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