Sealed batteries can't be gravity checked. If you've got a vehicle handy to install the battery into, try spinning the starter for 15 seconds with the ignition disabled so it won't start. After that time, while still cranking, the battery terminal voltage of a good battery shouldn't drop much below 10 volts. It's a quick and dirty shade tree load test, but it works pretty well.
Jerry
That is a great backwoods test for those of us without battery load testing equipment. Thanks Jerry.
