Wow. Just wow. Thank you for doing this.

I will note that at 3.5V you have only used about 850mah of the Vapcell F14 (extrapolating the amp draw from the run time data and reviews for the cell). I would recommend running them down to 3.0V per cell and you should be getting a pretty consistent 1300mah out of them, with a decent buffer as the 1400mah rating is reached at 2.5V You can also get them with a button top. Vapcell are legit batteries and have gained some good reputation over the years, there is counterfeits out there so be mindful.

Get the battery tray that comes with the RM TX16s You can use (2) 18650 rechargeable batteries "button top" in the battery tray and hot glue it lightly to the cover of the module cover door

3.5v is not even 50% of the capacity in li-ion cells and all cells have slightly different curves between 3.8v and 3.0v. Some cells have a quicker drop to that 3.5 mark and then the curve flattens before reaching 3.0v and dropping rapidly. Some cells have fairly flat curves from 3.8v to 3.5v and then have a faster drop off from that point to 3.0v. Unless you're testing until you get a battery warning or the radio shutting off, the test isn't giving each cell a chance. Regardless, just a simple battery capacity tester will show how much capacity is actually in each cell.. just test the current draw at whatever the radio runs at plus 250mw for the transmitter.

Good to know about that battery, I've been looking for a good one for the hdzero goggles so I will avoid. I am really hoping radiomaster will come out with a v2 zorro which takes 18650 li-ion batteries.

Is there no other brand name battery that fits the zorro…..I tried to order the radio master batteries but Banggood said the batteries don’t ship to my region?? Doesn’t make any sense.

Do you have to remove the 18350 batteries when using the external battery ?

I have doubts, we can use powerBank and power through USB c, will it work?

Be very careful suggesting mods like these...for example in Europe, if you modify your remote like this you will violate your insurance....and this is a serious act if you do happen to crash your rig into someone and there is an investigation which looks at your equipment. NB...Only ever do recommended and suggested mods from the manufacturer itself......and never recommend anyone to open their TX and solder onto any PCB board inside....hope this helps.

I found Keeppower batteries that are rated for 1200 mah and they use a magnet to make it a button type battery. I get what you get between the 1100 and 1400 and you don’t have to solder. Actually I believe you could put a small magnet on the 1400 battery.