Tool/software:
Hi Everyone
I am currently designing a battery powered device and want to accurately determine the state of charge for the battery. I am looking at using the BQ28Z610 for this purpose.
My question is regarding the selection of a sense resistor for the design. The datasheet recommends the use of a 1-3 mOhm resistor. As I understand it, the main consideration is to keep the voltage drop across the resistor within the measurement range of the ADC (125mV). For my application I am planning to charge the battery via a small solar panel or an external power supply. I have already implemented this in a previous version. This means that my charge current will range from a few milliamps to a maximum of 2A according to the conditions and whether or not the external charger is used. The device itself uses about 70mA when operating.
Since the current will be relatively low, I am afraid of even using the maximum 3 mOhm sense resistor, since the voltage drop will be very small and far below the 125mV range.
Is it OK for me to use a much larger sense resistor that will make use of more of the measurement range? If I work with a maximum of 100mV and my maximum current is 2A, I was thinking of using a 50 mOhm sense resistor. Any recommendations will be most helpful.
