Quick update. I tested the battery with the car running and it was reading under 13v. This was with the probes of the multimeter on the connectors that bolt on the battery. Then i stuck the probes in the actual copper wire of the main battery leads and the reading went up to 15V. I did this a few times and it was the same each time. I'm thinking the starter may have worked by chance when i tested it before. Does this mean i need to put new crimped connections on the end of the battery leads? The outer wiring of the leads could be corroded as somebody said before i think.