My father used a Imogene system for awhile.  He had been using bottles and a rental unit came through the supply company that let him use it.  I bought extra power supplies off of ebay to power it off of AC to make more convenient to not run off of batteries I think charges were $20. Had a power supply by kitchen table, favorite tv chair, etc He had the over the shoulder bag to carry.  Almost bought a system for him off of Craigslist but he got into the rental unit which did not cost him anything.  I think there were two battery sizes.  Smaller (lighter) battery was fine since unit could be plugged more often.