[twodogs]

The connectors at the battery terminals are actually fusible links. Have you tested these? Put CAL Fuse into the search box (top right) on this forum.

 

[twodogs]

Either that or a heavy duty fuse. Wrong model but does this help at all. Look at the rear of the battery housing. Not easy to see.

Renault Grand Scenic (2004 ? 2009) ? fuse box diagram | Auto Genius

otherwise, are you sure 12V is getting to the starter motor when necessary.

EDIT: Ignore this, bad advice. The post below might be more useful.

 

[twodogs]

This might help

http://www.renaultforums.co.uk/17-e...8801-2010-renault-grand-scenic-iii-1-5-diesel-starter-motor-relay-location.html

 

[twodogs]

Welcome to the world of Renault. Maybe it is time to get the multimeter out and check the 12V supply (or continuity) from the starter back to the battery.