Part Number: BQ2057W
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Using the above circuit, I made my own battery charger using the BQ2057W to fulfill part of a school project. The battery we are using is charging, however at a vastly different rate than calculated. In the test circuit I was using, my Rsense value was .062 mOhms. The weird part was that I was only getting a 6 mOhm drop across this resistor, resulting in a charging current of only 100 mA, compared to the calculated 2 A charging circuit I was supposed to be getting. I do not know why the resistor is dropping this amount of voltage when it should be held consistent around 120 mV. I have used a couple other different sense resistors as well, including a 125 mOhm resistor, and have been getting similar strange values. Shown below are the voltage values I measured across all the pins,
10 V - Vcc
10 V - Vcomp (I disabled this pin)
7.63 V - Bat
9.87 V - Vsns
9.11 V - CC
4.98 V - Tss (Also disabled this pin)
.006 V - Across resistor
Bill Johns had been helping me with a previous question, and recommend using a couple different ICs including the BQ24004. I have ordered this part, but am still waiting and do not know when it will arrive. I had previously ordered the BQ2057W before I became aware of these parts and have been trying to get it to work just in case the part does not arrive in time. Below is the physical circuit on a breadboard that I've been using to test, please let me know if you need any more information, any help would be greatly appreciated.
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Shown above is the physical circuit disconnected from power
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Shown above is the circuit connected to power. LED is on, and battery has shown progress in charging so circuit is working. Just not getting current output that I was expecting
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Just showing that 110 mA charging current above.
Any help would be greatly appreciated
Thanks,
Ryan Amyette
