2 Cells Nimh battery charger

Ignacio Camauer

Prodigy 20 points

Hi,

I want to build a 2 Cell Nimh battery charger (using a USB power supply)

I am going to use the 2q2002 IC and I want to adapt the dv2002l2 board.

(http://www.ti.com/lit/ug/sluu007b/sluu007b.pdf)

I believe I just need to change R9 to 100K and R7 to 2,7 o 3,3 ohm so as to charge the batteries with approx 400mA.

Would this be enough? Or should I change something else?

Thanks in advance for your feedback.

Best Regards,

Nacho.

over 12 years ago

0 Charles Mauney over 12 years ago

TI__Mastermind 31120 points

Yes, one should set the max cell voltage to 1.75V/cell or 3.5V for two cells.

0 Ignacio Camauer over 12 years ago in reply to Charles Mauney

Prodigy 20 points

And how should I adapt the circuit to do that?

0 Charles Mauney over 12 years ago in reply to Ignacio Camauer

TI__Mastermind 31120 points

The data sheet says to use a 50% divider for 2 cells. The internal reference is 2V and a 50% divider would set the MCV at 4V. I would use 3.5V MCV or a 100k on the bottom resistor and a 75k on top.

Battery voltage and temperature are monitored for maximum allowable values. The voltage presented on

the battery sense input, BAT, should represent a single-cell potential for the battery under charge. A

resistor-divider ratio of

RB1/RB2 = N - 1

is recommended to maintain the battery voltage within the valid range, where N is the number of cells, RB1 is

the resistor connected to the positive battery terminal, and RB2 is the resistor connected to the negative battery

terminal.

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2 Cells Nimh battery charger