instead of buying a 50 dollar battery buy a 7 dollar one, works just as well for way cheaper
ive been useing this battery in my 7c and 10c for over a year, lasts quite a while, id guess around 10 hours maybe more.
http://www.all-battery.com/96v2000ma...pack11417.aspx
while your at it stock up on 6v reciever batteries http://www.all-battery.com/60vrcairbatteries.aspx