at least one rechargeable cell providing {HEAD ~ relatively efficient stored energy output} at {TAIL ~ both relatively high and relatively low output current levels} 
at least one rechargeable cell providing { HEAD ~ relatively efficient stored energy output } at { TAIL ~ both relatively high and relatively low output current levels }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL