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Charging Lead Acid, Gel, AGM Batteries

Piotr Durys
Prodigy 10 points
Other Parts Discussed in Thread: BQ24450

Hello TI,

I have a question according my problem. In my new project I have to build circuit to charge two 12V Lead Acid, Gel, AGM batteries pack connected serial to get 24V. charging limit current is 500mA. I also need possibility to check capacity, Overcharging protection and cell balancing. Which TI IC I can use to get my goal?

Thank you for your support

Piotr Durys

  • 0
    TI__Genius 13700 points

    Hello,

     

    What capacity are these cells because with a charging current of 500mA it could take a while to charge if they are any appreciable size.

     

    The other question is what is providing the power to charge these batteries? The fact that they are stacked in series raises the battery voltage and as a result it will require a higher input voltage to the charger and charging IC needs to be selected to account for this.

     

    With a 500mA charging current you could easily look at either a linear or switch-mode charger.

     

    To check capacity I would recommend measuring the voltage of the battery through a voltage divider with an ADC and have a look up table that correlates battery voltage to state of charge. Lead acid batteries have a more linear voltage to state of charger relationship making this a viable solution.

    Over charging is a voltage issue for Lead Acid is is defined by the voltage that you tell the charger to charge to. If the bulk voltage is set correctly and the leads to the battery are proper sized you should not have an overcharging situation.

    I would recommend looking at the bq24450.

    For cell balancing it will be easiest to do this passively using parallel resistors and measuring the voltage across the two packs and using a switch to selectively discharge the pack with the higher voltage.