on some of he agricutural kit we secure the batterys with a coouple of welded on straps of 75mmx10mm steel, the only way to get them out is to cut the weld off the ends so the strap can be pulled up and battery removed in normal way, makes changing batterys a PITA but drasticly reduces need for new batterys, as the cheepest ones we use are nearly £200 it's worth the bother esp as most kit has 2 batterys