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NiMH 12 "D" Cell battery pack: Charge and Control Design Approach

Andy Chernock
Intellectual 740 points
Other Parts Discussed in Thread: BQ2000, BQ2000T

I'm looking for suggestions on how to approach a design that will control and monitor the charging of multiple NiMH battery packs.  Where each pack contains 12 rechargeable D cell NiMH batteries.

Is there a block diagram or reference design that will help me get started??

 

Current working environment:

One 12 NiMH D Cell battery pack connected to a Battery Charging board via a 4 wire interface:  Batt+, Batt-, Temp+, Temp-...where the Temperature is monitored by an attached Thermistor.

 

Requirments:

Insert a "test board" between battery pack and Charging board to determine: 

(A) Is charging board functioning properly:

(A.1) When Charging board notices a low battery charge, does it properly attempt to charge the batteries?

(A.2) When Charging board notices a fully charged pack, does it properly stop charging the batteries?

 

And (B) Is Battery Pack functioning properly:

(B.1) Will Battery Pack hold a charge?

(B.2) Does Battery Pack overheat when charging?

 

Additional Features:

C.  Expandable to test 1 to 10 Battery Packs at a time (in parallel)

D.  Auto detect Battery Chemistry (Current battery is NiMH, but future development will include Li-Ion batteries)

  • 0
    TI__Guru*** 148130 points

    Please look at the bq2000 and bq2000T.  These are switchmode nickel and lithium chargers (it auto-detects between the 2) that can charge any number of cells in series.  You would then use 1 to 10 of these ICs, running off the same input voltage, to make the system expandable.

    These ICs start charging on the insertion of a pack, stop charging when the pack is full, include a timeout function for detection of a pack that doesn't retain charge, and contain a thermistor input to detect a safe pack temperature.  The 'T' version uses a dT/dt termination vs. PVD.