Hi,
I've the fun task of verifying our battery (bq20z95 based) works with our Smart Charger in all power modes:
1) Normal
2) Sleep
3) Shutdown
Normal mode functions as expected, but testing sleep and shutdown required a little creativity. I had to discharge the cells by attaching to B+ and B- so that the gauge (bq20z95) wouldn't see coulombs disappearing without the FETs in control. I was able to verify Shutdown works as expected, but the issue is Sleep.
For reference, my pack settings are as follows:
Depleted Voltage = 8000
Depleted Recovery = 8500
CUV Threshold = 2750
PUV Threshold = 8250
Shutdown voltage =7500
Pre-chg Current = 500
Fast Charge Current = 4000
Charging Voltage = 12600
I find that if a deplete the pack cells down to around 7750mV to place the pack into Sleep and not trip Shutdown, I can charge the pack with a supply, as the CHG FET is conducting. My problem is the gauge does not request a charge from our SMBus charger. The gauge sends out voltage = 12600 (0x15) and current = 0 (0x14). The charger provides 15 volts open circuit which is loaded down to the battery voltage when the battery is connected. The current is sufficient (7 ma) to supply the gauge to bring it out of Shutdown.
My problem is why will the gauge request 0 current? Is my discharging the cells messing up the Impedance tracking and causing the zero current?
TIA,
John
