This HP laptop, model DV2125NR, running XP Media Center, cannot boot from its battery, alone. Yet, the battery is known to be in good condition and fully charged.
To make matters more interesting, the laptop can boot with only its AC adapter (that is, without a battery installed), and can boot with both the AC adapter and the (good) battery installed. But not from its battery, alone.
The battery-only configuration does permit the CPU fan to run (airflow present), does permit the hard drive to run, and displays operating LEDs. However, the machine simply does not go into the boot process. I suspect the laptop fails to sense the battery has a full charge, so perhaps the charging circuit interconnection is faulty, in some way.
In addition to the original battery, a second (new) battery was purchased to aid in diagnostics. However, that battery, when fully charged and used in a battery-only configuration, does only what the original battery does-- runs the fan, but halts the boot process after the splash screen.
When installed the new battery, attached the power adapter and started, I abruptly disconnected the power adapter at the moment the system reached the HP logo screen, and the machine continued into the XP desktop display. With screen display of the new battery charge level at 100 percent, I was able to run an intensive operation like AV scan with only the battery. After 20 minutes of operation,. the battery was at 84 percent.
Because this machine also has overheating issues, I shut down at that point. The CPU temp had reached 165F, and I definitely do not want to play with that situation. But once I have cleaned the machine of all dust (fan has been verified to run), I can explore the situation further.
Any ideas on why the laptop does not boot from a new battery?