ORIGINAL: rmh
do a voltage depression check on the cells - - I use a Horizon meter which allows .5 or 1 or 2 amps load
On 2 amps a NEW Eneloop 2000ma pack (which some guys are buying as rx packs), shows 5.5 volts freshly charged BUT with only a 2 amp load - it sinks to 3.9 volts- which means it has very minimal ability to deal wit h even small micro servos which are the popular digitals of 40 in ounch torque - these draw 300ma each just in casual use
I am certain the vast majority of unexplained "failures ar e simply voltage depression.
+1 I lost a few planes this way when Ifirst migrated to 2.4 gear. Spectrum got the message and redid their software to dramatically shorten the reconnect time when a low voltage shutdown happens. The really simple backup when using the smaller packs is to plug a capacitor into the receiver - It handles the short load spikes and weighs only a few grams. I use them on all of my small pack planes.
HS-81s don't draw very high, but the HS-65s are pigs, and I typically get 3 or 4 flights from a 350mah pack with HS-81s.
EG