You shouldn't have any concern with load-testing your battery, just take the cell caps off, and don't make any sparks around the battery. I have heard reports of load tests causing an explosion, but I have never seen it happen. Connecting a charger with it being turned on, or getting a spark while connecting booster cables often will cause a battery to blow.
The usual current load on older batteries is three times the ampere-hour rating. The ampere-hour rating is different between 6-volt and 12-volt batteries, so there is a difference in current load. A typical 6-volt battery is about 100 AH, a typical 12-volt is 60 or 70 AH, 70 being at the higher end of the rating for passenger vehicles. If you don't have the proper load tester for that purpose, find a shop or auto supply that has a proper load tester to do the test for you. The typical load testers you find for sale in auto supplies are not very good for that purpose.
Batteries presently are rated in cold cranking amperage, CCA, but there is conversion from AH to cranking power for a load test; I don't remember the conversion at the moment.
Any time you are making connections to the battery, especially one that is discharged or believed to be faulty, you should take off the cell caps and make sure the electrolyte/liquid level is at the full level. That way if you strike a spark and set off the hydrogen gas, the result will be less devastating. If there is such a thing with a battery explosion.
Harvester
