T61p problems with autonomy

[thinkpadusert61p]

Hello! After installing new CPU X9000 and 8gb ram my T61p doesn't want to work properly on battery (turns out after 5min of usage on battery) battery is relatively new less than 2 years old 4400mah 49wh. CPU I was used on 11 multiplier(2.2ghz) on 0.92V. Is it possible somehow to use it on battery properly maybe by instaling bigger capacity one? I apologize in advance for my English, I hope my message was understandable.

[thinkpadusert61p]

Edit: also on my laptop is installed HDD caddy instead of dvd drive

[axur-delmeria]

It's possible that the battery has a dead lithium cell inside, which causes the battery voltage to suddenly drop when a sufficiently high current is drawn from it.