Why is my new battery toast?

[celica91]

Old battery of about 8 years died. I replaced it. Two weeks later, my new battery is dead. The car will jump start, and run fine, but as soon as the car is turned off it won't restart, even with 20-30 mintes of run time. with all accessories on, engine running the voltage at the battery terminals is 14.7 volts. Turned off, engine off, the battery read 9 volts. Is my new battery junk or could the voltage regulator be bad and cooked both batteries? I need to have a working car so please help.

celica91 <celica91.2m0meb@no-mx.forums.yourdomain.com.au>
wrote in news:celica91.2m0meb@no-mx.forums.yourdomain.com.au:
[color=blue]
>
> Old battery of about 8 years died. I replaced it. Two weeks
> later, my new battery is dead. The car will jump start, and
> run fine, but as soon as the car is turned off it won't
> restart, even with 20-30 mintes of run time. with all
> accessories on, engine running the voltage at the battery
> terminals is 14.7 volts. Turned off, engine off, the
> battery read 9 volts. Is my new battery junk or could the
> voltage regulator be bad and cooked both batteries? I need
> to have a working car so please help.
>
>[/color]

As Ray indicated could be bad battery. Had similiar experience
on my '94 Pickup. Battery less than a year old from Advance
Auto. Slow crank\no start in the am few weeks ago. Took battery
back after checking the items you also checked & got a
replacement for $0.88. Also seems to crank much faster &
stronger now.
dc