced Menu screen, select "Set Charge Time".
On the Set Charge time screen, you enter the size of your rechargeable battery. One of the more common sizes is 2000mAh, but there are other sizes smaller and larger than 2000mAh.. Enter whatever size battery you are using (all four should be the same size & preferably brand) and press Accept. That will set the charge time for the batteries you are using.
You are better off to charge the batteries in an external 'smart' charger. The charge circuit in the scanner is based solely on time, and does not take into account how much charge (if any) the batteries need. If you leave your AC adapter connected to the scanner, you should be able to say "No" when you get the "Charge Batteries?" prompt & it normally will not keep asking every time you turn the scanner on. But if you are unplugging it each time, then when you reconnect power, it'll ask again.