Portable Battery Charger Ultra Mini AA Battery Powered Emergency Cell Phone Charger Travelling Backup Chargers for Android Smart Phones (Red)

This charger is what I've been looking for, finally found them, this little thing can charge phones with two aa batteries, very useful as a backup charger.

Just received this charger with high hopes. Alas, disappointment. I guess I should have realized with a price this low my expectations should have matched. Great concept (was going to use this backpacking). I have tried all the battery chemistry I have (alkaline, NiMH, lithium) but the charger emits a loud high pitched squeal from each when plugged into a device. Also the AA batteries get alarmingly warm. It does charge the phone but the noise is a deal breaker. I am going to return this charger for an exchange with the hope that this one is defective. I will update if the new one is any better.Edit: Amazon does not offer a replacement, only refund. I will not order another so there will be no follow up.