BQ24296: Problems with depleted battery charging

Egor Markov

Part Number: BQ24296

I have a battery with internal overdischarge protection circuit, which disconnects battery, when voltage on cell below 2.4V.

When I try to charge it with BQ24296, i have input current into battery 1uA only, but by specs it must be 100mA (DS 9.3.3.2 figure 16). Why it happens?

Registers:

0x34

0x1b

0x40

0x10

0xb2

0x8c

0x7f

0x0b

0x95

0x00

over 5 years ago

0 Egor Markov over 5 years ago

Prodigy 180 points

Does anyone know the cause of this problem?

0 Ning T over 5 years ago in reply to Egor Markov

TI__Mastermind 46551 points

Hi,

What is the VBAT pin voltage of the BQ24296?

Thanks,

Ning.

0 Egor Markov over 5 years ago in reply to Ning T

Prodigy 180 points

Hi Ning,

In general conditions 0.3-0.6V. When all load disconnected (MCU and sensors) and BQ24296 in standalone mode - 1.3V.

Also, when battery depleted and power supply connected, VSYS voltage is lower, than defined by registers. For example: if I set REG1[1:3] to VSYSmin 3.3V, on the output will be 2.5-2.7V

0 Egor Markov over 5 years ago in reply to Egor Markov

Prodigy 180 points

Any ideas?

0 Ning T over 5 years ago in reply to Egor Markov

TI__Mastermind 46551 points

Hi,

The VBAT pin of the BQ24296 should see the actual battery terminal voltage when the battery is present. Please double-check the battery connections and check if the battery internal overdischarge protection circuit prevents the battery from being charged.

Thanks,

Ning.

0 Egor Markov over 5 years ago in reply to Ning T

Prodigy 180 points

Yes, battery is connected. I have around ten devices with this problem. Battery overdischarge protection circuit works well, and close FETs between battery + terminal and pack + wire. At this conditions VBAT see around 0.4-0.6V, and I have input current from VBAT around 1uA

0 Egor Markov over 5 years ago in reply to Egor Markov

Prodigy 180 points

I mean internal battery overdischarge protection circuit. Cutoff voltage is around 2.4V

0 Egor Markov over 4 years ago in reply to Egor Markov

Prodigy 180 points

Unfortunatelly, TI don't answer to this issue and all similar. But i found simply solution. Just connect VSYS to VBAT via ~100 Ohm resistor (to limit input current) and Shottky diode (I use MBR0520).

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BQ24296: Problems with depleted battery charging