The PowerBlock 500 (DRPB500C) has a power saving feature where if the load is less than 5 Watts for an hour, then the device will shut off. The purpose is to prevent the scenario where the unit is accidentally left on (while in storage or something like that) and then it slowly drains out the battery. The reason it is set at 5 Watts is because this is the smallest power increment that the processor is able to detect (i.e. can't be 4W or 2W). This is a very common power saving feature and virtually all products have this type of feature. So, it is intentional, but we recognize that it could cause an issue in certain use case scenarios.
To prevent the unit from shutting off, you could just add another low consumption device that would add to the CPAP to exceed the 5W minimum. Here's a few suggestions (wattage shown is minimum W):
- Clock Radio (turn the radio on but volume down/off ~1-3W)
- Home Phone (~3W)
- Echo or Alexa (~2-5W)
- Wifi/Internet Router (~4-5W)
- LED Christmas Lights (~5W)
- LED Light Build (~5-7W)
- Small Table Fan (~10W)
- Inkjet Printer (~10W)
- Air Purifier (~25W)
- DVD Player (~26W)
- Humidifier (~35W)
- Small Water Feature (~35W)
Some other potential options (with one caveat, when the device's internal battery is fully charged then it won't likely draw enough power again and it may shut off).
- Phone or Tablet (preferably using an AC adapter 4W-10W )
- Electric Toothbrush Charger (6W)
- Nintendo Switch (7W)
- Portable Phone Charger (4-7W)