Solved Minimum Lipo alarm setting for telemetry

[TheFlyingBrit]

Planning to set up an alarm on my telemetry to warn me when my Lipo battery is getting low (not critically low). As a rule of thumb, I was always under the opinion you should go off 3.5 volts per cell. Therefore, a 3s would have a minimum voltage of 10.5 volts, that would be a land the plane now alarm ?
Based on your experience what voltage value would you use as a first alarm for a 3s lipo ?

 

[The Hangar]

I try never to run my batteries below 3.7 volts per cell to help with longevity of the packs. That being said, I set my alarm for 3.4 or 3.5 volts since the voltage will sag under throttle.

 

[TheFlyingBrit]

So a 3.7 volt stage 1 (warning alarm), with a 3.5 volt stage 2 (low alarm) sounds realistic

 

[The Hangar]

So a 3.7 volt stage 1 (warning alarm), with a 3.5 volt stage 2 (low alarm) sounds realistic

Yes, that sounds great! I use the cheap alarms so unfortunately I don't have that option haha...

 

[TheFlyingBrit]

I can program it in my TX16s using OpenTx
By setting up a Logical switch function a<x using the VFAS reading in the Telemetry where the value is 11.1v.
I can then set up a special function that acts on the logical switch to play the VFAS value when its less than 11.1v (3.7v per cell)
I can then do the same again with another logical switch, but use the 10.5v value and play a sound "Battery Low" or "Battery critical".
So when the battery value goes below 11.1v it says the value, but if it drops below 10.5 I get an audible warning "Battery Low".
Sounds more complicated than it actually is, plus you need to add delays etc to read out.

 

[TheFlyingBrit]

Quick update, I have set up two alarms on my transmitter first being a voltage reading when my flight battery is low. The second is a verbal waring that tells me the flight battery is very low (time to land).
The programming was easy took less than a minute & half to complete. The down side I wanted to get VFAS voltage value from the Lipo battery but this wasn't available on the built in telemetry. At the moment I only have RX battery voltage which I assume is the voltage supplied by the Lipo to the receiver via the ESC/BEC.
I have a 5.5v supply using a 1500mAh 3s, therefore I set the first alarm to trigger at <5 volts. The second alarm triggers when the voltage drops below 4.8 volts.
Guessing I will need to buy one of these external FRsky voltage sensors that connects to the balanced lead of the lipo and the smart port of the receiver. That should give me the reading I want.

FrSky FLVSS LiPo Voltage Sensor with SMARTPort
This is a new sensor designed and developed by FrSKY to collect important flight information and performance data which can then be transmitted via the SMART PORT of telemetry-enabled receivers such as X8R, X6R, X4R, etc to FRsky Transmitter.

 

[Taildragger]

Quick update, I have set up two alarms on my transmitter first being a voltage reading when my flight battery is low. The second is a verbal waring that tells me the flight battery is very low (time to land).
The programming was easy took less than a minute & half to complete. The down side I wanted to get VFAS voltage value from the Lipo battery but this wasn't available on the built in telemetry. At the moment I only have RX battery voltage which I assume is the voltage supplied by the Lipo to the receiver via the ESC/BEC.
I have a 5.5v supply using a 1500mAh 3s, therefore I set the first alarm to trigger at <5 volts. The second alarm triggers when the voltage drops below 4.8 volts.
Guessing I will need to buy one of these external FRsky voltage sensors that connects to the balanced lead of the lipo and the smart port of the receiver. That should give me the reading I want.
View attachment 197445
FrSky FLVSS LiPo Voltage Sensor with SMARTPort
This is a new sensor designed and developed by FrSKY to collect important flight information and performance data which can then be transmitted via the SMART PORT of telemetry-enabled receivers such as X8R, X6R, X4R, etc to FRsky Transmitter.

Is your pfp your finished edge? It looks beautiful.

 

[KubKade]

Planning to set up an alarm on my telemetry to warn me when my Lipo battery is getting low (not critically low). As a rule of thumb, I was always under the opinion you should go off 3.5 volts per cell. Therefore, a 3s would have a minimum voltage of 10.5 volts, that would be a land the plane now alarm ?
Based on your experience what voltage value would you use as a first alarm for a 3s lipo ?

3.8 volts is the best storage charge. However after you disconnect you lipo and let it cool it will climb about .1 volts so essentially you could go with 3.7.

 

[TheFlyingBrit]

Is your pfp your finished edge? It looks beautiful.

The Avatar is the finished FT Edge, but a good friend of mine pointed out it was missing some decals compared with the Precision Aerobatics version I used the colour scheme from. The side force generators look a little bland (the original plane had PILOT on them and JVC ), I have to agree with him but my eyes and painting fingers need a few days to recover before I tackle anymore decals.

 

[TheFlyingBrit]

3.8 volts is the best storage charge. However after you disconnect you lipo and let it cool it will climb about .1 volts so essentially you could go with 3.7.

I am going to buy one of the FLVSS sensors they work out around £18 (that's approx $25). The first warning will be 3.7 volts the second I am guessing 3.5 volts per cell as the critical alarm.

 

[TheFlyingBrit]

Ended up buying 2 of those Lipo voltage sensors, the full size one in the previous post and a new mini version half the weight for lighter models.

The bigger version has an on screen display as well as sending telemetry data via the smart port. The Mini doesn't have the screen thats how they reduce the weight.
This is the mini version it cost me £17 ( that's equivalent to $23, its only $13 on Aliexpress). I bought it as part of a bulk order on Banggood, so saved on postage and got a discount.
The larger version cost me £18 from Aliexpress ( that's equivalent to $25), not much difference in price but that's down to where I bought it.