Hi,
I designed my first smart battery circuit based on the BQ40Z80
Unfortunately, I found a problem on the board on this
first production: I reversed SRN and SRP. (look the schematics).
I tested the circuit in the nominal way, connecting the thermistor and trying some cycles of charge and discharge, obviously with the complementary behaviour. (During the discharge, the gauge increased the RSOC).
I tried to enable and disable the mosfet and everything worked (a part the sign of the current).
To recover this problem I thought to invert the BAT(-) with PACK (-) connection in this way:
Battery (+) connected to BAT (+) terminal [2 x Li-ion 3.6V]
Battery (-) connected to PACK (-) terminal.
Power source (+) connected to the PACK (+) terminal and set to 8.2V.
Power source (-) connected to BAT (-) terminal.
At the beginning was ok, the circuit behaviour was perfect.
I charged the battery until 2 amperes without problem (but not until the end of charge set on 50mA). I also tried the discharge.
But when I tried to fully recharge the battery, near the end of charge (between 100mA and 50mA), the circuit started a sort of ringing, opening, and closing the mosfets and then they broke. For sure I lost the internal diodes. The temperature of the whole circuit increased a lot.
I retried with a new circuit in the same configuration (inverting BAT- with PACK -) and I had a similar problem breaking the internal diode of the DSG fet.
Do you think that this workaround is related to these failures?
Another very very strange thing was the voltage on the gate of the CHG mosfet: 18.5V. I have no sources at this value!
Batteries: 7.2V
Power supply: 8.2V
