Hi
so if i use the second flashlight(the one that uses pwm) with only the lower mode,does it affects different on the batteries compared with the first flashlight?(discharge time?too much load on the batteries?)or the affect on the batteries will be,exactly,the same on both cases?
thank in advanced.
I found this an interesting question and spent quite some time searching for the answer with no luck. At least, I found no answers from authoritative sources. There are responses relative to lead-acid batteries as used with photovoltaic and wind turbine generators. They have a similar problem, in that the principal current drain is usually an inverter, which provides a pulsed drain. In brief, there are some effects both good and bad, but I did not feel the results would apply in this example with a semi-paste electrolyte, relatively high internal resistance, alkaline battery. I will also suggest two experiments for you.
First, one could go on and on about the chemical cause of rapid deterioration from too rapid discharge. With lead-acid batteries, stratification of the electrolyte can be shown, and there are experiments that use a continuously flushed electrolyte to mitigate that. In your case, the question becomes whether the local changes caused by high current are averaged out during the no-drain time and end up no worse than what the average drain will produce. Since with heavy use, internal resistance increases. You have something to measure.
Experiment #1: Test the internal resistance of the PWM'd cells and compare that to the internal resistance of the non-PWM's cells after comparable total drain. I suggest current-time discharge of about 30 to 50% of the claimed capacity of the non-PWM cells. Try to keep the cells cool.
Second, one major cause of early deterioration is heat. Heat comes form two sources: 1) the exothermic chemical reaction during discharge; and 2) Ohmic heating by the current (W = I^2R). Obviously, the heat produced by twice the current over half the time will be more than the heat produced by a steady drain. The net effect of both processes may be complex to predict, but you can measure the result.
Experiment#2: Put each flashlight in an identical, separate, and insulated container with the same amount of a liquid (water is probably OK). Be sure to disassemble and dry well afterwards. Measure the temperature of each during equivalent discharge and see whether they are the same.
If you do the experiments, please post your results back here.
John