As pointed out by others, regular batteries are 1.5V, and rechargables are 1.2V. The batteries in the NG are in series, so stds provide 6.0V, and rechs provide 4.8V. The system needs to know which type are being used, so it can adjust its voltage expectation and not consider 4.8V to be a low battery condition.
Ideally, a manuf would provide a switch for this purpose. In Philips case, they'd rather not provide this switch, and instead charge a lot of money for 4 rechargables wrapped in plastic with a connector, and a charger.
The best way to use your own rechargable batteries is to find out how the Philips battery pack signals the NG that rechargables will be used, and do that yourself.
I've looked at the 3-pin connector. Pin 1 is at the bottom, and is connected to ground. Pin 3 looks like it is the positive connection for rechargables, separate from the pos conn for std batteries. I can't see where pin 2 goes.
Would someone with the rechargable battery pack like to check it and report what's connected to the 3 pins? Also, is any connection made to the 2 spring battery connectors that remain in the battery compartment after removing the insert.
This information would allow a person to "fool" the remote and get it to properly allow for the use of rechargables.
