So as to not confuse the masses, there are several terms here that need explanation and a little tie to FRC robots...
CCA is
Cold
Cranking
Amps and is measured at 0 degrees F for 30 sec and is rated by how many amps during this test will bring the battery down to 7.2 volts. Wholly meaningless measurement for our use at normal indoor temps. Small batteries do not specify CCA for most manufacturers.
CA is cranking amps (@32 F degrees) in car battery specs but is charge/discharge rating in our battery specs. Not the same measurement! 1 CA~1 Amp Hour. For our 18 amp hr battery this is 18 amps but measured at 25C.
Amp Hour is a rating that specifies how long the battery will deliver current until the terminal voltage reaches a certain level (@25 degrees C and that level varies from manufacturer to manufacturer.) It does not specify the max current nor does it indicate a time at any current other than that shown. It is typically measured at 1/20 of the amp hr rating. That is an 18 amp hour battery delivering 1/20*18 amps= 0.9, amps will take 18 hours to reach ~8 volts. At higher currents, the time decreases. An Enersys is speced at only 6.5 minutes delivering 54 amps continuous to fall to 8 volts terminal voltage.
Internal Resistance is an equivalent resistance that causes the terminal voltage to drop in proportion to load current. This is due to the voltage drop (Ohm's Law) across the internal resistance. This resistance varies with charge, temperature and age. A typical new, fully charged, robot battery will have 0.011 ohms of internal resistance or about the same resistance as 11 feet of #10 wire.
Battery Testers of this type
http://www.mcmaster.com/#battery-testers/=o19fra use high current loads, 60 and 125 amps or simply 125 amps and produces a meter deflection to show good or bad. A car battery (.003 ohm) has an internal resistance typically 1/4 of our battery (.011 ohm) so this tester will not give you a good idea of the state of the smaller battery. I cringe at teams that use this battery tester as it will continue to load the battery as long as the switch is held "on" which under certain conditions can damage the battery.
The Battery Beak as stated above makes two quick measurements, one at 1 amp and one at 18 amps and uses those measurements to calculate the internal resistance and from there an indication of battery state. If a cell is dead or shorted, it will show up during this test. If the cell is reduced capacity, it cannot show it as it takes some period of time for the cell to discharge. Only a long term test can reveal reduced capacity. Fortunately, this type of battery failure is rare and usually is a result of rough handling (dropping). I have seen defective cells capable of producing current for half the time other cells produce. These batteries will reduce by 2 volts for each bad cell, their terminal voltage
under load. A no load test (open circuit voltage) on these batteries will show good.
Long term testers such as the CBAIV will show all of these issues and you can vary the load and conditions to use it to test other batteries as well. The down side wilth any long term tester is the amount of time it takes, and that it must discharge the battery to perform the test. (See above post)