Hi,
I would like to use mp2722 for battery management in my project. I’m looking for some way of reading battery level - battery charge percentage. Is it possible to this using just mp2722? or do I need some additional IC/device or read battery level by my micontroller? What do you recommend?
Hello David,
MPS has some dedicated Fuel Gauge solutions in order to read, voltages, currents, and battery percentages, but unfortunately these are only compatible with applications with 2 - 16 cells and the MP2722 is a single cell application.
However, there are indirect ways that you can estimate and determine your battery percentage state of charge (SoC). One indirect method is voltage-based SoC estimation, which estimates the SoC based on the battery’s open-circuit voltage (OCV). OCV is the voltage across the battery terminals when it is not connected to any load.
The Open Circuit Voltage can change with the SoC, but the relationship between OCV and SoC is nonlinear due to the aging and temperature of your battery being added variables so this method can vary in accuracy.
Another indirect method is impedance-based SoC estimation, which estimates the SoC based on the battery’s internal resistance. The internal resistance of your battery increases as the SoC decreases, so measuring the resistance can give a relative estimate of the SoC. You can characterize this method by measuring the impedance at different voltage levels.
Hope this helps.
Best,
Krishan
Hi, thanks for your replay.
You mentioned about OCV circuit. however in my application battery is going to be connected all the time via MP2722. Load is also available all the time, because Vsys is used to feed my application together with main uC (microcontroller).
I was thinking about just measuring voltage of battery together with load via uC ADC channel.
I hope that it will be less accurate than OCV but still will give me some knowledge about battery level. Is it correct understanding?
I suppose if you did the same sort of thing with the loaded voltage and measuring impedances at different SoCs for characterization, then this would roughly get you the same sort of SoC estimation you are going for.
See if this form of characterizing SoC in your device is as accurate as you desire. At the end of the day all of these methods that I have listed are just estimations, each with their margins of error. Hopefully this is close enough to meet the desired results of your application.
Best,
Krishan