I have a Dell Latitude 5500 laptop. With the power cord connected, it boots and runs fine. Once booted, I can disconnect the power cord and run from the battery for a few hours. No problem.
However, I cannot boot the machine when running on the battery, even when the battery is fully charged. I get the kernel selection screen, but the encrypted drive password never comes up. I just get a blank screen.
If I connect the power cord, it boots just fine. If I disconnect the power cord while it is running, the system runs as expected on the battery.
So, my battery is fine, and I can run with the battery as expected. However, I cannot boot when on battery power.
When I first got the laptop, it had Windows installed. When Windows was installed, it booted on the battery without a problem.
This is the strangest thing. Any ideas?