BQ28Z610: Cell Balancing Time

Fred Arnold

Part Number: BQ28Z610

Hi,

I am wondering if the calculation below to calculate the Balance Time is correct.

If I use the Resistors on the Eval Board (100R and 105R) the I get a Balance time of approx. 16000 s/mAh per cell. This is assuming a duty cycle of 66% but there is nothing mentioned where this value comes from.
Please confirm that this is correct. if so, is there a way to speed the process up?

Thanks,

Fred

over 6 years ago

0 Batt over 6 years ago

TI__Mastermind 42535 points

I'll have to look into it. I suspect there's an error with the equations. I'll confirm shortly.

0 Batt over 6 years ago in reply to Batt

TI__Mastermind 42535 points

Those equations are correct. At 105, 100Ohm the balancing time comes out to 133seconds/mAh.

= (3600/(3.7/(100+105)))*(DUTY/1000). = 131.6s/mAh.

0 Fred Arnold over 6 years ago in reply to Batt

Intellectual 680 points

Hi Batt,

Thanks for the confirmation.

Checking your equation, I assume the DUTY must be 0.66 and not 66.
One of the resistor values should be also the FET resistor which is apparently 150 Ohm.

Please confirm that the following equations are correct:

Bal Time/mAh Cell 1 = (3600mAs / (3.7V / (150Rfet + 100Rvc1))) * (0.66 / 1000) = 161s/mAh.
Bal Time/mAh Cell 2 = (3600mAs / (3.7V / (150Rfet + 100Rvc1 + 5Rvc2))) * (0.66 / 1000) = 164s/mAh.

Thanks,
Fred

0 Batt over 6 years ago in reply to Fred Arnold

TI__Mastermind 42535 points

Yeah, that's right.

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BQ28Z610: Cell Balancing Time