BQ24770EVM-540: Can't get bq24770EVM-540 to charge or discharge my battery.

Hi Carl,

Here are a few things to check:

1) For simplicity, try testing without an e-load connected from SYS to GND. From now on, leave SYS floating instead.
2) What are your S1 switch settings? Do they match the settings given in Section 1.3 of the User's Guide?
3) Is VCELL pulled high for a 3-cell configuration?
4) What is the status of the SYSOVP bit in the ChargeOption0 register? Does this bit ever go high?
5) You mentioned in your document that VBAT measured at J3 on the BQ24770 EVM is only 0.28 V even though the actual battery voltage is 10.54 V. Have you confirmed this by measuring with a multimeter, or are you just going off of the VBAT reading in the gauge GUI?

Best regards,
Angelo

1)       I disconnected my electronic load at V_Sys.

2)       My S1 switch settings are as follows. 1: OFF, 2: OFF, 3: ON, 4: ON  (Yes, these match what is described in the EVM user's manual).

3)       Voltage at CELL (TP11) is 3.12V (high, for 3S battery configuration)

4)       SYSOVP bit is ‘0’ upon startup (default). Both “ACOK” (D5) and “BATPRES” (D3) LEDs are on.

1. After writing “810E” into the Charge Option 0 register, this bit is still 0. V_in = 19.5V, V_sys = 13.6V, V_bat = 9.1V (measured at J3).
2. When I write “3008 mA” into the Charge Current register (0BC0), V_sys and V_bat (measured at J2 and J3) go to 12.62V. Both “ACOK” (D5) and “BATPRES” (D3) LEDs are still on. However, no charging is taking place (I_bat = 0). I noticed the selections in the Charge Current pull-down menu are highlighted in yellow for some reason.

5)       The V_bat measurements have been confirmed with my Fluke hand-held DMM at J3 of the bq24770EVM-540 and at J3 & J4 of the bq40z50EVM-561. And yes, the actual battery voltage of 10.54V was confirmed with the hand-held DMM at 1N to 3P of the bq40z50EVM-561 and at the battery terminals themselves.

 

Note: the V_bat value of 0.218V happens when I write 0 mA to the Charge Current register. After this happens the “BATPRES” (D3) LED goes out and the V_sys voltage goes back up to 13.64V. Subsequent writes to the Charge Current register have no effect until I cycle V_in and restore the bq24770EVM-540 to its default state and walk through the steps again.

 

After setting the up the bq24770EVM-540 and shutting down the bqStudio program, I can then connect the bq40z50EVM-561 SMBus cable and restart bqStudio. This time the bqStudio goes right to the bq40z50-r2 gauge. The bqStudio correctly reads the battery voltage at around 10.51V (I measure 10.54V with my Fluke DMM). And the input voltage to the bq40z50EVM-561 at J3 and J4 measures 12.61V. This is the same as measured by the LabVIEW monitoring program.

 

But again, no charging is taking place. I also removed my SYSPRES jumper wire on the gauge EVM, since I disconnected the V_Sys electronic load, but it made no difference. Is it my bq40z50EVM-561 gauge module that is stopping the flow of charge current?

 Please let me know what to try next.  Thanks,

Carl Olen

Hi Carl,

I'm unable to duplicate your results on my BQ24770 EVM, which charges the battery correctly.

Let's try to get the charger side working before adding in the gauge. Try removing the gauge and directly connecting the battery pack from BAT to GND on the BQ24770 EVM. The only things connected to the EVM are now Vin = 19.5 V, the 3.3 V supply, the battery pack, and the EV2400. You can also try testing with a lower charge current setting than 3.008 A.

If you're still not having any luck after that, then instead of using the actual battery pack, you can try using an e-load in CV mode to simulate a battery and see if that makes any difference.

Best regards,
Angelo

Angelo, as always, thanks for your suggestions.

I disconnected the bq24770EVM-540 J3 from my gauge and battery line up and connected it instead to an Agilent 60501B electronic load in Constant Voltage (CV) mode. I set the voltage on the ELoad to 10V. Then, I ran my usual bq24770EVM-540 start up and initialization. This time, I set the Charge Current to 1216 mA and the Charge current flowed as expected. I then set the Charge Current to 3008 mA and the flow increased as expected. During this time, V_sys (J2) was left floating. V_sys and V_bat measure 9.7V on my monitoring program when I_charge is 1216 mA; V_bat goes to10.1V when I_charge is set to 3008 mA. I can set the Charge Current freely and change the value as expected. But when I set it to zero, the BATPRES LED (D3) goes out and I can no longer set the Charge Current to a non-zero value via bqStudio.  I think this is all as expected.

So, it looks like everything with my bq24770EVM-540 is working as it should. I believe it is the bq40z50EVM-561 & battery that is blocking the charging function in my original setup.

What steps do I need to take with my bq40z50EVM-561 to allow it to accept a charge current into my battery line up?  Please let me know.

Best regards,

Carl Olen

Hi Carl,

Thanks for the update! That's great news.

Would you mind creating a new E2E thread with the BQ40z50 in the title? That way, someone from the gauge team will be able to see your thread and provide suggestions.

Best regards,
Angelo