RC India

I think Tx battery might be of specific voltage (11.1v 3S ?) and dimensions that is designed to fit in the Tx battery compartment.
Can't all other LIPO batteries 2S, 3S, (considering the power requirements) be used as receiver batteries with ESC?
Are there any other electrical differences that need to be considered?

I am confused because on some online stores, some batteries are specified as "Rx batteries". I can understand specifying a battery as Tx battery. but why is it required to specify a battery as Rx battery?

Most receivers and related electronics work at 6V (some older ones can only handle 4.8v, and some newer ones can handle 8v and above).  So typically you use 2s lipos for RX as their fully charged voltage is 8.4v, but with a voltage regulator (not ESC) that brings the voltage down to 6V.  You can use higher cell count lipos, but your regulator has to be capable of dealing with that and bring down the voltage back to 6v.  On many voltage regulators, the choice for output is 5.1v or 5.8v, which can be selected using a jumper.

The other difference is that receiver packs (and TX packs) do not need high discharge rates, so they are typically around 3C only.  They are also physically smaller to fit into tight spaces within fuses.

Thanks Anwar.

so if a ESC contains a BEC, can we use a single battery on a plane that can power receiver as well as motors/servos ..?

Of course. That is what most people do.  But then the whole question of RX batteries go away.

Using separate/external BECs has some advantages. 

BTW, I used the term voltage regulator in the earlier post, might as well have said BECs. 

Thanks, that was infact the confusion for me. I had assumed that only a single battery is used on the plane (which supplies power to both receiver and motors, servos) and that the battery specification (cells, C rating etc) was decided based on motor/prop used. I was not aware that separate batteries are also being used on planes.

Receiver batteries are a must in fuel powered planes. 

For electrics, you usually have the obvious choice of using the "internal BECs" in most ESCs. People opt for using "external/standalone BECs" for reasons like [1] to reduce heating of the ESCs, [2] to have control of the aircraft for a safe landing even when the main lipo runs out of power, etc.