Motorola Droid :: Weird Battery With Multiple Roms / Kernels

Some weird things are going on with my battery. I was running Liquid Froyo 1.9 and even 1.95 using slayher kernel and i even tried the p3droid kernel and when i reached about 40% battery, my battery would just jump to 20% and after that pretty quickly to about 5% and then its dead. I recently installed ultimate droid 2.0.0 also using slayher and even then it still did it. I don't understand why this is happening, i havn't even used my phone that much for it to reach 5% so fast, especially jump from 40 or 50% down to 20% in an instant.