FrSky Taranis X9D Main Battery Replacement

The stock (green) battery pack is: NiMH-LSD 2000mAh 7.2 volts (6x 1.2v cells). JST-plug. I have two actually, but neither seems to be charging properly any more (they only run the radio for a few minutes).

I had to take a break a few years ago, but I have been trying to occasionally cycle/exercise this battery. I bought this radio in 2014, so I guess 8 years is not too bad.

I finally tried a "forming charge" (in external charger) on one of the battery-packs and that seemed to revive it a bit ... helped it keep the radio running for an hour or so. Problem is, it shows about 60% left and then goes to low-battery in minutes. Seems undependable to me.

Since this is the only 2.4ghz RC transmitter I own, the helpful guys in the Taranis forums pointed me to a replacement. I got a Taranis 7.2v Eneloop NiMH-LSD 2000mAh battery-pack from Batteries America.

This blue-one plugs right-in and works fine. With a good battery-pack, the internal/on-board charger works properly again. It's apparently back to it's original long run-times (seems like 5-6 hours best I can tell).

Back in the day, I did "calibrate it" ... verify that what the Taranis measures is the same as my volt-meter. After a full charge, it reads up to 8.7 volts briefly, but settles around 8.4-volts (1.4v x6) after a few minutes (and still shows 5 bars). Docs say that 6.6v (1.1volts x6) is about as low as you would want to drain the battery to or use radio at. I have these set fairly conservatively ... 

The Low-Battery Warning is set to 7.1 volts (Aloft manual suggests 7.0 volts)

The "Battery Meter Range" is set to 6.7-8.4 (so each 1-of-5 "bars" represent around 0.35 volts). 

IIRC, that tends to give me a "Low Battery" warning at 1-bar remaining (but is still plenty of power and time to land aircraft with around 6.9-volts left in the battery-pack).