bq76PL455A-Q1: bq76PL455A-Q1

Actually if I choose a shunt resistor around 3 Ω,then it should have 5w power. I have doubt in if the bq76PL455A-Q1 can support this value for resisitor as a thermal heat limitation?
Kind Regards
Elham

Hi Etham,

In addition  to what Roger has  suggested, you must also consider the offsets  that will be measured when balancing. 1.35A is  very high for balance current, although technically possible. As Roger suggested, it will  get very hot, so don't be surprised if you  put the pl455 into thermal  shutdown while  balancing. 

 Hi David,

Actually I will try to control the balancing rate by using PWM signal for switching.I mean 1.35 A is the maximum rate while charging .and by getting the feedback from temperature sensors that I use on top of each cell near the resistor, I will try to control temperature at the same time.So, you mean the thermal shut down will automaticlly shut down the device?If yes that would be a problem for not letting it use such a current for balancing.

Elham,

You are correct. The heat generated by the power dissipation in the FETs/resistors can cause the part to automatically go into shutdown, since that is considered the "safe state", assuming the MCU will detect this and disconnect the pack.

As long as you can manage the thermal, it is technically possible. As Roger said, ~200mA is a popular passive balance current. Much higher than 1A is when active balancing becomes more necessary.

our current BMS is doing the passive balancing with max 1.35 A current and is working well.That's why I am trying to do as well with this current.I am now on the midle of ordering,so do you think Is it possible to diactive the thermal shut down?Or if I just control the thermal heat by chnaging the duty cycle switvhing signal I can overcome it before getting shutdown many times?

Elham,

The thermal shutdown (TSD) cannot be deactivated, as that would be a major safety concern. It will be necessary to manage the thermal performance for the system,

but I am wondering if I would face multiple shut down in my design .Do you have any suggestion for this problem?

Dear Dave,
Thank you for all your good information.As I understood,i will try to manage switching and duty cycle by software to control the PCB thermal before getting the thermal shut down level.
Kind Regards
Elham

Dear Dave,
I was thinking about how to overcome this problem.The idea is to do balancing periodically through command from MCU so that the system would not face a high balancing current.Do you think this will oevrcome it?