Put a piece of closed cell foam under the battery or between strap and battery.

Thanks, I checked my stash but have nothing thin enough.  I do have a collection of rubber grommets about the right thickness.  I could put one of those in each corner of the battery tray.

I would want something to spread the load out a little more on the plastic case than the four corner grommets.

I've seen cardboard used to make battery spacers. Not saying it's right, just saying I've seen it.

Go get thin piece of plywood from hobby store. Paint it black. You can get it as small as 1/16. Hobby store as in model airplanes

Thanks for the suggestions.  I like the idea of some cushioning under the battery to reduce vibrations.  Looks like 1/4"  thick mat of some type could work 

My PC680 was a little shorter than the stock battery, and a different connection meant the positive terminal cover did not fit.  A section of bucket lid took care of both issues.

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