Why does a HP 6510b charge light blinks 8 times shuts down

On that particular model you need to press the power button nine additional times waiting for the light to Blink 9 times each and then after the 9th time the procedure is as follows... Press the button 4 times hold for seconds on the fifth button push then release for 4 seconds then press the button twice and it should blink 8 times repeat this procedure continuously until the button only lights up once. After the button lights only once then you are ready to place the item into a garbage bag and throw it into the dump

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices.
http://electro-medical.blogspot.com/

Did you get the charger with it? Charge the battery first before you use it.

All the time, or only when in Sleep/Hibernate mode? Is the battery charging properly? A bit more info. Shut down Sleep and Hibernate to verify.

See


http://h50146.www5.hp.com/lib/doc/manual/workstation/xw6400/364898-001.pdf



Page 110 - M/B or Processor fail.

try this: Make sure the battery for the notebook is out in step 8


the procedure to reset the CMOS/BIOS is in the maintenance and service guide on page 46.

Follow these steps to clear the password:
NOTE: These steps also clear CMOS.
1. Shut down the computer. If you are unsure whether the computer is off or in Hibernation, turn the
computer on, and then shut it down through the operating system.
2. Disconnect all external devices connected to the computer.
3. Disconnect the power from the computer by first unplugging the power cord from the AC outlet and
then unplugging the AC adapter from the computer.
4. Remove the battery (see Battery on page 48).
5. Remove the real-time clock (RTC) battery (see RTC battery on page 68).
6. Wait approximately 30 minutes.
7. Replace the RTC battery and reassemble the computer.
8. Connect AC power to the computer. Do not reinsert any batteries at this time.
9. Turn on the computer.
All passwords and all CMOS settings have been cleared.

Your Battery is basically dead. They only have a useful life then have to be replaced. Yours is at the end of it's useful life.

IF the battery is bad the charge lndicator on the laptop will flash (But not periodically) it will be a constant on-off-on-off..... Best check would be to remove the battery completely and use the adapter/charger power supply only. If it still does not turn on then you either have a bad power jack connection or a more serious motherboard problem. Also is the green light flashing on the adapter/charger or is it the charge/battery indicator on the laptop?

If this is a BIOS Lockout Password, then you would need to Pull the CMOS battery From the laptop... Which most likely means Complete Disassembly of the laptop just to get to the battery... You would have to unplug the battery... Make sure the Laptops Charging Battery is also Removed and the AC Adapter is NOT plugged in...
Once the CMOS battery is removed, Hold the power button down for 30 seconds... then replace the battery and see if it is bypassed/removed..

There is a good chance that the BIOS password is on a security chip on the motherboard and if this is the case, then pulling the CMOS battery will do you no good... You will need to replace the motherboard if this is the case...

you can get your answer here .