Srry for the unclearexplanation of my problem, I'll try to give a better one.
The purpose of this circuit is to both being able to measure the internal resistance of the cell, as well as testing the capacity. I want to create a circuit that can be fully controlled by a microcontroller so it can be automated.
Both requires you to know the current running through the resistor. Most people I've seen uses two analog pins to measure the voltage on each side of the resistor compared to the ground.
I'm trying to see if you can make a shortcut and only use one analog pin.
Here is a circuit similar to the first one I posted.
Since the Arduino have the same common ground as the cell would you really need the A0 pin?
To getthe Voc (open circuit voltage):
-D13would beLOW, to allow no current through the mosfet
- Then the Voc can be measured with A1
Then to get the Vwr (Voltage with resistor):
- D13 would be HIGH, to allow current through the known resistor
- Then the new voltage Vwr would also be measured with A1
Since the Arduino and negative terminal of the cell are both grounded, the measured A1 voltage would be equal to the voltage drop over the resistor. This should only work because the voltage is measured arecompared the ground, if they weren't grounded I would guess you need both A1 and A0.
So this would be the final circuit which should be able to measure both internal resistance and the capacity:
It seems to make sense to me, but the fact that everyone uses two analog pins for this circuit,makes me thing I'm wrong.
watts-on said:
As I understand it, the most accurate way to measure IR is using two different value resistors and calculating based on the differences between the readings.
Julian Ilett did an interestingvideo....
That is actually interesting how he uses two different resistors, wonder what the accuracy of that is?
I've seen people also sending a high frequency pulse through the cell, but for me it doesn't really matter as long as the results are consistent.