Help please battery flat need to open doors

[AIF]

My battery seems to have gone flat despite a battery conditioner being attached. Condition light on charger started flicking between green and amber yesterday and turned to amber today. Any ideas why the sudden failure? Also I need to open the doors; the roof is off so I can climb in but the windows are up so although I can pull the door release the windows stop the doors opening. How can you get round this?? All replies gratefully received.

[lowest]

Connect a battery to the connection points under the front of the car just behind the front passenger wheel.

[AIF]

Thanks, so simple when you read the manual!!!!!!