bq20z65 cell balancing

Ronaldo Poltronieri

Other Parts Discussed in Thread: BQ2040, BQ20Z65

Dear Sir,

I am developing a battery pack - Li Ion 14V8 8800 mAh - which uses a bq20z65 gas gauge ic. Actually, I am updating the product from the bq2040.

I understand the cell balancing function can extend the battery life.

Is it possible to predict how much the battery cycle life will extend? 5%, 10%, x%?

Thanks

Ronaldo

over 10 years ago

0 Onyx Ahiakwo over 10 years ago

TI__Guru* 76230 points

Hi Ronaldo,

It is not possible to make such predictions as this is chemistry dependent. However , numerous tests has been carried out that shows incoporating CB actually does extend battery life.

-Onyx

0 Alexandre Cherpillod over 9 years ago in reply to Onyx Ahiakwo

Intellectual 425 points

Hi Onyx,

I'm actually using the bq20z65 with a 3S pack made of 7.7Ah cells.
I want to use instead a 3S3P pack made of smaller capacity cells (7.7/3 Ah each)

Is that applicable ? Do you think the balancing will be good and fast enough ?

Thanks,
Alex

0 Onyx Ahiakwo over 9 years ago in reply to Alexandre Cherpillod

TI__Guru* 76230 points

Hi Alex,

I will suggest using external fets to increase the cell balancing current as per the app note attached since you will have 9Ah total given you have 3p configuration.

thanks

Onyx

7485.slua420a[1]_fast cell balancing using external mosfer.pdf

0 Alexandre Cherpillod over 9 years ago in reply to Onyx Ahiakwo

Intellectual 425 points

Hi Onyx,

Thanks for your answer, but in fact each battery of the 3S3P will be 7.7/3 = 2.56Ah each. The total is 7.7Ah (not 9Ah)
Actually I'm using 7.7Ah but in 3S only and without using external fets and the time of balancing is totally right. So if I use the same total capacity but in 3S3P instead of 3S is it going to lead to a longer balancing ? I don't think so ?

Thanks,

Alex

0 Onyx Ahiakwo over 9 years ago in reply to Alexandre Cherpillod

TI__Guru* 76230 points

Hi Alex,

Thanks for the clarification, i had misunderstood your text thinking you meant each had 3mAh capacity.The bq20z65 carries out balancing based on state of charge and not voltage, so I will recommend basing your descision to use external fets or not by carrying out similar calculations in the app note.

thanks

Onyx

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bq20z65 cell balancing