Curious_character
Flashlight Enthusiast
- Joined
- Nov 10, 2006
- Messages
- 1,211
NiMH and lithium cells deliver nearly the same amount of energy regardless of whether it's extracted in small doses, or in a continuous slow or fast discharge -- within reason of course.
Alkaline cells, however, don't. They deliver a lot more total energy at low currents than they do at high currents, and a lot more if discharged in small doses with a rest in between.
So you can often get a much longer total run time from an alkaline cell powered light if you use the light only for short periods of time with a rest between, than you can if you just turn it on until the battery goes dead. Most of the run time graphs show only the latter case, which might not be the way you typically use your light, so you can easily get a pessimistic view of the amount of total run time you could get in practice.
I recently recorded some run times for a Kai Domain "Buckle Light", which draws a very heavy current from its AAA cell supply. Not surprisingly, it doesn't last long at all when run from an alkaline cell -- at least not if the light is kept on constantly. But after running the light until the light output was very low, I turned it off and let it sit for about 18 hours. Then I turned it on again with the same alkaline cell still in the light. The result was quite a bit more run time at a lower but still very usable light level. About 24 hours after that, I did it again, and got several minutes more. Although you can get even more by using the light for short periods of time with rests between, this test shows the ability of an alkaline cell to recover somewhat after even running the battery nearly completely down. You can see the graphs here.
The bottom line is that while constant run time graphs for alkaline cells might accurately represent performance of lights that are run continuously, they don't give a good picture of what you can expect from a more occasionally used light. An alkaline battery can often be a practical supply for a light used for short periods at a time, even if the current draw is high.
c_c
Alkaline cells, however, don't. They deliver a lot more total energy at low currents than they do at high currents, and a lot more if discharged in small doses with a rest in between.
So you can often get a much longer total run time from an alkaline cell powered light if you use the light only for short periods of time with a rest between, than you can if you just turn it on until the battery goes dead. Most of the run time graphs show only the latter case, which might not be the way you typically use your light, so you can easily get a pessimistic view of the amount of total run time you could get in practice.
I recently recorded some run times for a Kai Domain "Buckle Light", which draws a very heavy current from its AAA cell supply. Not surprisingly, it doesn't last long at all when run from an alkaline cell -- at least not if the light is kept on constantly. But after running the light until the light output was very low, I turned it off and let it sit for about 18 hours. Then I turned it on again with the same alkaline cell still in the light. The result was quite a bit more run time at a lower but still very usable light level. About 24 hours after that, I did it again, and got several minutes more. Although you can get even more by using the light for short periods of time with rests between, this test shows the ability of an alkaline cell to recover somewhat after even running the battery nearly completely down. You can see the graphs here.
The bottom line is that while constant run time graphs for alkaline cells might accurately represent performance of lights that are run continuously, they don't give a good picture of what you can expect from a more occasionally used light. An alkaline battery can often be a practical supply for a light used for short periods at a time, even if the current draw is high.
c_c
