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