My battery wont switch on the laptop

Hello guys!
I happen to open my Acer Aspire ES1-512 and disconnected all th parts on it including the Cmos battery as i wanted to clear the Bios password on it. Upon my putting it together i have realised that the battery wont switch on the laptop again. When i connected the charger it switched on and i went to the battery icon on the monitor and i got shocked caz the battery is on 95% BUT wen i removed the charger the laptop goes off instantly. Am very sad, worried and hopeless caz the laptop is very fresh and the battery could last for 3hrs and more.
Would you somehow recommend me to buy another battery or there is any other way i would help the situation.
Thank you in advance
Highly stressed Hommann