Note: I've now completed my full review of the X-lite which can be found here
The Taranis X-Lite is out and it's great. I have mine and it feels great in the hand, a lot of though has gone into the detail. This is not a review, I'll get to my experiences there soon enough but I want to cover an alternative for the one downside - the uncommon size of battery required to run it.
Battery sourcing issues
I live in New Zealand and if you think you are having trouble sourcing 18500 batteries where you live then you should try it here. In fairness one of the local quad shops sells the genuine panasonic cells but at $USD25 including delivery it's more than I want to spend. Also being impatient I did some lazy research. The "18" part of the "18500" refers to the 18mm battery diameter (some where between a traditional AA cell and a C cell) whereas the 500 refers to a 50mm length - identical to an AA or C cell. Just for a laugh I tried a NIMH AA cell in either side and you know what? It powered up. Since the AA cells are the right length, there was enogh tension in the springs to make sure they stayed connected and didn't jiggle around. The AA's however are not a viable option since they only provide 2.4 - 3.0v in series. One of the rechargeable lithium battery technologies is clearly needed here in order supply the necessary 6.0 - 8.4v the controller requires.
You can use a 14500 battery
Based on the above the more common 14500 cell is viable (an AA sized battery with Lithium technology) and these are much more common than the 18500 albeit with a little less capacity. See below for how they fit in the X-Lite:
Get a pair of batteries for less than USD$8
If you live in Australia or New Zealand the cheapest place you can get a pair of these is actually Bunnings Warehouse - see below for the picture but there are the Solar Magic 3.2V 600mAh 14500 Lithium Batteries 2pk and are only $11.98 in NZ (here) or $9.98 in Aus (here). They are based on LiFePO4 Chemisty meaning they put out 3.2V per cell which is fine for the X-lite. Below is a picture of the battery pack and also a picture of it successfully powering the X-lite:
Considerations for LiFePO4 batteries
Since the chemisty of these batteries is slightly different to Li-Ion or Li-Po that we are more familiar with, I changed the voltage range from 6.0 - 7.0v with the warning coming on at 6.0v. Charging these at 3.5V will get you to 95% capacity and 3.65v will get you to 100% capacity. Do not charge higher than this!!! I'd recommend charging to 3.5V only for safety. There is a good article here on what to expect with voltages and charging on this type of battery but in short it looks like it is well suited to this application.
Continuing with the NZ/Aus theme you can pick up a battery box for only $1.50 from Jaycar here or alternatively you can find one at Banggood here. than can be easily adapted to a balance charger for you to safely charge the batteries on you Lipo charger (don't forget the voltages above). Below is a picture of the battery box and how to adapt for balance leads.
It's early days yet but it's working well in the controller. Not sure about the heritage of these batteries so next time I charge I'll see how much capacity they take. For $10 for 2 batteries I didn't need to wait for though it is a good option.
Gearbest were kind enough to provide me this Taranis X-Lite to review so I'd encourage you to purchase from them if you are considering one. It only took 3 days to arrive to me in NZ so not bad with ragard to delivery speed. It is available here in either black or red.