New battery will not fully charge

Question

I have a DV6113 laptop from HP. The original 6 cell battery (2 years old) would not hold a charge. I bought a new 12 cell battery and installed it. It will only charge to 45%. What do i need to do to get it to charge to 100%? I have let it charge overnight and then fully discharged it and still it will only charge to 45%.Thanks for your helpDave