Hello everyone:
I've been interested in flashlights for quite some time. However, I have only recently been rather badly bitten by an actual flashlight bug.
If I were to blame one light for causing my current troubles, it would probably have to be the Fenix PD32UE . . . it has a combination of features that I found very intriguing (and had wanted to have for quite some time). I knew that my current stock of 18650's would probably not be up to the demands of this light. They are all getting at least a couple years old, most of them are - admittedly - of the bargain variety, and they spent most of their standby time in pretty much a full charge state.
I initially acquired a couple of 3100 mAhr Panasonics and they certainly do work OK. But, due to the bite from the bug, I have also been looking at some other lights and consequently also wound up looking into lithium ion batteries a little more carefully. Thanks to the valuable information that can be found on this forum, I discovered - surprisingly, to me - that the Sanyo "UR18650FM" might actually provide better performance with a light like the PD32UE, even with its capacity rating of a "mere" 2600 mAhr. It maintains a flatter or more stable voltage curve during discharge, meaning that it would probably be able to better maintain close to full output for a greater portion of a cell's discharge cycle. Having learned this, I ordered a couple of these cells and just recently received them.
Although I do not have a lot of instrumentation available, I do have a simple light meter and it occurred to me last night that I could get an actual measure of relative performance for these two 18650 options. The observations I am reporting here are based on only one run with a Panasonic NCR18650A (3100 mAhr) and a Sanyo UR18650FM (2600 mAhr), so I wouldn't take the actual numbers as too concrete. But even with the data being pretty limited, they do make enough of a point to make the observation worth passing on.
I do have a "hobby charger" and the cells used here have been very recently analyzed from rested full charge to a 3.0 volt cutoff at 1.8 and 2.8 amp rates, both right after receipt and after a few shallow to modest cycles of general use and fooling around. mAhr values were consistent with what one would expect based on those reported in HKJ's battery tests, so I'm pretty confident that the data here, though limited, are not skewed by the unknowing use of a cell with atypically bad or good performance.
I should note, however, that the measurements made with the PD32UE were collected with the cells starting at 4.04 volts. With my acquisition of new (and good quality!) cells, I had decided that they would generally be kept at a bit of an undercharge when in standby. Since the idea of this experiment came to me rather suddenly, I just used them the way they were.
I set the light up to measure relative output by "ceiling bounce". This was done in a spare bedroom that is very cool (North Dakota winter here), so heating was not found to be significant over the course of the run. Since the maximum ("burst") output of the PD32UE cannot be maintained continuously, I decided that I would run a series of 10 minute discharge sequences - each including 30 seconds of burst (reported by Fenix to be 740 lumens), followed by 9.5 minute on turbo (400 lumens). In each case, burst output was recorded at the end of the 30 second burst operation. Although this selected discharge pattern was essentially arbitrary, it is at least somewhat representative of how I might actually use the light in practice.
Like I said, the overall data here are limited, but sufficient to make the important point:
After an hour (that is, six total burst/turbo sequences), the Panasonic NCR18650A was providing a burst output that was about 84% of its initial value (this would actually be as measured at the end of the seventh 30 second run in "burst" output). When I get a chance to collect some more data, I will look into putting things in a graphical form, but I'll just note for the moment that the decline in burst output was pretty much continual, with each burst run being a little dimmer than the previous one. Output on the "turbo" setting stayed constant over the course of the runs with both the Sanyo and Panasonic cells.
With the Sanyo UR18650FM, initial burst output was about 5% higher than with the Panasonic, though this could conceivably be due to reproducibility problems with my setup. Either way, after the same 60 minutes and six full burst/turbo runs, the Sanyo still provided a burst output that was 95% of its initial value. I extended the Sanyo run out by another three cycles (out to 90 minutes, in other words). At that point, burst output was getting down to around 88% of initial. Also, it was now fading by several percent between the beginning and end of the tenth 30-second burst cycle, while in previous cycles it had held pretty constant over the course of each 30 second stint. In other words, the Sanyo was probably in the process of heading over the steeper voltage cliff that it shows at the end of a discharge.
