BQ76925: What happens if a battery with only one or two cells is attached and should be monitored?

Christoph Redecker

Part Number: BQ76925
Other Parts Discussed in Thread: BQ25713, BQ78Z100, BQ4050, BQ28Z610

Hello,

as per the datasheet, the BQ76925 supports 3 to 6 Li-based cells.

To me it's unclear though if it might be a problem if a pack with only one or two cells (1S or 2S) is connected. I'd still like to be able to measure cell voltages and, for a 2S pack, to balance them.

- Would the BQ76925 support this?

- If so, are there any caveats?

Thanks for helping!

over 5 years ago

0 WM5295 over 5 years ago

TI__Guru 54715 points

Hi Christoph,
The bq76925 is not intended to monitor less than 3 cells. One issue is the supply voltage drop as the cell voltage changes, another could be uncertainty of the operation of the amplifers with low bias voltages. Operation with 2 cells is not recommended.

0 Christoph Redecker over 5 years ago in reply to WM5295

Prodigy 20 points

Now that you mention the potentially too low supply voltage it dawns on me that this is the wrong part altogether. It has no separate supply input, so I can't power it from an independent source.

I'm actually looking for a companion to the BQ25713 (or similar from that family) in a battery charger. It should at least provide cell voltage sensing (analog mux + level shifting + ADC) and a way to balance the cells. Can you recommend one?

0 WM5295 over 5 years ago in reply to Christoph Redecker

TI__Guru 54715 points

Hi Christoph,
2 cell monitor functions with balancing have gauges in our products. Depending on your desired interface you might look at BQ78z100, BQ28z610, BQ4050, or other options at www.ti.com/.../overview.html

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BQ76925: What happens if a battery with only one or two cells is attached and should be monitored?