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BQ24650 Battery Charger for LiFePO4 -Automotive Grade version and Cell Balancing

Vijay DALMET
Prodigy 140 points
Other Parts Discussed in Thread: BQ24630, BQ24650
Hi,

I was looking for Automotive grade battery charging IC for 4 LiFePO4 Cells in series. Coulden't find one on TI. 
At this time I have some questions about the one closest I found i.e. BQ24650:
1. BQ24650 datasheet doesn't specify any automotive qualification, yet the application mentions 12 to 24 Volt Automotive Application. 
If this IC is not automotive qualified, is it reliable to use in automotive application?

2. Is there any LiFePO4 charing IC with automotive grade 1 or 2, capable of charging 4 cells in series? 3. 
The charging application is for multiple cells in series. 
However, LiFePO4 cells need balanced charge on each cell in series else one or more cells may be overcharged. 
Does this IC not care about balanced charge? Is the cell balancing during charging expected to be handled seperately? Would appreciate if someone can help clarify this.

Thanks.

Vijay
  • 0
    TI__Genius 11480 points
    Vijay,

    In terms of automotive - does it have to be automotive qual (Q marked?), or is it a "nice to have"? I know in some applications like infotainment or other non-critical systems, it does not need to be automotive qualified.

    However, I would recommend you look at the bq24630. This part is in the same family as the bq24650, but optimized for LiFePO4. While not automotive qualified, it is tested from -40C to 155C, making it possible to use in these non-critical systems.

    Unfortunately, I don't believe we have any automotive qualified parts yet. They are coming, though, I believe!

    In terms of cell balancing, that is done externally. I am not familiar with the product families, but we do offer AFE's and Gauges that will do cell balancing.
  • 0 in reply to David Wiest Jr
    Prodigy 140 points
    Hi David,

    Thanks for quick reply. Automotive grade is nice to have for our application as it is non-critical system but the application would be under the hood of a car and hence high operating temperature is critical requirement. I had gone thru bq24630 specifications earlier (in fact searched for all LiFePO4 charger ICs), but it also specifies 85C as max operating temperature. Are you suggesting that though the datasheet specifies 85C, testing on this device suggests this can withstand 155C?

    Thanks for clarifying cell balancing question. We will incorporate that in our design distinctly.

    Regards,

    Vijay
  • 0 in reply to Vijay DALMET
    TI__Genius 11480 points

    Vijay,

    Thanks for the clarification. Unfortunately,  I don't think we have any chargers that fit the bill for LiFePO4 and Q (automotive) grade. However, in the datasheet it specifies an absolute max temp (without damaging the IC) from -40 C to 155 C.

    The recommended operating temp is 0C to 125C, so we do test over a larger temperature range to work with automotive, but do not run through the required automotive qualification testing.

    One thing to note is that there is a thermal shutdown feature integrated into the charger IC. At 145 C, the device will shut down to prevent damage to itself. This is a feature you will see on almost any battery charger, though.

  • 0 in reply to David Wiest Jr
    Prodigy 140 points
    Thanks David for the clarification. We will go ahead with bq24630 now.