Last week I used Juno leads to start the cosworth which started no problem. Unhooked the leads and let it idle to temp fans kicked in car running fine. Fans kicked in twice more i was just about to go a run to charge the battery then all of a sudden the car cuts out no lights on the dash nothing. Put the leads back on car starts easily it runs fine but within 5 mins it does the same thing. Immobiliser led flashes really quickly along with what sounds like a relay near the ECU. Been told it's the battery that's fucked before I go buy a new battery has anyone had same problem.