battery problems

hi all .all of a sudden my battery is losing its charge took her out for a run on saturday havin jump started her everything fine started her a few times that day all good .went out sunday battery dead  . Was messing about with spark plug leads before this was starting to happen anybody any ideas me whats going on .cheers

Have you done a basic test on the alternator?

no sorry dont no how to .how do you test it ? Cheers

A basic check would be to compare the voltage of the battery when its not charging (ie engine off) with the voltage when it is (engine running and red battery light not illuminated). It doesn't give the REAL indication of it charging, the only thing what will do that is an ammeter, but its a basic check which often shows the issue.

also make sure the battery light comes on with the ignition and goes out once engine is started. if not that means the blue wire is disconnected and the alternator wont start charging the battery unless it is revved.