BQ24450: Single Cell Lead Acid Battery Charger

RAJAN KS

Part Number: BQ24450
Other Parts Discussed in Thread: BQ24610, BQ24650

Dear sir,

Greetings...

We are in the process of developing a single cell Lead Acid Battery Charger as one of our regular product. We have selected your BQ24450 device as charge controller for this application. We have tried calculating the Resistor values (RA, RB, RC and RD) for 6V Battery (3 Cell Lead Acid Battery) as per the page No.14 of BQ24450 data sheet and found the Resistor values calculated are matching as per the page numbers 14 and 15 of your data sheet.

But when we tried calculating the resistor values for 2.1V Battery (Single Cell Lead Acid Battery), the value of RD is coming as negative value. Can you please support us by providing the calculations for all the Resistor (RA, RB, RC and RD) values, considering Single Cell Lead Acid Battery (2.1V)?

Thanks

With warm regards,

K.S.RAJAN

Chief Executive

Embit Technologies, Bengaluru India

Email : embit.tech@gmail.com

over 3 years ago

0 Nick Brylski over 3 years ago

TI__Mastermind 19195 points

Hello Rajan,

I'm taking a look into your question, may I know the charging current you are targeting?

Thanks,

Nick

0 RAJAN KS over 3 years ago in reply to Nick Brylski

Prodigy 40 points

Dear Nick Brylski,

Greetings...

Thanks for your kind support.

We are targeting 3 Amps charging current.

Thanks

with regards,

Rajan KS

0 Nick Brylski over 3 years ago in reply to RAJAN KS

TI__Mastermind 19195 points

Hello Rajan,

Would not recommend this part for 3A charging. It is a linear charger and the heat rise would be substantial.

Please consider BQ24610 or BQ24650: www.tij.co.jp/.../slua992.pdf

Best regards,

Nick

0 RAJAN KS over 3 years ago in reply to Nick Brylski

Prodigy 40 points

Dear Nick Brylski,

Greetings...

Thanks for your kind reply.

We have already manufactured the PCB with BQ24450 and for our current requirement we want to go ahead with BQ24450. However, for our new designs, we will use the part that you have suggested us ( BQ24610 or BQ24650).

Meanwhile, Can you please support us by providing the calculations for all the Resistor (RA, RB, RC and RD) values for BQ24450, considering Single Cell Lead Acid Battery (2.1V)?

Thanks

with best regards,

Rajan KS

0 Nick Brylski over 3 years ago in reply to RAJAN KS

TI__Mastermind 19195 points

Hello Rajan,

A negative Rd value is equivalent to STAT1 sourcing current but this is not possible with the device (STAT1 can only sink). For BQ24450 you must charge the lead acid battery greater than the Vref of 2.3V.

Best regards,

Nick

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BQ24450: Single Cell Lead Acid Battery Charger