I've been noting rather low battery voltage on my DX8 transmitter LCD display for awhile. After pulling the battery out of the transmitter, its voltage was generally around 5.1 Volts DC.
Last Friday, after three flights of 6 minutes each, the DX8 low battery alarm went off. Again, the battery was pulled and measured 5.1 Volts DC.
Just could not figure out why Spektrum would have a battery voltage indication that was off by 0.9 Volts DC.
So, that battery was pulled from the transmitter, and checked on my Western Mountain Battery analyzer, at 300 Ma. The attached battery discharge curve shows the DX8 Battery voltage was correct, and that the battery voltage under light load is pretty much kaput.
So, its connector was cut off, and four Sanyo Eneloop "AA" Nih cells were wired up. And, the DX8 transmitter shows good voltage on the battery.
You'd think a $400 transmitter would have a battery that would last more than a year and a half. But, quality Eneloop batteries are cheap enough.