Get a dvm, some alligator clip leads, and a load resistor. For a 48 v 840 wh battery I use a 10 ohm 1050 W resistor. For other voltages you would use other resistors.
Hook up the dvm parallel to the load resistor. Do the test outside, if there is a fire you can burn your concrete step. Connect the battery and see how long the battery maintains normal charged voltage at 5 amps. I had two **** batteries collapse to 7 and 11 volts during this test. My good one I disconnect it after an hour, no problem.
Resistance & wattage would vary for other voltage batteries. 10 ohm would only load a 12 v battery to 1.2 amps. No test at all. Flashlight batteries would pass that test.