BQ25504EVM-674: Using the user guide.

Hi, what's the behavior that cause you think the BQ25504 is in cold start up mode, the more detail description may help me understand what happend in your testing. And what's the 10K resistor number, R?

Hi,
I had a Vin of 1V as stated in the test prcedure and noticed that it stuck at 0.9v. The reason i believe it is in cold start up is that VSTOR is stuck at approximately 0.9V. From my understanding this is the same as in cold start up, i may be wrong though. The resistor i am speaking about is an external resistor that the technical guide for the BQ25504EVM states to install for testing. It is between STOR and GND (J6-1 and J6-3) It is for the test procedures.

Sorry for late reply, im based in the Cardiff and the weather has effected me quite severely

Thank you.

Thanks for your clarification, I noticed you said you attached a normal capacitor/supercap after the BAT pin, how about the capacitance? I guess it more seems as the power-up with battery less than UV, there has a description that - For a battery that is more than a diode drop below 1.8V, the charger may get stuck in cold startup which is less efficient and would take longer to recover.

I didn't really get a proper chance to test out a capacitor due to university closing last week due to snow. The size of capacitor is not necessarily important, it is not for much more purpose than proving and showing the charge discharge curve. I am just trying to prove that it is possible currently. any recommendations for capacity would be helpful. I understand some of the theory behind the close start up, But I am still confused on the use of the resistor between STOR and GND, what would happen to the system if a lower resistance is used, or higher. With the 10k stated the procedures did not work until this was momentarily disconnected. But I have attached a smaller resistor and it works how it should be predicted.

I intend to use a supercap after the proof that the system can work. I have been given a 0.9F 5.5v supercap, I think this is slightly overkill, but it was free so I would just like to see if I can also see the charge and discharge curves of this

Thank you

You said you attached a smaller resistor and then it works, what's the value of this resistor?

So I changed the 10k for a 1k and it would start up straight away when doing the test procedures. Im wondering if it is to do with the limited current output from a MyDAQ, what is the job of this resistor I changed to 1k?