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BQ2000 charging questions

Terry Jendon
Prodigy 245 points
Other Parts Discussed in Thread: BQ2000, BQ24400

I have a customer looking to use the BQ2000, in a new audio product.  This product will be powered by 2 AA batteries.  They had a couple questions:

 1)       Can I use the BQ2000 to charge both batteries in series?  I assume I simply need to use a resistor divider and connect half the overall battery voltage at the

        BAT input.

2)       The customer wants to know if they can be able to use alkaline batteries, as well.  How does this charger respond if alkaline batteries are installed?  Are there any safety issues?

3)       I do not plan to install the temperature sensing resistor, but am still concerned about safety issues.  If I were to limit the charge current to roughly 50ma, could I be assured that a faulty battery would not present a fire hazard?

  • 0
    TI__Guru**** 150900 points

    I assume the 2 AA batteries are nickel chemistry?  The bq2000 will charge nickel or lithium cells only.  If only nickel cells need to be charged, the bq24400 will provide the same functionality as the bq2000.

    Yes, the bq2000 can charge 2 series nickel cells.  Simply adjust the voltage divider on BAT.

    This charger (and no other charger that I am aware of) is specifically designed to not charge alkaline batteries.  If an alkaline battery were installed, most likely its voltage would very quickly ramp up as charging began (since the alkaline battery is very high impedance when being forced to accept charge) and trip the maximum charge voltage.  This would quickly end charging.  Also consider that there are millions of nickel batteries and chargers in the world and alkaline batteries can fit in those, as you noted.  When is the last time you heard of somebody putting an alkaline battery in a nickel charger and it catching fire, etc.  I don't ever remembering of hearing such a news story.  This is not a safety issue in my opinion.

    Yes, you can use the IC without a temperature sensor.  Just be sure and bias the TS pin to the proper voltage to allow charging.

    Contact the battery pack manufacturer for the safety of their pack during the fault condition that you are concerned about.  For sure, it will depend on what C rate 50 mA is.  Charging at less than C/10 may be ok for your pack.  Also, these ICs have a charge timer for fast charge and top off in them.