The Samsung Focus appears to have a bug where if the battery is completely dead (as in, once its dead for a day, leave it in there for another week until it is completely discharged), the phone cannot charge the battery.
I have been able to charge the battery by taking it out of the Focus and putting it in other Galaxy-class phones, which do not have this bug. Once the battery was charged up a bit, I was then able to power up the Focus and finish charging the battery.
I’ve seen some posts where people would take out the battery for 30 seconds and then put it back in and the phone would charge, but it did not appear that taking out the battery out of my phone would fix the issue. I’ve taken it out for minutes at a time, and the battery would not charge.