Those tool batteries are a little pricey aren't they? I use one of these
http://www.homesecuritystore.com/p-239-bd412-12-volt-4ah-alarm-battery.aspx?affiliateid=10050&wm_ctID=359&wm_kwID =21942114&wm_mtID=1&wm_DefaultURL=http%3a%2f%2fwww .homesecuritystore.com%2f&source=pla&utm_source=go ogle&utm_medium=cpc&utm_campaign=pla
I
bought three at a damaged and overstock outlet for $3.80 each the other day.