BQ25756: Operation with System Load but no battery

Harry Courtice

Part Number: BQ25756
Other Parts Discussed in Thread: BQ25750, BQ25751

Tool/software:

Hi,

This question is similar to "e2e.ti.com/.../bq25756-driving-the-system-when-the-battery-is-absent", I don't see an answer to that question, so I am asking here.

We plan to use this part in our product both with and without external 13.8Lead-Acid or LiFePO4 battery. The battery will be optional depending on the user's application. Our product can draw peak current to up to 3.5A, and may draw as low as 100mA during start-up. Typical current draw is 300mA at 13.8V.

Is this part suitable for operation without any battery? Our requirement would be that the converter supplies 13.8V with current varying between 100mA and 3.5A with no battery attached.

Thanks,

11 months ago

0 Ethan Galloway 11 months ago

TI__Mastermind 31350 points

Hello Harry,

I'll get back to you later this week on this.

Best Regards,
Ethan Galloway

+1 Ethan Galloway 11 months ago in reply to Ethan Galloway

TI__Mastermind 31350 points

Hello Harry,

I think the BQ25756 will work for you here if there's an MCU in the circuit. When the LiFePO4 or Lead-Acid battery is absent, you'll need to disable precharge and termination. The registers would be EN_PRECHGE=0 and EN_TERM=0. A load that varies between 100mA or 3.5A should be fine for the charge current is greater than 3.5A.

Also, we have a dedicated lead acid battery charger that is coming out by the end of the year. It will be similar to the BQ25750.

Let me know if you have any questions about this.

Best Regards,
Ethan Galloway

0 Harry Courtice 11 months ago in reply to Ethan Galloway

Prodigy 20 points

Hi Ethan,

We will have a microprocessor connected to the I2C lines, so we can do this setup once the controller has booted.

What is the part number of the upcoming Lead-Acid specific part you mentioned?

Regards,

Harry.

0 Ethan Galloway 11 months ago in reply to Harry Courtice

TI__Mastermind 31350 points

Hello Harry,

The part is called the BQ25751.

Best Regards,
Ethan Galloway

Power management

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BQ25756: Operation with System Load but no battery