Other Parts Discussed in Thread: BQ25798
Hi,
I'm trying to test out the BQ25798EVM for charging my LiFePO4 1S battery (Charging Voltage 3.6). Most of the time when I enable charging, it would directly raises the VBAT_OVP flag (potentially VSYS_OVP) also and stop charging. This occurs when the battery's voltage is no where near its Charge Voltage.
[The picture below is measured at the TP20 VBAT when the chip stop charging and VBAT_OVP flag is high. The battery's voltage is 3.24V, but there are spikes occationally the brings the voltage over my charging voltage. During charging, the measured signal is completely flat without any spikes riding on it]
After a while it will toggle back to charging (VBAT_OVP cleared) then switch off charging right after (VBAT_OVP back on).
I tried reducing my charging current limit down to 0.1A then slowly ramping up the current limit. It seems to fix the issue, but it seems increasing/setting the current limit higher than the source (solar panel) can generate will also trigger the VBAT_OVP flag. Also, ramping it too fast would still trigger the VBAT_OVP and the only way to clear it is to reduce the current limit back to 0.1A.
[Pictures below show how changing the current limit from 0.15A to 0.2A triggered the VBAT_OVP during charging]
Is there a way for the BQ25798 to correct itself (goes to charging cycle) without the need to be controlled/intervened externally through the I2C (ie ramping up the I_lim)?
Another issue I encoutered is when the power output from the solar panel drastically changed (covering the solar panel with a blanket or removing the blanket from the solar panel while it's facing the sun), the EN HIZ will be auto enabled which stops the device from charging.
Could someone explain why this is happening?
After I manually cleared the EN HIZ, the device will directly goes to VBAT_OVP_STATUS and stop charging because the charging current would be too high and would trigger the VBAT_OVP.
