BQ25792EVM: Testing Procedure for 4S configured BQ25792EVM

Hi Jeff,

 Thanks for response.

Q1) will i get 12v output at Vsys when i applied 5V,3A at Vbus and 5V,3A at Vbat?

i have applied the same but i got only 5V at Vsys.

i have followed the connections provided by the document.in table 1-3.

initially through I2C i am disabling the watchdog, TS , and enabling the ADC.

I have read all the registers found that it was going into HIZ mode.(Charger control register 0 = 0xa6) when i connected power to ILIM_HIZ pin resistor divider network.

but i have observed that charger status register is 0x0D. means good source.

input for ILIM_HIZ is 1.24v means around 300ma but when i am reading the register through i2c its value is 1230ma.

Q2) is there any document to test the charger in 4S mode?

Q3) is this IC worked for 4S configuration? is there any one successfully worked this IC in 4S mode.

Q4) what happen when i am given 12V and 8A supply at VAC1 and connected the battery with with voltage of 14v and enable the charging, will this battery charges? is this BAT current 2A or not?

Q5) what is the time you will available according to ISD to answer my questions? I have lots of doubts regarding this Charger in 4S mode.

Best Regards,

Malesh Nakka

Hi Jeff,

  Thanks for your response.

           I have made the connections as you mention in the document BQ25792EVM. PROG pin is connected with 27k ohm resistor. so it was works in 4S mode with 750Khz(switching frequency). i have connected the power supply at VAC1 , which is 15V(0-110V), 0-8A (set the power supply at maximum current limit(8A)). ILIM_HIZ is connected to 3.34V through resistor divider network, that leads to Input Limit Current to around 3A. I have enabled the charging results is STAT LED is ON. after that i have connected the 14.4V battery through a ammeter. if the battery voltage is 14.4V that means it should charge in FAST CHARGING MODE that means with 2A current. BUT it was not charging with 2A current. It was charging with around 1A. why this was happened?

from the data sheet of BQ25792, after the Battery reaches 12V, it should went to Fast charging mode means it should charge the battery with 2A current. But WHY this was not happening?

MY max input power to the IC at VAC1---------15*8A=120W

Maximum power the IC can take------------------15*3A(ILIM_HIZ=3.34)=45W

needed power for BATTERY to charge the battery with 2A at 14.4V--------------14.4*2=28.8W only

BUT why the IC was not charging the battery with 2A?.

NOTE:

Converter is also working. (observed the triagular wavewith frequency 21.4khz at SW1 and SW2).

AT Power ON  i am disabling Watch DOG, TS and ENABLING the ADC.

Thermister was removed , which leads to TS=85% of Vregd means NORMAL MODE.

Best Regards,

Malesh Nakka

Malesh,

Is the /CE pin pulled low by shunt on JP17?  Is the CE bit in REG0Fb5 set?  

BTW, if TS is disabled in I2C register, then voltage on TS is irrelevant. 

What do the status and fault registers report?

Regards,

Jeff 

Hi jeff,

      Thanks for response.

CE pin is connected to ground and CE bit at REG0F is set.

status registers:

charger control register0  ----------- 0x0D

charger control register1  ----------- 0x70

charger control register2  ----------- 0x01

charger control register3  ----------- 0xC0

charger control register4  ----------- 0x00

fault status register0-------------------0x00

fault status register1-------------------0x00

There are no faults are present. Please suggest me why the charging current was not constant in FAST CHARGING mode?

Q1)can we control the charging voltage and current through I2C communication? if YES , suggest me the process.

Best Regards,

Malesh Nakka

HI Malesh, 

I need to see the registers 0x1B to 0x27 to show the status and fault registers.

For changing the voltage and current, first ensure that REG0Ab6:7 = 11 for 4S.  If so, then you can change charge voltage in REG0x01-0x02 and charge current in REG0x03 to REG0x04.

Regards,

Jeff

Hi Jeff,

         They are Status registers not control registers (sorry for the mistake).

Best Regards,

Malesh Nakka

Hi Michael,

                 I have changed the current and voltage registers that was suggested by the Jeff, I had set the current to 200mA and voltage to 15000mV but the charger doesn't care about the settings. It changes charging status to Termination . but the charging never stops and the current never controlled .

If i increasing the input voltage(by manual source), input current and charging current also increasing , it was like a battery is connected parallel to the power source. Vbat is approximately equal to the input voltage. i didn't seen any controlling  from the charger IC. and input current and charging current also approximately equal.

but the there is a wave at SW1/SW2 means internal converter working. but i didn't seen any controlling as of now.

please share if there any video of your testing of the IC with 4S configuration to understand in better way.

if you have any other information about this charger please share to me.

I am gladly waiting for your answer.

Thanks& Regards

Malesh Nakka