Had a similar crash when I put in a motor upgrade. Had a thin ply battery tray with a velcro strap to secure the battery, but no velcro on the ply itself. Strap wasn't tight enough, when full elevator was applied on throttle up and takeoff the battery slid to the rear, causing a violently tail heavy condition.
Plane came down noseless with the wing popped out of its saddle.
Repaired and flown again many times since then. Velcro on the ply tray now as well as the strap.