You can check the battery voltage by pressing down on the volume knob. The number on the top by the RSSI is the battery voltage. As far as charging, it is better to charge the batteries outside the scanner. The charge time depends on the battery type, the mAh ratting.and the charger mA. I am not sure what the uniden chargeing circuit is rated. If I would to gues I would say about 150 to 200 mA. To figure out the charge time try this: Rechargeable battery charging time and mA current calculator | Convert to units and culinary measures.I currently have a set of chateau rechargeable batterys in. Is there a way to check the battery life on the scanner and how long should I charge the scanner for?