So this morning tried starting the car as i turn the key engine wouldn't crank and alarm went off, tried pressing the buttons wouldn't turn the alarm off, turned it off with key and reset it. As i turn the key again i noticed no engine lights turn up on the dash, radio doesn't turn on or lights, i figured it was a flat battery. But then i put my brothers battery in, car turns on etc. However i put my battery back in the turns on fine What was the problem ? cheers
Bad contact, lose connection? Did you run the car with your old battery for a while to charge it before starting again. This problem is usually to do with flat batteries.
Loose battery connection or corrosion between the terminals. Once the starter tries to draw a large amount of power the connection can sever and need to be cleaned/tightened up for it to contact again.