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Plane safety/ESC Low Voltage motor power down.

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Old 08-19-2015, 12:34 PM
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Truebuild
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Default Plane safety/ESC Low Voltage motor power down.

It seems that most ESC low voltage motor power down setting is 3.2v.
Is 3.2v per cell really enough voltage to power the RX and Servos to enable the pilot to land the model?

Many Lipo voltage charts have 3.2v equal to an empty cell!

I would have thought 3.5v would be a more sensible value as this seems to equate to approx 7.5% left in the cell; or even 3.68 that is 10% so the the plane could limp home.

Am I missing something?
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Old 08-19-2015, 03:29 PM
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Truebuild
Remember the ESC is seeing the cell voltage under full load. Once the motor is cut the current required for the radio and servos is much smaller and the voltage rises to maybe 3.5V or even higher which would suggest the remaining capacity is now bigger.

Measuring the remaining LiPo capacity by voltage measurement is really only a guide as the voltage depends on the current being drawn at the time.
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Old 08-19-2015, 06:32 PM
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With an LVC of 3.2 volts per cell, you should measure about 3.7 volts per cell after they have rested for a few minutes. It should not be lower than this or you risk shortening the life of the battery.

A battery that is discharged to LVC will still have plenty of voltage to drive the ESC's linear or switching BEC to produce the necessary 5-6 volts needed to power the receiver and servos.
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Old 08-19-2015, 11:40 PM
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Thanks for the replies people.
I am fully aware if the fact that the Cell voltage drops dramatically under load; however, I had forgotten about it in this instance and I thank you for pointing that out.

Most people I believe try to stick to the 20% left rule

From what you say I still feel that the low voltage setting is too low and that the LVC options should include 3.3, 3.4 and 3.5 per cell to enable the motor to go into reduced power mode.

The hobbyking dlux 70amp ESC has a matching control box that has a 3.5v cell option that I would like to try; however, the ESC only goes as high as 3.2v ;(

Does any other ESC provide a wider range of Low Voltage Cut off?
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Old 08-20-2015, 01:56 AM
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You can probably get better control of the resting cell voltage by timing your flights. I personally don't rely on the LVC setting because it is generally too low, as you have noted. Just fly for five minutes, measure the resting voltage and adjust your flight time until it's always around 3.7 volts per cell.
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Old 08-20-2015, 11:27 PM
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Default Plane safety/ESC Low Voltage motor power down.

For planes that have the space I use my Telemetry script (available at http://rcsettings.com/index.php/view...proved-version )that uses the Taranis frsky-fcs-150a-smartport-current-sensor
frsky-flvss-lipo-voltage-sensor

This telemetry lua script provides an accurate method of informing the pilot of remaining lipo percentage, complete with audible readout of each 10% drop in capacity.
Other methods that just read lowest cell voltage suffer from false readings due to the fact that lipo cells drop dramatically on full throttle then recover.
The script monitors the actual current consumed whilst flying.


Believing that you can never have enough safety features I was looking at the Low Voltage Cut out system and found that it seems to be a poor system.

Has anyone hacked ESC's (Changed the firmware)?
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