Ryobi MSBC-2400 drill charger fault?

I have a problem with my 24v Ryobi charger in that it will charge initially on the red light, then after about 5 mins or so it blows the fuse.If you change the fuse or put in a different battery the same happens every time.I have probably only used the charger 20 times prior to this happening?

Any help would be appreciated.