Problem with phone randomly resetting

[BB454]

Hey guys, I have what I'm hoping is a simple problem and also hoping you guys are able to help me pinpoint the cause. I've owned the phone a while (over a year I believe). I regularly use my BB to listen to music in my car (the quality is so much better than CD's, not to mention it saves a lot of blank discs). After a while, I noticed my battery would die fast. I would wake up around 6, take it off the charger and it'd be half way dead by afternoon. I'd never seen it do that before. So one day I went to the grocery store and by the time I was home my phone was asking to be charged (It was near dead with red light and warning). Just as I reach the charger it dies, and continues to reset itself with a red light and a hourglass rotating for hoursssss even while on the charger. Finally came back up and I figured I was good to go...
False. Either my phone is wrecked OR the battery is wrecked. I don't want to waste $200 on a phone if it's only a $50 dollar battery. Similarly, I don't want to waste $50 on a battery only to find out I need a whole new phone. So here's what is currently happening. I can leave it in my pocket all day and check messages (I've stopped listening to music on it) without any problems (normal battery drain etc). BUT if I use it to make a phone call or attempt playing word mole which is highly addictive, it will die and start rebooting itself with the red light and the hourglass thing again. It will do this UNTIL I put it on the charger where it will stop soon after and boot up normally. So I'm thinking it's just the battery but I'd like input before I buy one in case it's the phone itself. Thanks in advance for all who help.

[BB454]

Anyone? I can provide more info upon request. I did a security wipe yesterday and as my contacts were being re-added (Backup Assistant), the phone did it's reset thing again. One more thing I noticed is that when it does finally come back up, the battery is fully dead. I know that a restart takes around 10% of the battery, but it will die with full battery and come back up with none. It's weird because this morning when I pulled it off the charger (it'd been charging all night) it worked for a few minutes and then reset. So at this point I'm lost. This has been the only problem to date I've had since owning my blackberry.

[MissoulaMarinerFan]

I'd just go with getting a new battery. You can get them for like $20 here on crackberry.

[pearlyrob]

I had the exact same problem. It would just randomly reboot and keep rebooting until the charger was connected. I switched batteries with my wife and it worked, so I bought a new battery off ebay for 15 bucks shipped and its been over a week and it works like new!!