The field of the invention generally relates to {HEAD ~ cell phone battery systems} that ensure {TAIL ~ a user} has reserve cell phone battery power for emergency calls 
The field of the invention generally relates to { HEAD ~ cell phone battery systems } that ensure { TAIL ~ a user } has reserve cell phone battery power for emergency calls
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH