Wrong Values @ 0.001Ohm Shunt, value overrun?

[Jim4Beam]

Hello,

I am using the INA219 and this nice Library at a 24V Battery System (20V to 27V) at a 0.001Ohm (1milli Ohm) Shunt with a current of +30A (charging) and up to -120A (discharging).

Please find my Code attached/below.

The measurement of voltage above 16V is working due to the changes of “unsigned int temp;” to “int temp;” in “float INA219::busVoltage()// returns the bus voltage in volts ” in file INA219.cpp. (described in Issue #3)

But I still have problems with the measurement of the Current and Power values.

When I apply 25.1V and -5.2A (is -5.2mV at the shunt, measured with multimeter) I get the following results:

---

raw shunt voltage: 697

raw bus voltage: -15166

shunt voltage: 3.9000 mV
shunt current: 177.5542 mA
bus voltage: 25.1720 V
bus power: 4468.9951 mW

Does it my be a problem of value overflow? What might be the problem?
Thank you very much.

I have set the following default settings in INA219.h:

define D_I2C_ADDRESS 0x40 // I2C Adresse(64)

define D_RANGE 1 // 0: 0-16V, 1:0-32V

define D_GAIN 3 // Range: 2: +-160mV, 3: +-320mV

define D_SHUNT_ADC 10 // ADC 3: 12-bit, single sample, 532uS conversion time 6:8x 4,2ms

define D_BUS_ADC 10 // -||-

define D_MODE 7 // 7: continuous conversion

define D_SHUNT 0.001 // R-Shung [Ohm]

define D_V_BUS_MAX 28 // U-Bus-Max [V]

define D_V_SHUNT_MAX 0.160 // U-Shunt_Max exp. [V]

define D_I_MAX_EXPECTED 130 // I-Max exp. [A]

My Code:
/**********************************************

• INA219 library example
• 10 May 2012 by johngineer
• this code is public domain.
  **********************************************/

include <Wire.h>

include "INA219.h"

INA219 monitor;

void setup()
{
Serial.begin(115200);
monitor.begin(64);
// U-Range 0: 16V, 1:32V; I-Gain 2: 160mV, 3: 320mV; Bit/Avr U; Bit/AVR I; D_MODE 7: cont.
monitor.configure(1, 2, 10, 10, 7);

// Shunt[Ohm]; max Shunt [V]; max U [V]; max ecp. I [A]
monitor.calibrate(0.001, 0.160, 30, 130);

}

void loop()
{

Serial.println("******************");

Serial.print("raw shunt voltage: ");
Serial.println(monitor.shuntVoltageRaw());

Serial.print("raw bus voltage: ");
Serial.println(monitor.busVoltageRaw());

Serial.println("--");

Serial.print("shunt voltage: ");
Serial.print(monitor.shuntVoltage() * 1000, 4);
Serial.println(" mV");

Serial.print("shunt current: ");
Serial.print(monitor.shuntCurrent() * 1000, 4);
Serial.println(" mA");

Serial.print("bus voltage: ");
Serial.print(monitor.busVoltage(), 4);
Serial.println(" V");

Serial.print("bus power: ");
Serial.print(monitor.busPower() * 1000, 4);
Serial.println(" mW");

Serial.println(" ");
Serial.println(" ");

delay(1000);

}

[Jim4Beam]

Any thoughts?