Measuring the voltage of series connected batteries

[Dreamer14388]

Thank you for your support, I appreciate that. The schematic file is attached.

[crossrulz]

Your low side of the op-amps need divided down as well.

[Henrik_Volkers]

sorry no values to read on that jpg

jpg is nice for photos but for grafics png is better....

[Dreamer14388]

I did't get you point....do you mean I should connect the same two resistor at the -ve input of the op-amp?

[johnsold]

The circuit you have drawn might work but the output signals will be rather small with realistic resistor values.

Suppose that R25 = 90 kohms and R28 = 10 kohms. Then the voltage at the non-inverting input of U3A (?) will be a nominal 4.8 V. If these are lead acid batteries and are fully charged, this voltage divider would not be acceptable because the voltage would be above 5 V. But ignore that for the purpose of discussion. If R26 and R27 have the corresponding values so that you have a differential amplifier, the gain will be 0.1 and the output voltage will be 0.48 V.  With 1 % resistors in a worst case configuration the common mode error could be 121 mV or more than a 25% error.

Also, you do not show any connections to load or charge the battery.  Those connections, which likely are required for any realistic battery test scenario, will also affect the performance of your measurement system.

Lynn

[dhruvdg]

Hi, I wanted to ask you whether the circuit attached above will work for all the same resistor values as if i keep the gain = 1 then i will obtain the accurate cell voltage which are in series

[BrandonC1]

@dhruvdg,

It looks like this thread has been dormant for about 5 years, you might want to copy relevant information and make a new post so it gets some fresh eyes on it - it is possibly the people who worked on this previously might not see that it has been bumped. 

Thank You,

Brandon C