My wife and I both use Resmed AirMini CPAPs when travelling. I purchased two of these DC Converters to use in our RV for times when we are camping at sites that have no electrical hookups. We have solar panels and two 100Ah Lithium Ion batteries in the RV. These travel power adapters worked like a charm for plugging into the 12V outlets in the RV. They appear to be very efficient as we only drew down about 10% of our battery capacity overnight despite running both CPAPs all night. These will be very useful for using anywhere you have access to 12V outlets, but no access to AC power such as in an RV, car, or boat. Highly recommended.