My new laptop battery isnt working properly

i have a old ibm thinkpad i series which is now my main computer untill i repair my desktop, i ordered a new battery and got it today, i put the battery in my laptop and it immediatly found it, but then i noticed it got to 99% awful fast, so i dissconnected my charger and the laptop just shut off just like there wasnt even a battery in it, so i went searching for another battery for it and found one at a local school's supplies closet, bought it off of them for $15 and popped it into the computer, again it jumped to 99% really fast, so now i think it is a bios problem, but i cant seem to find a bios update, it is a ibm thinkpad i-series 1120 type: 1161
please help me on determining if it is the bios and findind a bios update for me, highly appreicated