Hello,

I have ordered a VTX Eachine TX806 leaf from banggood.
Input voltage is 7v to 25v.
I want to use this VTX on a toy grade car which runs on 3V battery, so I cannot take power from the car battery.
I am planning to make 2s battery either by connecting 2 2600mAh 18650 li-ion in series or by 2 3.7V 500mAH lipo (cheap Chinese non-branded)

Which one is best suitable for my need?
Should I put a balance lead as well, so that these can be charged like a normal lipo?

Thanks

If you have 2 or more cells, balance port is recommended. Otherwise you will start to have mismatch voltage and that is not good. You can save the task of making your own pack by using a case like the Fatshark 18650 case or something similar. But you will need a charger for your cells. Oscar has a tutorial on his blog to modify Fatshark case to add balance port.

https://oscarliang.com/fatshark-battery-...rging-mod/

If you want to make your own, I put up a tutorial on how to do this. Although it is a bigger pack, the concepts applies.


https://intofpv.com/t-big-better-fatshark-pack

One other alternative is to buy protected cells. They have circuit from over charge. So you don't need a balance port. But the cells are costly.

2 Panasonic NCR18650B 18650 3400mAh 3.7v Protected Button Top Batteries https://www.amazon.com/dp/B00NUI47OY/ref...nCbWNKSKVV

Thank you for the link.
I think I will go with the battery case method, as that does not involve spot welding.
Could you please review below diagram I drawn?
Note: I could get hold off only 3 battery holder, I will leave the 3rd cell blank.

   

Looks correct.

If you are quick with the soldering iron, you can soldering instead of spot weld.