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# how to read power level of battery?

hello i have battery on helicopter and i need to read power of this battery to use it in pid gain ,i read voltage using voltage divider and calculate it and i sense current before motors and calculate power, but i dont think this is working, can you help me for that?

## Discussions

Best Answer 6 years ago

How are you reading the voltage an current? Are you using a meter or an on board micro controller?

Answer 6 years ago

on board microcontroller

Answer 6 years ago

Yes a voltage divider can be used to read voltage. You will need a shunt resistor to read current. Reading the voltage across the resistor gives you the current.

Answer 6 years ago

so i put the shunt resistor with battery terminal on helicopter and thats all, wouldnt drop the voltage on motors?

Answer 6 years ago

A shunt resistor is a 1 Ohm resistors that can handle a lot of current running through it. Won't affect the motors hardly at all.

Answer 6 years ago

A shunt resistor is a LOW value relative to the maximum current in the circuit, you can't say its "1 Ohm", it might be 0.01 Ohm in a practical circuit.

6 years ago

so i must use low resistor value for shunt and low resistor for voltage divider depend on max mah

Answer 6 years ago

ok i want the voltage divider not to pull current so i increase its value like 68k ,33k? or i need to use mosfet?

Answer 6 years ago

Yes. You may then need to amplify the voltage to the range of the ADC on your processor, or you can use some of the current to voltage sensing chips that are available like the Diodes Inc (Zetex) ZXCT10XX range (there are a load of parts with 10 in front of them.

6 years ago

so i must use low resistor value for shunt and low resistor for voltage divider depend on max mah?

Answer 6 years ago

The voltage divider values aren't as critical as the shunt resistor. Make the divider resistance >10K