PPCGeeks - Alert during charging ?

I'll start this by say with the exception of the GPS not working quite right the Epic is awesome, I just upgraded from a touchpro 2 and its SO much faster I can barely believe it.

Now on to my question, when charging my phone shortly after plugging in the charger (5 to 25 minutes) The phone emits a double warble kind of alert. If I look at the phone its not completed charged nor is there any kind of visual alert. I would have thought that maybe it would have some kind of onscreen note as to why is does its little warble. Anyone else getting this or even better anyone know what this is?

In Winmo on the TP2 the phone would sometimes meep while charging and say the usb power source was not sufficient to charge the device. I thought this might be similar, but the phone charges no problem and is always ready in the morning.