BQ79612-Q1: One single balancing resistor instead of 2

Hi Abbas,

Are you referring to our 2 Rcb resistors in parallel in our EVM schematic? If this is the case, keep in mind that the parallel resistors bring Rcb to 5 ohms. Replacing both resistors with a single 20 ohm resistor brings significantly increases Rcb.

In order to calculate the cell balancing resistance, you need to do:

Rcb_total = 2(Rcb) + Rcbfet

Where Rcbfet is 1.5 ohms.

With this you can calculate your cell balancing current with V = IR, where V is your cell voltage and R is the Rcb_total you just calculated.

With a larger Rcb, you will have lower cell balancing current. But yes, this is okay if it is the goal.

Best,

Zachary

Hi Zachary,

No it's not what I meant.

Let me say it differently: if I remove one of the two Rcb I understand that the current will increase for sure but would the balancing still work with only one Rcb ? Would this not disturb the biasing of the internal Mosfet QCB?

Rcb_total remains at the same value but I increase one Rcb and remove the other one: Rcb_total = 2(Rcb_a) + Rcbfet= Rcb_b + Rcbfet

In other words, on the PCB I use one resistor instead of 2 but keep same Rcb_total.

BR, Abbas

Hi Abbas,

Could you kindly provide a diagram or simple drawing for which resistors you are planning on removing and which resistors you would like the change?

Best,

Zachary

Hi Abbas, 

Yes, it is totally fine to replace the CB resistors, this won't effect the MOSFTS. Although from what I understand you are increasing the resistance from 10 ohms to 20 ohms, this won't keep the CB current the same.

Best,

Zachary