Latitude D505 battery operation

I have recently acquired a Dell Latitude D505 laptop with a Pentium M processor and 512 MB RAM with a Wireless card in the MiniPCI slot.

Shortly after installing Lubuntu, a low-end version of Ubuntu Linux, my battery has seemed to stop working correctly. The laptop will not turn on with the battery installed, and while the unit is plugged in the battery indicator on the palm rest blinks five times with a pattern of red-red-red-red-green. After removing the battery and pressing the button on the battery itself, the LEDs blink thrice, and the LEDs are as follows each time it blinks:

Green, off, Green, off, Green

To do further testing, I went into BIOS setup and it told me that the battery was at 100% and charging. The battery was plugged in, but the last time I had shut down the computer the battery level was a couple of points below 20 (this was the first time plugging it in since then).

Lubuntu tells me that the battery is a "Sony DELL C26034" battery and that the battery is at 0% and charging. After digging deeper into the depths of Linux and looking at a system profiler, it tells me that I have no batteries installed even with the batter in the system. Linux also thinks the battery becomes fully charged after only around 2 minutes of the battery being plugged in. 

I am assuming this is pointing me towards some kind of error or malfunction. The last time the battery was in working condition, I had shut down the computer at around an 18% battery level. Is there a fix to this, and if there is, how much life is left on the battery, if before this problem the battery lasted about an hour and a half from full charge?