# How to determine Voltage Multiplier and Amps/Volt in QGroundControl?

Hello,

I’m new to drone configuration and am right now trying to reconfigure my Battery Monitor reading on QGroundControl, but I do not know the voltage multiplier nor the amps/volt. The application says to just measure the voltage of the battery and the current draw from the battery with the motors not running, but using these values results in nonsense readings when looking at the telemetry data expressing these two values.

So, I tried to follow the steps of this thread: Power Monitor setup on ArduPilot Copter 3.6+

He says that the voltage multiplier and amps/volt are provided by the manufacturer of the power module of the drone. And looking at his link for his power module, it does not clearly state his two values. My power module (Web Store) doesn’t seem to state this either. To compensate, I guessed and checked my way to the “correct” voltage multiplier by changing it until I got what I knew what the battery voltage, and I calculated the average current draw (total current draw when drone is hovering). However, I am very uncertain about using these values.

So, how to do I either accurately calculate the voltage multiplier and the amps/volt or find the values given by the power module?

(For reference if needed: Battery Voltage is 22.7V, 30000 mAh, current draw with no motors on is 0.30A; let me know if any other information is needed)

This will be wildly inaccurate. The easiest way to set the amps/volt value is to fly a fully charged battery and from the flight log note the consumed mah. Then re-charge the battery and note the charged mah. Then calculate a new amps/volt value by:
New amps/volt=(old amps/volt*charged mah)/logged mah

Do this a couple times and it will be close enough for all purposes.

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By “charged mAh”, do you mean the amount of mAh gained after the charge (After flight: total capacity - capacity left), the full capacity itself, or something else? If it’s either of the first two, I’m confused as to how that would that help determine the amps/volt?

If the charged mAh is the latter, then the new amps/volt would shoot off to infinity eventually (charged mAh/consumed mAh => battery capacity/consumed mAh would always be a positive number).

If the charged mAh is the former, then how would that calculation do anything at all? A fully-charged battery loses some mAh and then regains it by charging, so charged mAh is equal to consumed mAh always, changing nothing.

What the battery charger put back in the pack to fully re-charge it. It’s not complicated.

I have a craft with a amps/volt value of 54 and it logged 1750 mah consumed for the flight. I charge it and the charger puts 1990 mah back in. So the amps/volt is wrong. The calculated new value is 61.4. That’s it…

So you have the Mauch BEC - do you also have the Mauch current sensor?
If you do, it will have come with a paper detailing the voltage and current settings.
The typical Mauch settings will be about 10.0 for voltage divider and about 50 for the amps per volt.

You can use this procedure to test the current measurement accuracy.

• Start with a fully charged battery and hover for quite a while to use up a good proportion of a battery pack, land and immediately and charge the battery, note how much mah the charger put back in.
• Examine logs and see what “milliamp hours” Ardupilot thought you used at {existing} Amps/volt.
• New Amps/volt = old amps/volt x charger mah ÷ logged mah
• perform several flights like this to fine-tune the value after each flight
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