Charging depleted batteries BQ77910A

Tomasz Olczak

Other Parts Discussed in Thread: BQ77910A

Can't find the information if BQ77910A is protecting against charging low voltage batteries?

Can anyone help?

If this function is not implemented is it true that low voltage cell will be detected as an open cell (voltage less than 1V) and charging won't be possible?

Tomasz

over 12 years ago

0 Ulrich Steiner over 12 years ago

Prodigy 70 points

Hi Thomas,

the BQ77910 has got a programmable under voltage (UV) comparator. Depends on the implemented parameters when a total shut down is performed.

0 Tomasz Olczak over 12 years ago in reply to Ulrich Steiner

Prodigy 50 points

Thanks Ulrich,

I know that there is a UV comparator but it won't prevent from charging the pack if charger is connected (through body diode of discharge Mosfet).

During UV only discharge FET is opened, charge FET will be enabled immediately after charger detected.

Tomasz

0 Ulrich Steiner over 12 years ago in reply to Tomasz Olczak

Prodigy 70 points

Hi Thomasz,

low current charging at low cell voltage is job of the charger.

BR

0 Tomasz Olczak over 12 years ago in reply to Ulrich Steiner

Prodigy 50 points

Can't fully agree with your statement.

Charging low voltage cells could be very dangerous and it is recommended not to do that.

The charger takes the responsibility only on the pack voltage level.

What if only one cell is shorted?

Tomasz

0 Ulrich Steiner over 12 years ago in reply to Tomasz Olczak

Prodigy 70 points

Think we talk about LION cells. The job of the protection curcuit is to avoid low voltage cells. Most of the LION charger have the so called refresh mode until the voltage is in a range for full charge. There is no danger as long this process is temperature controlled.

A short LION cell is lost and can be charged with any current, it will stay short. The protection circuit will shut down this package.

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Charging depleted batteries BQ77910A