4s3p LiFePO Battery Charging system

Seth Ammer

Other Parts Discussed in Thread: BQ24171, BQ25798, BQ24610

I am looking for some assistance in designing a battery charger for a 4s3p LiFePO4 battery pack. I have several challenges in designing the charger, mostly around the fact that I only have connection to PACK+ and PACK-. The pack has onboard protection connected to each cell according to the product datasheet, so at the very least the pack is safe. We are expecting that the battery will be topped off reguarly but will occasionally undergo a full discharge so I would like to implement a 2-stage charge profile. Does TI have a component that can support a battery pack without cell-level connection?

Thank you

over 1 year ago

0 Jeff F over 1 year ago

TI__Guru**** 167196 points

Hi Seth,

Yes. What is your input power source?

Regards,

Jeff

0 Seth Ammer over 1 year ago in reply to Jeff F

Prodigy 10 points

This application is for battery backup of normally vehicle powered devices, so a DC input of 9-16VDC. I expect I will need to boost up and then regulate down to create a stable charger supply.

0 Jeff F over 1 year ago in reply to Seth Ammer

TI__Guru**** 167196 points

Hi Seth,

If you have I2C host control, I recommend BQ25798. It is a buck-boost, 5-A NVDC charger with SYS output. V(SYS) is set a minimum system voltage and then follows the battery up to full charge. If you need a standalone (resistor controlled) charger, I only have buck chargers like BQ24171 so would need a boost converter to get the 9V input up to 15V.

Regards,

Jeff

0 Seth Ammer over 1 year ago in reply to Jeff F

Prodigy 10 points

Thank you for the suggestions, Jeff. I don't have I2C access at that section of the design yet, but it was something our team was debating. I see the BQ24171 is for 1-3 series cells; is there a 4-cell compatible alternate?

Thank you,

Seth

0 Jeff F over 1 year ago in reply to Seth Ammer

TI__Guru**** 167196 points

Hi Seth,

Unfortunately, no. You would have to move to the BQ24610 charge controller with external FETs.

Regards,

Jeff

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4s3p LiFePO Battery Charging system