BQ78PL116 & BQ76PL102 with LiFePO4 and generally

Hello Ran,

I am checking the possibility of using BQ78PL116 & BQ76PL102 with LiFePO4 8S1P pack.

We are using BQ78pl114 with LiFePO4 (PHET 18650) chem 405

1)as I understand BQ78PL116 has a gas gauge embedded and the software that we are using is BQwizard.

      does BQwizard has a chemistry learning cycles (like BQeasy...)?

Read sluu556 to understand final gauging will work when you will have generate and load the .aux file in the BQ

2)is there a way to set the under voltage protection value? I think now it is set on 2.5V, which is a bit (just a bit though) high.

NO! tha is the limit with LiFePO4 it is a serious problem if you will have to draw hight current .....

3)in your experience, does the chip needs a cooling system, having transfering 1A sometimes through him for balancing?

NO copper pad is OK

4)in the application note I saw a thermistor for every cell, is it possible to connect only part of them? and if so, what should I connect instead?

No, editing the Tmap file will alow you to do what you want

Regards

Robert

Thanks for the reply.

so, for summation,

what are the problems you see when using these king of chip (bq78pl11*) with LiFePO4 and high currents?

would you recommend us to continue with the development with this chip?

thanks

As BQ have 2.5V min good working voltage, you should test your LiFePO4 pack and check that voltage on cell1 (the one that power the BQ) will never drop below 2.5V during the load pulse.

Specialy when pack is close to be discharged

In fact BMS wil be reset as soon as voltage on cell 1 will drop (even few ms) below 2.5V

MAY BE SOME PEOPLE FROM TI SHOULD CONFIRM  !!!

Rgds    Robert

thank you very much

you have been very helpful

I confirm, I've had it happen on me.

HI, Robert,

We are using bq78PL116EVM with LiFePO4, just like you.

It's a 2.1V~3.65V battery,but the operating voltage range of bq78PL116 is 2.8V to 4.5V.

I am going to do the Data Collection Procedure for generating .AUX file, and it need to completely discharge.

I can use Adders to make the battery voltages in the operating range,but it means that the .AUX file is not correct.

So I wonder that how did you solve the problem.

Thanks!

Regards

Fred

Hi Robert,

actually the chip is still fully operating even at 2050 mV which is my Cell under Voltage (despite what is written on the datasheet.

this was tested with 4 different chips with several 10S and 8S packs.

the only problem I encountered is that the recovery voltage for extreme under voltage is 2900 mV and the datasheet said it has to stay that way which means that precharge will take much longer.

I don't see how that is a problem for the AUX file creation, if the communication is working and the ADCs are working then the AUX file should work fine in my opinion.

I haven't encountered any problem, and I'm working with this chip since January and produced number of PCBs with it.

hope I helped...

Hi Aloni,

thanks for your reply!

now I use the cell simulator to simulate 2.1~2.5V/cell with 4S1P.

but when I'm going to open bqWizard, there's a warning:

"Unable to connect to device. Please check power and the connections to the hardware."

and both the pin VLDO1 and VLDO2 of bq78PL116 are  wrong voltages.

it means that the power is not correct, right?

so if I want to go data collection procedure, it has to be full dischage.

it means the real battery should be down to its cut of voltage, 2.1V.

according to my cell simulation result, the IC would work Incorrectly.

or any parameters should be modify to avoid the situation? such as PUV, CUV....

Could you provide the details for me to generate the aux file?(I have reviewed "Chemistry Selection for bq78PL114" already, all I need is how to set the parameters or do anything to make the EVM work correctly even if the battery voltage is down to 2.1V/cell, or even do nothing.)

And I have no idea how to test the ADCs  working find or not.

thank you!

Fred

Hello Mr. Chang,

7823.BQ_details.zip

I attached my parameters and AUX file.

you can view them via excel.

if you want to be sure you can set your CUV to about 2.4 volt - you won't loose a lot of capacity there.

less than a minute of work and you can be sure everything will work, in a 10Ah and more rezolution it is not that much.

best regards

Hello Fred

     I came across the same problem as yours.I am a aftersale technicain.I receiced a battery pack (10s1p) with the protection board of bq78PL116.I replaced the new bq78PL116 ic for such a protection board.When I open bqWizard software to build the communication between computer and bq78PL116 protection board.It display a warning message:

    "unable to connect to the device . Please check power and the connections to the hardware "

    I have check the connection about communication,it is correct.I thought that the V1 and V2 is the power for bq78PL116,is it right?Have you solved such a problem about connection to device?Would you like to help me to solve it?

   When I connect to the good protection board to computer using the same tool.it is correctly connected.

   Thank you.

    Shao