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Backup battery charger from main battery

Az-eddine Haida
Prodigy 25 points
Other Parts Discussed in Thread: BQ24105-Q1, BQ25171-Q1

Hi,

I need to charge a small backup battery 12V 7Ah on the car when the car is running can you help to find the proper IC and how to use it.

The battery should be always connected, so I need to keep the voltage on 13.5V to avoid battery damage when is fully charged.

Thanks

  • 0
    TI__Guru**** 165886 points

    Hi Az-eddine,

    What is the battery chemistry, LiIon or lead acid?  What is the final battery voltage 12V or 13.5V?  What is the input voltage and current available to the battery charger?  Does the charger need to automotive compliant?  How quickly do you need the battery to charge?

    Regards,

    Jeff 

  • 0
    Prodigy 25 points

    Hi Jeff,

    the battery is an SLA Battery, rated 12V 7Ah, it will be used as an emergency battery to power a small load.

    The source will be car's main battery source (alternator) i need to control the voltage that should not exceed 13.5V, this voltage is to prevent the battery from losing water during long float charging.

    thanks

  • 0 in reply to Az-eddine Haida
    TI__Guru**** 165886 points

    Hi Az-eddine,

    TI only has 2 chargers that automotive qualified:  BQ24105-Q1 up to 2A switching charger and BQ25171-Q1 800mA linear charger.  The BQ24105-Q1 needs external circuitry to protect against 40-V load-dump.  The BQ25171-Q1 is  40-V load-dump.  At only 2A or 800mA charge current for 7Ah battery, both will take a long time to charge the emergency battery.

    Regards,

    Jeff