Looking for ideas to hold down 3 group 24 batteries.  Went from 12v to 24v trolling motor so I needed to add a battery.  I had limited space to work with so I had a tray built out of ss sheet metal that will hold 3 batteries in the one tray. I need to come up with a way to secure them.  Do you guys think a poly strap would hold them down?  Anybody got a setup with three batteries in one tray?  

Group 24 is a very common battery.  You can get the rectangle holders that sit on top and long j bolts going down to the tray.  

You can also cut slits in the tray and use heavy duty, 1" wide nylon strap to go around each one and a short 1/4" bolt/nut through both ends on top of the battery to hold them.  That's how I do mine.  I fastened group 27 trays to the floor of the battery compartment with the straps under them and pull them over the batteries and bolt the ends together.  It's been airborn over some better big waves and wakes bunches of times and they've always stayed right there.

Whatever you come up with, each battery needs to be held down independently. A solid hold down on two opposite sides will keep them in place during encounters with waves and boat wakes.