Hi Justin Case,
Post #56 is sort of the pre-face for how I built the chart and came up with this concept of "heat factor." When I actually sat down and started punching out numbers (pages and pages of calculations), I made adjustments to account for more variation in cell condition and age, basically, I moved conservative.
Finding the heat generated within a cell at a 2C discharge rate is pretty much just a function of calculating for power distribution within a series circuit based on resistance in each part of the circuit. The cells represent a certain portion of the resistance of the entire circuit, so as long as the resistance of the cells is a known value (I tested and studied and came up with a value), and the rest of the circuit is a known value (pretty easy to calculate with a few known operating conditions) we can calculate the amount of electrical energy will be lost to heat within any portion of a circuit.
For calculating "heat factor" the exact resistance of the cells isn't super critical, as long as you use the same constant for all calculations things will come out about the same.
For each bulb, a snap-shot of a theoretical point during a discharge under PWM regulation is created. The snap-shot calculates the amount of energy that goes to the bulb, and the amount that is lost to resistance in the cells.
When the amount of energy converted to heat in the cells rises above the amount calculated for a normal direct drive 2C discharge, the "heat factor" rating goes above 1.
The maximum continuous run recomendation is the estimated total run-time divided by the square of the heat factor.