Hello.  
Can you help me with a question? 
I'm building an RC car that follows the same philosophy as an RC plane. It has the receiver that controls the servos and the esc. 
The battery powers a voltage regulator (which powers an analog fpv camera) and an ESC (which powers the receiver via the BEC). 
It turns out that I don't know how I send the battery voltage data to myself. The receiver sends its voltage, but as it is connected to the BEC the voltage will always be 5v. How do FPV cars and planes transmit battery voltage to the pilot?

I have a Flysky FS-i6X receiver and transmitter, I'm planning to use this ESC.

Some receivers have sensors that can be attached specifically for detecting voltage, I think Frsky had that and you would hook up the voltage sensor from vbat to the RX's smart port, not sure if Flysky has something similar.

It maybe easier to overlay the voltage onto the analog FPV video feed instead, which is often referred to as OSD (on screen display). Some cameras will have this built in, I think Foxeer has some with an extra pin that you connect directly to vbat. Otherwise some VTXs may have it, and there are OSD boards that go between the camera and VTX for the same purpose, but these are pretty rare these days as OSD function is integrated into most Flight Controllers used for drones/planes.

(26-Jan-2024, 11:11 PM)mstc Wrote: Some receivers have sensors that can be attached specifically for detecting voltage, I think Frsky had that and you would hook up the voltage sensor from vbat to the RX's smart port, not sure if Flysky has something similar.

It maybe easier to overlay the voltage onto the analog FPV video feed instead, which is often referred to as OSD (on screen display). Some cameras will have this built in, I think Foxeer has some with an extra pin that you connect directly to vbat. Otherwise some VTXs may have it, and there are OSD boards that go between the camera and VTX for the same purpose, but these are pretty rare these days as OSD function is integrated into most Flight Controllers used for drones/planes.

My vtx doesn't have an on-screen display, I'm going to look for OSD boards. As for the rx, it has voltage telemetry, but it shows the voltage it is receiving to work, which in my case, is the voltage regulated by the ESC (fixed at 5V).

Thanks. I will research these methods.

I used a flight controller in mine, so it ended up working just like a quadcopter would. Definitely going to be reading the other answers though since I have an interest in dipping my feet into other configurations and would really like to know more. While I could just put a flight controller into a rover, that adds cost.

i believe sanva or futaba would provide telemetry information like voltage


you can add a lipo buzzer directly to the battery, it beeps on a set voltage. that was what i used on rc car to save undervpltage on the lipo. modern esc rc car escs does detect the lipo voltage and get in a slow mode or stop beforbundervoltage by itself.

do you need live voltage displayed or just a warning on low voltage?


rc planes can be so efficient, they can fly for longer than needed. once checked the lipovoltage in a few flights, a time warning does the full job to prevwnt the lipo

Ok, let's go in parts... I would like to have access to the current battery voltage, either via the video feed or via the remote's LCD.

After some research I discovered that some receivers allow sending telemetry (some need an external module connected directly to the battery), so you can connect the measurement module to the battery and then connect it to the receiver's telemetry pins.
Another option would be to use an OSD (On Screen Display) board between the camera and the vtx to present this information. A sensor capable of measuring voltage would be needed to send the voltage to the OSD.

This is what I understood with the information given above and with other information I took from the Discord server, so here is the summary.

You didn't mention which model receiver you are using and what battery voltage you are running. Some Flysky receivers are rated to higher voltages and if your battery is within that range you might consider powering the rx directly by the battery.

Also if you want it in your FPV feed, some Foxeer cameras will apply the voltage to the OSD in camera. I believe Predator 5 has a Vsens pin for connecting to the lipo for that purpose, and Toothless 2 can be powered up to 16v also will display camera voltage.

(01-Feb-2024, 12:02 AM)mstc Wrote: You didn't mention which model receiver you are using and what battery voltage you are running. Some Flysky receivers are rated to higher voltages and if your battery is within that range you might consider powering the rx directly by the battery.

Also if you want it in your FPV feed, some Foxeer cameras will apply the voltage to the OSD in camera. I believe Predator 5 has a Vsens pin for connecting to the lipo for that purpose, and Toothless 2 can be powered up to 16v also will display camera voltage.

The receiver is "FS-iA10B". I already have an analog camera that doesn't have an OSD, so I would need an OSD board if I choose to transmit video.

The specs says your receiver will take up to 8.4v, so if your car is using batteries within that voltage range (2S) then you could power the receiver directly off the battery and use your radio telemetry (if that receiver transmits voltage telemetry).
https://www.flysky-cn.com/ia10b-canshu

an fpv analog cam with osd and voltage sensor like a "foxeer nano predator" would provide good voltage readout up to 6s voltage.

The Radiomaster MT12 is able to display voltage when using ELRS with the correct eeciever. I use an ER5c-i on my FPV crawler. Along with seeing the voltage on my radio display I have a button to tell me me current voltage.

It maybe easier to overlay the voltage onto the analog FPV video feed instead, which is often referred to as OSD (on screen display). Some cameras will have this built in, I think Foxeer has some with an extra pin that you connect directly to vbat. Otherwise some VTXs may have it, and there are OSD boards that go between the camera and VTX for the same purpose, but these are pretty rare these days as OSD function is integrated into most Flight Controllers used for drones/planes9apps apk

I'm a little late to the conversation but maybe this will help?

This is Ronin's design and is a good starting point.

I used this for my basic design, but I don't have a diagram for my changes.