I've always heard that one should never store a battery on concrete. Apparently that is no longer true.
In case anyone is interested in buying a float charger; I went to Harbor Freight, yesterday and bought two of them on sale for $9.99. One for my Big Horn battery and one for my mower battery. Wouldn't you know it, I got an ad in today's HF circular with a coupon for $4.99. Always a day late and dollar short.