[ZeroID (Brent)]

Rainy day project.
I decided to make up a battery eliminator for the 450D. I've got a suitable wall wart ( 7.2v dc ) and was pulling apart one of the old batteries to modify as a connector for the external supply.
The battery still had some life and I was checking which connection was which and noticed it had a small circuit board inside and three links to the battery. This appears to be a mid voltage connection providing about 3.6 volts and is present on the centre pin of the connector.
I had assumed I only needed the 7.5 v to run the camera. Is this extra voltage required or is it a battery check to ensure the right parts are used?