In Electronics Posted by Mark Spencer Feb. 22, 2014
New Taranis RC transmitter from FrSky is maybe todays best bang for the buck, but why on earth did they design it for obsolete NiMh battery packs. Taranis battery that comes with transmitter is only 800mAh and since it's NiMh with high self-discharge rate. This means you have to charge it every time you are planning to go to the field.
With FrSky Taranis transmitter becoming popular there are several solutions to this problem. One is to replace Taranis battery with bigger NiMh battery pack, which means you can still use Taranis internal NiMh trickle charger. While this somewhat solves fully charger Taranis battery field lifetime, you still have to charge it for hours before every field visits since NiMh batteries will discharge just by sitting on the shelve.
Good thing is Taranis can work with higher voltages such as 11.1V supplied by 3S LiPo batteries, but LiPo battery does not like being constantly on full charge, which might damage the batteries. Another thing is if you accidentally leave your transmitter turned on and discharge LiPo beyond limit, it might result in fire.
Best option so far for Taranis battery would be LiFe, which is much more stable then LiPo. The only problem is not much LiFe batteries on the market today can fit the battery bay of the Taranis, plus you have to remove the battery cover to charge it each time since internal Taranis battery charger supports only NiMh. On HobbyKing the only LiFe battery that can fit Taranis battery bay is this one, HobbyKing 1500mAH LiFe 3S 9.9v Transmitter pack. However it's reported by several users that this LiFe pack will puff and once it does, it might not fit the Taranis battery bay anymore.
Another clever solution is custom 3d printed Taranis battery bay cover.
Here it is with slightly puffed ZIPPY Flightmax 1800mAh 9.9V 5C LiFePo4 TX Pack .
You can find all necessary info for 3d printing this Taranis battery cover on thingiverse here, which should be enough even if you don't own 3d printer for any 3d printer service to print it for you.