Not used over the winter but battery charged and car started/run evey 6 weeks but today looks as if battery will not charge and car starter will not turn. Connected charger direct across battery not from underbonnet terminals. Car is 2009 so maybe battery as had its life. I've read the battery is an AGM gell type and they can be difficult to recharge if volts too low. Anyone revived such a battery, any advice on DIY replacement. Read about the need to register the fitting of a new one, but any consequences if you don't.