4 larger alkaline batteries (1.5V) such as C or D cells can be used to extend battery life using the appropriate 4cell battery holder wired to the positive and negative terminals on the RIGHT side (the side nearest to the LED) of the AA battery holder (the apparent "terminals" on the LEFT side are not actually terminals but are a single piece of metal that serves only to connect batteries number 2 and 3 in series; you can confirm this by popping out this metallic piece). D cells can last 4 to 5.5 times as long as AA batteries. If using 9volt snap connectors such as those in this video, you must keep track of positive and negative terminals rather than relying on the wire colors as using two 9volt snap connectors attached to one another leads to the red wire being unconventionally negative and the black wire being positive on one side of the connection. Alternatively, a 5cell battery holder containing 5 of any one size (AA, C or D) NICd or NiMH 1.2 volt rechargeable batteries can be used to provide 6 volts (1.2V x 5 = 6V) to the cat door. Most power adapters will NOT work with this cat door due to electromagnetic radiation/interference (EMI) inherent to switchmode power supplies that likely interferes with the radiofrequency identification circuit that communicstes with the cat's microchip (RFID). Note that I misspoke at the end of the video, stating "amps" instead of "milliamps." I have measured the baseline current and the peak current with the system powered by both 4 AA and 4 D alkaline cells and these values are the same (1 mA & 345 mA respectively, not 1A & 345A as I stated in the video) regardless of the battery size.