To check in on line and in the fine print of the ticket the battery issue is addressed.
In the regular battery section which is quite detailed there is a link to the Special Needs Section:
We do not require information concerning the extent of a disability, however, the more information we have about you, the better prepared we are to meet your needs. United requires 48 hours advance notice and an hour in addition to the published airport check-in processing time of your originating airport if you:
Need onboard medical oxygen in flight (available on flights between Guam (GUM) and Tokyo (NRT) and flights between Guam (GUM) and Honolulu (HNL))
Will be using your FAA-approved respirator, ventilator, continuous positive airway pressure (CPAP) machine or your own personal oxygen concentrator (POC) (United does not provide POCs)
Require disassembly and/or packaging of a wheelchair battery
Will be transporting an electric wheelchair on an aircraft with fewer than 60 seats
Are traveling with a group of ten (10) or more people with disabilities
Plan to travel with an emotional support or psychiatric service animal in cabin
Special meals require a minimum of 24 hours advance notice, however we appreciate as much advance notice as possible.
That sums it up. The man did not touch bases with the airline. When you don’t do your homework, you end up crawling.