Dell Latitude E6400 battery problem

Hello from Bulgaria,

I have a Dell Latitude E6400 whit 6-cell battery , one time is message me to replace battery because is poor quality.  

When is charged on 100% the battery is run only 30 min and laptop is shutting down  , then i power on again and whit 2% battery is running above 20 min. 

after shutting down total :) OK i replace whit new 9-cell battery from china , 

but same problem whit on line time on battery :(  Can i have problem whit my computer not whit batteries ?