The Activox portable oxygen concentrator offers the longest lasting internal battery of any portable oxygen concentrator. The 4L model is a great option if you have higher oxygen requirements and don’t want to compromise on battery life, weight or ease of use. The display screen on the control panel keeps you informed with clearly worded text. For example, if you are low on battery power, the message “LOW BATTERY” is shown on the screen. If you are charging the battery, the message “Charging Internal” or “Charging External” is shown. The display screen makes it easy to figure out alarms and constantly know the status of your POC.