"The Safe External Battery Pack by Barska is the perfect accessory for your Barska Biometric Safe. In the event of battery failure, this External Battery Pack can be used to access the safe by plugging it into the Biometric Fingerprint Module on the safe. The Battery Pack will then supply power to the Barska Biometric Module, allowing you to access the safe with your registered fingerprints to change the batteries. The Safe External Battery Pack provides a quick way to access your Barska Biometric Safe in the event that the batteries go out. Simply plug in the Eternal Battery Pack to the bottom of the Biometric Fingerprint Module and use your registered fingerprints to access the safe and change the batteries. Use of the External Battery Pack will not reset the fingerprints that have already been stored in the Biometric Module. Uses 4 AA batteries, not included ."