For example, {HEAD ~ the predetermined level} may be set at {TAIL ~ 20%} of remaining battery power 
For example , { HEAD ~ the predetermined level } may be set at { TAIL ~ 20 % } of remaining battery power
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH