Hard wiring a baby monitor remote

[mzac]

Hi, I have a Philips DECT baby monitor that I purchased about 5 years ago.  Of course the batteries have failed in the remote/parent unit so I tried changing those a few months ago and now they're dead as I was always leaving it on the base turned on.

So that's what I want to do, have it hard wired and on all the time.  It normally takes 2 x AAA batteries so I tried to figure out the best way to power it.  I took a chance and gave it 5V from a usb connection and low and behold it works, no smoke!

The problem I'm having now is that this unit has some kind of low battery detection and at 3am this morning it started beeping like crazy saying the battery was dying.  There is no way to disable the beeping!

So my question to all of you is how could this unit be figuring out it has a dead battery and what can I do to fool it?  Is it checking resistance, capacitance?  Can I just put on of those across the battery terminal in line with my 5VDC alligator clips?

The model I'm using is a Philips SCD520, FCC ID is BOUSCD520H

Thanks in advance!

[mzac]

Anyone?

[nidlaX]

How did you wire it up and for how long was it working before this problem started? It's possible that there's a discrete battery charge/discharge controller chip inside that monitors the battery voltage. If you damaged the chip/circuit with an over-voltage, it could be malfunctioning. Maybe the microcontroller is receiving no battery voltage signal, so it thinks the battery is dying/dead.

I think your best bet would be to take it apart and start tracing out the battery input circuitry and see if anything has failed. 5V into a nominal 3V input might not have let out the magic smoke, but that doesn't mean the device was designed to tolerate such an over-voltage for long periods.

[retiredcaps]

Clear focused pictures of the pcb (both sides) would help.  Focused enough so we can read the writing on the chip, resistors, etc.

[mzac]

Hi, thanks for the feedback.  I took it apart and took some pictures, the last picture shows what looks like to be a bit of burned components, but not too sure...