So given that it froze 20 minutes after purchasing, it's safe to assume you didn't power the phone off and charge it to 100% before using it. The problem may be related to battery charge level - that is actual level versus what the meter shows. Since these batteries are partially charged at the factory to about 50% so they don't drop into protection mode while on shelves, they don't get the chance to identify what a full charge is. This means the meter is guessing at the charge level from the moment you power the phone on.
Originally Posted by Dunc
Then there's the problem of self-discharge while on the warehouse shelves. These batteries lose power even while sitting on a shelf. So if one was packaged in November, for instance, and then you buy it in March, it's been sitting in a box on a shelf for 4 months. That 50%, could actually be 20%. Problem is, the meter doesn't know that. It thinks it's still 50%, because that's what was in the battery when the phone was last powered down. So now you go to use it as you leave the store and 20 minutes later the actual power level of the battery is technically 0%, but the phone still thinks it's 20% or more, so because the voltage is too low, the phone starts freezing for "no apparent reason". After powering down and back up again a couple times, it still does it.
Then it's rebooting on its own as well. These are all signs of a meter that doesn't know how much power the battery has and is overestimating the acutal state of charge.
From Battery University (Battery Fuel Gauge: Factual or Fallacy? - Battery University):
The fuel gauge has the inherent drawback of needing periodic calibration, also known as capacity re-learning. This is done to correct the tracking error that develops between the chemical and digital battery on repeated charge and discharge cycles. Calibration could be omitted if the battery received a periodic full discharge at constant current followed by a full charge. The battery would reset with each full cycle and the tracking error would be kept at less than one percent per cycle. In real life, however, a battery may be discharged for a few minutes with a load signature that is difficult to capture, then partially recharged and stored with varying levels of self-discharge depending temperature and age.
Manual calibration is possible by running the battery down until “Low Battery” appears. This can be done in the equipment or with a battery analyzer. A full discharge sets the discharge flag
and the subsequent recharge the charge flag.
Establishing these two markers allows SoC to be calculated by tracking the distance between the flags. For best results, calibrate a device in continuous use every three months or after 40 partial cycles. If the device applies a periodic deep discharge on its own accord, no additional calibration will be required. Figure 1 shows the full-discharge and full-charge flags.
Notice the discharge flag is NOT at 0% like many people try to convince the forum, but at 10% in this example? In the RAZR, it's 15% for good measure.
So for us, a full charge at 100% with the phone off, followed by usage at a normal rate until "low battery", followed by another full charge and you'll have a proper level calibration. My bet is you wouldn't have suffered the issues if this had been done first.