At {TAIL ~ the primary power rate}, {HEAD ~ a battery} may have a life of, for example, two hours 
At
At { TAIL ~ the primary power rate } , { HEAD ~ a battery } may have a life of , for example , two hours
REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH