Other Parts Discussed in Thread: BQ24004, BQ24005
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.
Shown above is the physical circuit disconnected from power
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
Just showing that 110 mA charging current above.
Any help would be greatly appreciated
Thanks,
Ryan Amyette
