hi I've got a 1.8 audi a v5 2000 model petrol the car was diving fine the battery went flat because of the radio tried to put my other cars battery in to start it it wanted to start but doesn't start

first off don't spam Your question, it will get responded to if your patient. And what do you mean your radio killed your battery? did you leave the power on or something ? and the battery from your other car is probly not got enough cranking amps to start the car. Put your foot to the floor on the gas and pump while trying to start it should start if its chooking already.

Yes sir we left the radio on

battery above 12.6v, if it can take load there is no reason for not starting

there defiantly is. Have you ever wondered why battery's come in varied sizes? its not so they can fit into tighter places its because battery's produce a certain amount of cranking amps. If you have to low a cranking amp the car simply won't start. 12 Volts only represents the type of charge and how much charge there is in a battery. useing the proper parts for the proper car is the only way you should do things. Charge up or replace the battery with a proper battery that is ment for the car then try it again. if it still does not start clean your maf and check the crank case breather hoses. They are the plastic tubes attached to the heads. They after a while can get gummed up and cause the car not to start.

do u understand LOAD?????

Thanks alot sir I will definitely try that thank you