Archer GR8 Access Rx - voltage Measurement

[David Rivers]

I am flying an electric glider with the Rx/servos powered from the ESC. 
the Archer GR8 Access receiver gives a telemetry value for Rx volts, but this is just the stabilised 5.6v from the ESC/BEC, and does not really reflect the battery voltage. 
what I would like to do is monitor the voltage of the LiPo battery so that I can see when it is getting down to a certain value. 
There is an input on the GR8 Rx called AIN2 which says it can monitor voltage in the range if 0 -3.3v via an external device. 

Does anyone know how to use this to monitor a 3 or 4s LiPo? 
 

 

[EarlyBird]

T9 have this

 

lipo volts

 

Looks good to me.?

[David Rivers]

Ok thanks. This looks like you plug it in to the balance lead of the LiPo and feed it in to the smart port on the Rx. 
 

Do you know what the AIN2 input is on the Rx?

[EarlyBird]

At a guess it is an Analogue Input 0-3.3v also at a guess voltage dividers could be used to scale down from higher input voltages.

 

But I am only guessing. ?

[Andy Gates]

Use a voltage sensor plugged into your receivers smart port (I suspect that is what the link EarlyBird has linked to).

Depending on your transmitter, you can display or read out the pack voltage as well as the individual cell voltages.

There are circuit diagrams available to be able to make a divider to use the input you want to use but it will be far  easier / lighter to use the pre made sensor.

 

I have a Jumper T16 Pro and use the ACCST version of the G-RX8 with the mini lipo sensor which is great.

You can also daisy chain a GPS sensor to it which will give speed read outs and if you log the flight, you can overlay your flight on something like GoogleEarth to see how far you have travelled and if you have flown over / into no fly zones.

 

Just checked the link and that is exactly what I use in both my gliders and some of my planes, 2 of these will not daisy chain to monitor 2 packs - you have to use the more expensive ones to do that.

Edited May 4, 2021 by Andy Gates
additional info

[Mike Blandford]

To use the Ain2 port you just need a resistor divider on the output of the LiPo. FrSky made one for the D8 receivers, which also have an AIN2 port, called the FBVS-01. Robotbirds have them in stock.

Alternatively you could make up on of your own. I've used this circuit: https://openrcforums.com/forum/viewtopic.php?f=95&t=4293&p=60766&hilit=vsense.png#p60766. This is suitable for up to a 3S LiPo (it measures up to 13.3V). For a 4S LiPo, change the 10K resistor to a 15K resistor.

You will need to configure the sensor scaling in the Tx. Set it to 13.3V for the 10K resistor and 18.3V if you use a 15K resistor.

 

Mike

[PatMc]

What Mike says this is the FBVS-1 The instructions suggest up to 5s lipo/19.8v (which by my reckoning would be 4s) I use a couple of these with D8 Rx's & pre lipo ESC's.

I don't think T9 stock them, mine were from RC-Life but they're out of stock.

[Andy48]

I would suggest a current sensor like this would be far better. If you are using OpenTx, you can set this to calculate the consumption. Voltage sensing only gives you a very rough indication of the charge level left, temperature will make a difference for instance. This device will give you a very accurate readout of the actual current used. You can then program the tx to give audible warnings when certain consumptions are reached, or program a switch to give you a readout.

 

[Frank Skilbeck]

For electric gliders the SM Modelbau Unisens E sensors are an attractive option, current, mah used, pack voltage, vario, height (and motor rpm) all in one small neat unit. And they work on just about all the main radio systems, so if you change in the future they change with you.