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.