a battery mounted in {TAIL ~ the case} and connected to {HEAD ~ the power input socket} so the external battery charger can charge the battery 
a battery mounted in { TAIL ~ the case } and connected to { HEAD ~ the power input socket } so the external battery charger can charge the battery
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH