[brucepick]

I don't know about lawn and garden batteries BUT I've learned the hard way that apparently a few years ago they started making all the battery posts a slightly smaller diameter. So older cars (like our '04 Accord) have original battery clamps that are bigger than the posts on the stock size replacement batteries I've bought.

Solutions:
1) Ignore the poor contact of large-diameter battery clamps. At your peril.
2) Get little lead shims that are made to fit between the post and the clamp. Some are flat squares of thin lead, some are shaped like a thimble to slip over the post. That's a nice easy, low cost solution.
3) Replace the clamps on the ends of your car's battery cables. Sometimes you'll need to replace the cable.

I've put little trickle chargers under the hoods of my son's two unregistered cars that now live in our driveway. That way the batteries stay fully charged, even though they rarely run. I got the chargers for about $15 each at a big box parts store.