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Original question:

BQ24640: Can BQ24640 charge lead-acid battery?

BQ24600: Lead-Acid application

Delaney Berger
Intellectual 2475 points
Part Number: BQ24600
Other Parts Discussed in Thread: BQ24610

Hi Team, 

Customer is using BQ24600 on their board for charging a Li-ion battery. They changed the battery chemistry to a lead acid battery. They're in the layout phase and don't wish to make changes to the schematic and look for new parts. Also, would like to hold the IC in case we go back to Li-ion.

Can the BQ24600 be used to charge a lead-acid battery, or would they need to use the BQ24610? 

I found TI document SLUA992, which talks about modifying circuits around Li-ion charger IC to be compatible with lead acid battery. Their application is a backup application as per section 2.2.

Based on my understanding, they should not do any changes to the BQ24600 and be able to use it because the charging profile for backup application in SLUA992 Figure 3 is same as the charging profile in Figure 5 of BQ24600 datasheet. Or would there need to be modifications to the circuitry? Could you please advise?


Thank you, 
Delaney

  • 0
    TI__Mastermind 24075 points

    Hi Delaney,

       Lead acid charging requires a float charge, during which we maintain a lower charge regulation voltage to prolong the lead acid battery life.

    Repeating Applications: On BQ24610 we do this with the STAT2 pin which solely indicates whether charge is complete or not. On BQ24600 however, we only have a generic STAT pin for reporting on all faults and charge in progress, so you wouldn't be able to implement this on BQ24600 through hardware only implementation.

    Backup Mode: Yes, you should be able to set the charge regulation voltage to the float regulation value through just sizing the resistor feedback network. The downside with BQ24600 vs BQ24610 is that BQ24600 has a non configurable hard 5 hour safety timer, after which the charger will be disabled. This is programmable on BQ24610 and can be disabled. I would recommend BQ24610 in both cases, as this functionality is based off of pulling TTC pin of BQ24610 low to disable termination and safety timer.

  • +1 in reply to Kedar Manishankar
    TI__Intellectual 2475 points

    Thank you Kedar, 

    I will mention that the BQ24610 is preferred. 

    However, since the customer would prefer to not make any modifications to the schematic, it looks like the BQ24600 should work with just resizing resistor feedback network, correct? 

    Thank you, 
    Delaney

  • 0 in reply to Delaney Berger
    TI__Mastermind 24075 points

    Hi Delaney,

       The downside to the specified backup application is the longer charge time required, as we want to disable termination and keep the charger maintaining the float charge regulation voltage. You don't have that luxury on BQ24600 as the safety timer and the termination can't be disabled, like it can on BQ24610. For BQ24600, charge is disabled automatically after 5 hours. In that situation you are relying on lead acid self discharge to kick you back into a new charge cycle, which defeats the purpose and would reduce battery longevity. They would need to have some external implementation to restart charge cycle after 5 hour safety timer is triggered. I think it is easier to use the BQ24610

  • 0 in reply to Kedar Manishankar
    TI__Intellectual 2475 points

    I see, thank you Kedar! 

    I think customer will go with BQ24610!

    Thank you, 

    Delaney