At 19D 1A-1 4 block charging area two employees went to put a 650 scoop battery on charge. Mistakenly hooked up a 636 ""Y"" jumper to the 650 batteries, shorting the batteries. Sparking and a small flame occurred for less than 10 seconds until extinguished with a handheld fire extinguisher. Process continued a dozen times until the battery leads were cut at approximately 10:55 am.