Audiox

Hi guys ! im new to This forum! I have a nissan silvia ps13 with sr20det. The problem is that it will not start. Frist i checked the battery, and fond out that it was totalt dead, and bought a new one. When i put the new battery in, and turned the key, Nothing happend accept the full pump run, and got lights in the head lamps. A few days later i came back and Tried to start it up again, but now Nothing was happening! I checked the main Fuse (75amp) and it was broke, also a engine contackt Fuse (10amp) was broked Aswell, just changed Those fuses, and measured the battery to 11.64volts, Then i put the battery in again, and conected the positive and negative, and measured it to 1.54 volts?!?! Disconected the negative pole and then it went up again to 11 volts?! What is happening???