It all depends upon the chemistry and space you have. Batteries should always be installed as securely as possible with the least amount of allowable movement.
For flooded batteries you'll need acid containment in the event a case should crack or leak, and this does happen. One battery maker recently moved away from certain case color as the additives to make the color lead to poorer weld-ability and a case more prone to leaks at the weld.
Within the acid containment zone there should be no materials that can suffer acid attack such as screws that can be eaten away thus releasing the battery, and I have seen this countless times.
Ideally batteries such as AGM and GEL & flooded too, but especially
recombination batteries, should have at least few mm's gap between them for air circulation.
Fasteners used to hold batteries down should ideally be through bolted unless the substrate is solid enough to hold screws and the batteries upside down.....
For strapping multiple batteries with one strap see below. Note how the strap dips down between batteries to yield a sturdy support for each battery without "pinching" them together. *These are AGM batteries using "
mounting trays", flooded batteries would require acid containment & the "trays", really boxes, would need to be as tall as the battery... With these straps cinched down tight into the trays these batteries have less than 1mm of
wiggle room....
These NRS straps are 1.5" wide polypropylene and nearly bomb proof especially compared to the cheesy battery straps with plastic buckles that ship with those black plastic battery boxes. If I had a dime for ever cracked or broken plastic buckle on battery box straps I've seen, I'd be retired on a beach right now sipping a Margarita... The machine screws are through bolted..
