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NiMh buck/boost battery charger

Marcelo Lorenz
Prodigy 10 points
Other Parts Discussed in Thread: BQ2000, TPS40210

Hello.

Marcelo from Argentina.

have some IC to enable charging a 12V NiMH 3500mAh battery (10 cells), with an input voltage 10 to 25VDC? so the circuit would need to function as buck-boost

thank you very much and excuse my English.

marcelo lorenz

  • 0
    TI__Guru**** 150950 points

    We do not currently have any buck/boost nickel charger reference designs.  So, you will need to boost your voltage first and then use the bq2000 to charge your pack.

    You will need to boost to at least (10 * 1.8V) / 90% = 20V to charge this pack with the constant current it requires.  The 1.8V is for a maximum per cell voltage and the 90% accounts for the maximum duty cycle and losses in a typical buck charger.  These exact numbers must be confirmed with your charger of choice and verified in the lab.  A higher voltage will give better constant current performance which is required for accurate fast charge termination.

    You can use the TPS40210 as either a boost or SEPIC to get your input to the desired level.