The amp-hour rating of a battery is time related, and as the rate of discharge increases, the capacity decreases, according to Peukert's law. If a battery has a 16 amp-hour capacity at a 10 hour rate, that means it can supply 1.6 amps for 10 hours, not 16 amps for 1 hour.
When I got my first LiFe battery 15 years ago, I bench tested it. It was claimed to be a 4 amp-hour battery, but with a 4 amp load, it took about 20 minutes to discharge to 12.0 volts, and then the voltage dropped like a rock within seconds.