Our 4 year old v7 has stopped picking up on a full charge.  I have done quite a lot of research and cleaned the filter (approx 3 months old) and given the head and all areas a thorough clean.  The hoses, wand etc are all clean and obstruction free and the vac appears to be pulling good suction when you put your hand over it.  It has pulsated in the past but we have always cleaned it and it is not pulsing currently. Battery was replaced about 6 mths ago and works fine. 

There was only a 2 year warranty on it so we are out of warranty and out of ideas.  

Any recommendations or advice very welcome?