Power coming from batteries but won't start and makes loads of clicks?

You charge the battery - or get a new one.

The clicking is the starter solenoid operating but the battery is so weak there is not enough power to turn the starter motor and the engine - the battery voltage drops to be close to zero - consequently the starter relay drops out and the voltage comes back up and once again the starter solenoid operates - and so it goes on click - click - click.

Good Luck...
August 2015