At >40ºF the LiFe batteries have about hit the lowest real world temperature before the rider has to start making changes to their starting procedure. By 30ºF all most all LiFe users will notice that the battery isn't delivering 100%. Shorai's propaganda claims that their battery will perform normally until around 20ºF and then the battery may need to be 'warmed up' before it will spin up the engine at a more normal cranking speed. Shorai does continue to work on the cold cranking thing (not calling it an issue or problem) so the next crop of batteries may perform better than the ones we are writing about today. As bigj' notes, the engine and starter design (electrical and mechanical gear advantage) will make a difference to the point where the battery will appear to be flat.
Battery testing has industry standards for all aspects of battery performance. Cold Cranking Amp testing is defined by standard SAE J537. This testing procedure specifies the battery preparation and the actual testing for the CCA value. The SAE J537 CCA test mandates that a fully charged battery is cooled to 0°F for 24 hours, then while at 0°F apply a high-current discharge that simulates the cranking of an engine. A 210 CCA battery would need to supply 210A for 30 seconds and battery voltage must stay above 7.2V (1.2V/cell) to pass. If it fails the test, the battery has a CCA rating of less than 210A. To find the CCA rating, the test must be repeated several times with different current settings to find the point where the battery passes through 7.2V line. Between each test, the battery must be brought to ambient temperature for recharging and cooled again for testing.
Note in the battery testing video in an earlier post; they were loading the battery until voltage dropped down to 9.0 volts, this is not a valid CCA test. As much as the maker of the video derides Shorai for 'fake claims', their test does not actually test the battery to the J537 standard. Also, note that the LiFe has a nominal cell voltage of 3.2 volts whereas a PbSO4 battery has a a cell voltage of 2.04 volts. The J537 standard is written for a PbSO4 battery where during a CCA test the voltage is allowed to sag to 1.2 volts per cell (40%). The LiFe battery starts off with 3.2 volts per cell so it is actually allowed to discharge to a significantly lower voltage which is actually unfairly stacked in favor of the LiFe battery to show better CCA numbers. The LiFe battery is allowed to discharge nearly 70%.
Batteries have two primary electrical attributes, battery capacity and Cold Cranking Amps. Battery capacity is essentially how much current the battery can provide over a protracted length of time. Battery CCA is how much current the battery can deliver over a very short length of time. It is an issue to get batteries to pass extremely high current, this is one of the areas where battery design enters into design black magic that sets one manufacturer apart from another. All the various LiFe manufacturers will have their own recipe for how the battery pole pieces are doped with trace elements and how the cells are electrically strapped together. These two design features make a world of difference in how and how much of the huge slugs of current which is needed for starting can be delivered out of the battery terminals.
LiFe batteries have a higher cell voltage which will spin starter motors faster for an easier start, are lighter, in theory will last longer and perhaps most significant for people where it gets hot, LiFe batteries should not degrade the way a PbSO4 battery will.
