Lead acid battery tester

Hi,
I bought yesterday a battery for my UPS at a shop that specializes in batteries. I had my old battery there, so to get the same type, and I asked the chap if he had a voltage meter. Something like that, he said. He brought out a special meter with huge clamps, attached it, and said the batter had 13.6 volts. Then he tested "load" and said said the battery gave out only 20 out of 100. I don't know what he was actually measuring, some time of current over a resistor measurement, I suppose. It is adjusted for the size of battery.
Do you know what meter could be that thing?
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Cheers, Carlos.