BQ25750EVM: BQ25750EVM

Hello Jimmy,

Thanks for working with us on this. I've got a few questions to help us debug.

What's your battery and input voltage?

What's your charge current set at and what is your test setup?

What register settings are you using?

Best Regards,
Ethan Galloway

Hi Ethan,

We use LiFePO4 24V 24Ah battery. The VAC input voltage is 28V and charge current at 5A.

We bought BQ25750 EVM board and EV2400 board. We follow the EVM user's Guide to perform the test.

Now the battery charge is successful. But we have trouble in reverse mode.

We would like to have the charged battery as power supply and regulates 24V battery voltage to 28V SYS terminal voltage after 28V VAC input is removed. The discharge current could be 15A.

Could you provide us a register setup file to implement the test scheme as described above?

Thanks,

Jimmy

Hello Jimmy,

For your condition, I think the auto reverse mode on the BQ25750 will work well. You can check this FAQ page for a summary of reverse mode

I recommend the following register settings for this test condition:

Watchdog = Disabled
VSYS_REV=28000mV
EN_AUTO_REV=1
All other registers are default

With auto reverse mode, reverse mode will activate once VAC drops below the ACUV threshold and supply 28V to the system.

Let me know if you have any questions about this and let me know if you are still having trouble with this.

Best Regards,
Ethan Galloway

Hi Ethan -- We tried what you suggested for those registers settings, but not work.

Basically, we use bqStudio GUI to setup 28000mV, the register 0x0C reads back value is 0x15E0, and SYS_LOAD voltage is 25.4V (charged battery voltage value), not the expected reverse voltage value 28V after VAC_in is removed. 

* Created: Mon Sep 16 09:33:38 PDT 2024
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* BQZ Container: Charger_2_00-bq25750.bqz
*
Charge Voltage Limit	00	10
Charge Current Limit	02	190
Input Current DPM Limit	06	640
Input Voltage DPM Limit	08	348
Reverse Mode Input Current Limit	0A	1E0
Reverse Mode System Voltage Limit	0C	15E0
Precharge Current Limit	10	140
Termination Current Limit	12	A0
Precharge and Termination Control	14	0F
Timer Control	15	0D
Charger Control	17	C9
Pin Control	18	C0
Power Path and Reverse Mode Control	19	23
MPPT Control	1A	20
TS Charging Threshold Control	1B	96
TS Charging Region Behavior Control	1C	57
TS Reverse Mode Threshold Control	1D	40
Reverse Undervoltage Control	1E	20
VAC Max Power Point Detected	1F	00
Charger Status 1	21	0C
Charger Status 2	22	80
Charger Status 3	23	02
Fault Status	24	00
Charger Flag 1	25	01
Charger Flag 2	26	00
Fault Flag	27	00
Charger Mask 1	28	00
Charger Mask 2	29	00
Fault Mask	2A	00
ADC Control	2B	60
ADC Channel Control	2C	02
IAC ADC - Use Field View	2D	00
IBAT ADC - Use Field View	2F	00
VAC ADC	31	00
VBAT ADC	33	00
VSYS ADC	35	00
TS ADC	37	00
VFB ADC	39	00
Gate Driver Strength Control	3B	00
Gate Driver Dead Time Control	3C	00
Part Information	3D	02
GM Adjust	61	30
Reverse Mode Battery Discharge Current	62	02

Above is the setting register value file. Could you help to check what is wrong in our setting? Or could we have an online meeting so yo can directly instruct us what we should do?

Thanks,

Jimmy

Hello Jimmy,

Thanks for being patient with this. We'll get back to you later this week.

Best Regards,
Ethan Galloway

Hello Jimmy,

Ethan is out of office, so I will be taking over this question.

I have a few question:

Do you have a system load, or are you just measuring the voltage at the terminal?

Can you enable the ADC, and provide the register information again?

In the register logs that you sent, the battery is in taper mode, and Reverse mode is off. Can you confirm the adpater is not present? I'm not sure why it would be in taper mode if adapter is not present.

Best Regards,

Christian

Hi Christian -- Thanks for stepping in to help. I am out of office for the rest of week and will provide information to you next Monday.

Jimmy

Hi Jimmy,

Let us know if there is any update here.