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DS2715 NI-MH Charge Controller Help

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nhoj4

New Member
Hello!
I am attempting to design a system that charges a 6 cell 1800 mAh NIMH R/C car battery wirelessly with the DS2715 charge controller by Maxim. I am trying to modify their linear charging design for a 6 cell battery.

In the data sheet they specify the circuit for charging a 3 cell pack (in series) linearly (with a 6 V supply), and I have built the circuit accordingly. The only info in the data sheet regarding changing the cell count is the voltage divider on the Vbat pin for detecting a single cell's voltage. I assume that for charging 6 cells I would double the supply voltage for 12 volts? I know that the IRF can handle this change but am unsure about the other components and do not want to damage the IC.

When I supply the circuit with 6 Volts and use the original resistive divider for 3 cells, the LED is off (as it is supposed to be with no battery connected). But, when I use the 6 cell resistive divider and supply 6 V the LED flashes at 4 Hz indicating that there was a fault. I am assuming this is because the circuit really does need 12 V. I have a LED that is suited for 12 V on the way but wanted to see if anyone has used this IC for a similar design and could offer some insight.

I have contacted Maxim for support but they have not gotten back with me yet. Thanks in advance.

Part link: https://www.maximintegrated.com/en/products/power/battery-management/DS2715.html
Datasheet: https://datasheets.maximintegrated.com/en/ds/DS2715.pdf
 
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Pommie

Well-Known Member
Most Helpful Member
The datasheet states 1 to 10 cells so there shouldn't be a problem. You say you've ordered an LED suitable for 12V but all you need to do is increase the series resistor from 470 to 1.2k.

Mike.
 

crutschow

Well-Known Member
Most Helpful Member
But, when I use the 6 cell resistive divider and supply 6 V the LED flashes at 4 Hz indicating that there was a fault. I am assuming this is because the circuit really does need 12 V.
Of course.
You can't charge a 9V battery with 6V (unless you have a boost converter, which this isn't).
 

nhoj4

New Member
Thank you, my circuit does work as intended and I did not fry the chip. Thank you for your responses.
 
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