Battery is Fully Charged, But Cannot Power The Phone - Any Advice?

I purchased an extended battery, a Motorola branded BP7X for a Droid 2 phone. It's rated at 3.7 volts/1820 mAh. I tested it with a volt-ohm meter and got a reading of 4.2 volts.

When I install the battery in the phone and connect the charger (phone is off), the charging graphic shows the battery is fully charged. I can power on the phone with the charger attached, but as soon as the charger is disconnected, the phone dies. I tried this battery in two Droid 2 phones and got the same behaviour. Is this an indication the battery is defective, or is there something I need to do to make the battery work?

Thanks in advance for any ideas on this

Battery is defective if it happens on both phones, usually you should not do anything with battery it hsould just work or else there some notice on it.