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Inaccurate voltage telemetry wit Brain 2, Hobbywing 60A, Spektrum SRXL2

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ludvigh.karoly
(@ludvigh-karoly)
Active Member Customer
Joined: 5 months ago
Posts: 10
Topic starter  

Hi There!

I have been flying with Brain 2 for a few month, and it is a very good expereince, awsome desktop app, superb support. The only thing i was not able to solve and find any solution to on the forums, is that whatever I do my voltage telemetry always show 0.5 volt less ovarall pack voltage, than it should, which is a lot. Is there any way to calibrate the readings? Im also not sure if it is even a Brain issue, or simply the Hobbywing ESC gives wrong readings.

 

Thanks!


   
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BrainDev
(@customercare)
Reputable Member Admin Registered
Joined: 4 years ago
Posts: 863
 

The FCUs receive the numeric volts value from the digital telemetry packet sent by the ESCs and do no processing of the value, they use it for Real Time logs for Recorded Flight Logs, for checking the battery voltage at power-up, and re-enter it within the telemetry packet provided for the type of protocol used by the connected receiver.
Based on what do you say the voltage is lower than 0.5V?
If you measure the voltage with an instrument it could be the instrument you are using that is out of calibration. Or the problem is just due to the fact that you measure the battery voltage at no load with circuit open, while the ESC measures the battery voltage with the motor load dropping the voltage.
The battery cables, ESC cables, and the battery-side and ESC-side connectors also have even the slightest resistance that causes a voltage drop that is greater when the applied load is greater.


   
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ludvigh.karoly
(@ludvigh-karoly)
Active Member Customer
Joined: 5 months ago
Posts: 10
Topic starter  

@customercare 

Hi, and thanks for the amazingly quick answer. I wrote the 0.5 volt error based on multiple different cell checkers (using on the balance lead), and I have also tried two different multimeters(checking at the XT60 connector ESC side), when the battery was connected to the ESC and the all the system was on, but obviously not under load. So basically I get 24.4-24.6 volts on my Spektrum, when a freshly charged battery is connected, and around 22.2-22.4 after flight (no load), when the cell checker shows 22.8, and after disconnecting the battery the charger also shows 22.8.

Maybe it is the cables and the connector, but Im not sure how i can make it better, since it is a perfect solder, with the shortest cables possible.


   
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BrainDev
(@customercare)
Reputable Member Admin Registered
Joined: 4 years ago
Posts: 863
 

Even if you read the same voltage values between chargers and multimeters, always consider as a rule of thumb that chargers have charge holding voltages on their outputs that even if they have a very low output current, due to the internal resistance present in any battery pack and connectors and wires resistence, can raise the actual voltage value compared to the measurement made with the circuit open and disconnected using a multimeter.

Consider that the measurement made by ESCs is not a precision measurement and that all ESCs have their own tolerance that varies from ESC to ESC, model to model, and brand to brand.
You can still use the value not as an absolute value but as a reference value to compare with telemetry values from previous flights.


   
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ludvigh.karoly
(@ludvigh-karoly)
Active Member Customer
Joined: 5 months ago
Posts: 10
Topic starter  

@customercare Fair enough, thanks again!!!


   
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