Lipo Balance Charger/Protection Question

[braden_sun]

Hi all,

I am trying to fully understand the following BMS circuit that includes balance charging and protection: https://github.com/ZOUDIO/BMS345. The protection IC is the TI BQ77915 and the charger IC is the TI BQ24650. I have a couple questions about how these circuits work and fit together.

1. From the BQ77915 data sheet it states "An OV fault detection occurs when at least one of the cell voltages is measured above the OV threshold, VOV for a time of OV delay, tOVn_DELAY. The CHG FET is turned off." and "The state comparator is turned on when CHG is turned off. If a discharge current is detected, the device immediately switches the CHG back on." I thought current flowed from the drain to the source on a mosfet so if the CHG fet is turned on when a discharge current is detected, wouldn't current be flowing in the direction to charge the battery? I would have thought that the CHG fet is on during UV and DSG fet is on during OV? (See figure 3)

2. For the BMS circuit where the charger IC,  protection IC and load are connected together on the Pack+ and Pack- terminals, when the charger IC kicks on to charge the battery, the load would be powered off the charger IC and not the battery correct? So you need to account for the current consumed by the load when choosing the charge current? (See figure 1 and 2)

Thanks for the help!