BQ25798: Solar panel - speed matters?

Edit: I am not using the solar panel input to power any loads, just to charge the batteries. Also, since I am using a string of panels that are on different faces (and could have different levels of sun) I am not currently uing MPPT, should I be? 

Oscope: Yellow probe is current from one panel, Blue probe is current from another panel, Pink is vbus. 

Image A: light is introduced but BQ does not start charging

Image B: light is introduced slightly faster and BQ starts charging

Hello Morgan,

Do you see any change if you enable MPPT?

Best Regards,

Christian.

MPPT box goes back to unchecked

Hello James,

Can you try setting VSYSMIN voltage to 2500mV?

Best Regards,

Christian.

Yes, it is set. What do the pull down resistors do? 

Hello Morgan,

Was VSYSMIN voltage already set to 2500mV or did you just now set this?

If you just set this value, have you tried to enable MPPT?

Do you have watchdog timer disabled?

Best Regards,

Christian.

I dont think MPPT is what we want to do. Basically I configure the chip one time and then it must work multiple days with sun coming and going. Once the sun is removed from solar panel the MPPT bit gets reset (even though the batteries are still connected and > vsysmin). Yes the watchdog is disabled.

I SAW THE 7 MINUTE TIMER! 

For this test, it did not read the panel input at first, but 7 min later it did.

BUT then I unplugged the batteries and now I can't get the test to repeat consistently. :(

How do I get VINDPM to be 6V and keep it there instead of it changing to 3.6 during HIZ?

Hello Morgan,

For testing purposes If you disable HIZ mode, do you still see the VINDPM change to 3.6V?

Best Regards,

Christian.

If I disable Hiz then it reads the solar panel input and starts charging. VINDPM changes to 6V

Is MPPT supposed to flip back to 0 when it goes to hiz? The battery voltage is 4.0 (>vysmin) but light was removed from vac2 and MPPT flipped.

Hello Morgan,

Morgan Novak said:

How do I get VINDPM to be 6V and keep it there instead of it changing to 3.6 during HIZ?

Are you able to change it after it goes in to HIZ Mode?

VINDPM register is reset to 3600mV upon adapter unplugged and it is set to the value based on the VBUS measurement when the adapter plugs in. Entering HIZ mode is causing a POR event that resets the VINDPM register, this can not be disabled.

Morgan Novak said:

Is MPPT supposed to flip back to 0 when it goes to hiz? The battery voltage is 4.0 (>vysmin) but light was removed from vac2 and MPPT flipped.

This is because of the POR event, the EN_MPPT bit will be reset to 0

Best Regards,

Christian.

That did not help me at all. What do you suggest to make the 7 min timer more reliable? 

Hello Morgan,

What is the voltage on REGN?

Best Regards,

Christian.

4.908v