Even though this quick experiment was pretty slapdash, it quite clearly shows that the lower capacity, but flatter voltage Sanyo cell will provide markedly better performance in an application like this. However, this assumes that "performance" is defined as maintaining maximum burst-setting lumen output for as much of the battery cycle as possible. In some situations - anything from a camping trip to an emergency - longer total runtime may be far more important than stable output. In such cases, the higher capacity option may be the better choice. This is especially true since the dropping voltage of a cell like the Panasonic will actually cause the light to use less power (when on the higher settings, anyways) as the discharge continues. All of this assumes, as is the case with the PD32UE, that one is talking about a light that runs on one 18650 and that does not use any "boost" type circuitry.
I found this little experiment to be rather fun as well as informative. Chronic flashaholics would probably warn that this is a bad sign. Either way, I will make some more measurements in a little more of a legitimately "scientific" fashion (and then figure out how to insert a graphical representation of the data into a post). In addition to repeating the same basic measurements, I should also try it starting with fully charged cells, of course. Also (duh!), I should collect a true reference measurement for FULL burst output by measuring it with the light powered by a pair of fresh 123A's. However, it might be a few days before I get to any further efforts. As such, I thought it appropriate to report these initial results because I know that there are at least a few folks who are wondering about appropriate battery choices for the PD32UE and other similar lights.
Thanks much to the folks on CPF who have posted the amazing amounts of useful data and information, both on the operating details of various classes of lights and on the output details of different battery options!
Tim
I've been interested in flashlights for quite some time. However, I have only recently been rather badly bitten by an actual flashlight bug.
If I were to blame one light for causing my current troubles, it would probably have to be the Fenix PD32UE . . . it has a combination of features that I found very intriguing (and had wanted to have for quite some time). I knew that my current stock of 18650's would probably not be up to the demands of this light. They are all getting at least a couple years old, most of them are - admittedly - of the bargain variety, and they spent most of their standby time in pretty much a full charge state.
I initially acquired a couple of 3100 mAhr Panasonics and they certainly do work OK. But, due to the bite from the bug, I have also been looking at some other lights and consequently also wound up looking into lithium ion batteries a little more carefully. Thanks to the valuable information that can be found on this forum, I discovered - surprisingly, to me - that the Sanyo "UR18650FM" might actually provide better performance with a light like the PD32UE, even with its capacity rating of a "mere" 2600 mAhr. It maintains a flatter or more stable voltage curve during discharge, meaning that it would probably be able to better maintain close to full output for a greater portion of a cell's discharge cycle. Having learned this, I ordered a couple of these cells and just recently received them.
Although I do not have a lot of instrumentation available, I do have a simple light meter and it occurred to me last night that I could get an actual measure of relative performance for these two 18650 options. The observations I am reporting here are based on only one run with a Panasonic NCR18650A (3100 mAhr) and a Sanyo UR18650FM (2600 mAhr), so I wouldn't take the actual numbers as too concrete. But even with the data being pretty limited, they do make enough of a point to make the observation worth passing on.
I do have a "hobby charger" and the cells used here have been very recently analyzed from rested full charge to a 3.0 volt cutoff at 1.8 and 2.8 amp rates, both right after receipt and after a few shallow to modest cycles of general use and fooling around. mAhr values were consistent with what one would expect based on those reported in HKJ's battery tests, so I'm pretty confident that the data here, though limited, are not skewed by the unknowing use of a cell with atypically bad or good performance.
I should note, however, that the measurements made with the PD32UE were collected with the cells starting at 4.04 volts. With my acquisition of new (and good quality!) cells, I had decided that they would generally be kept at a bit of an undercharge when in standby. Since the idea of this experiment came to me rather suddenly, I just used them the way they were.
I set the light up to measure relative output by "ceiling bounce". This was done in a spare bedroom that is very cool (North Dakota winter here), so heating was not found to be significant over the course of the run. Since the maximum ("burst") output of the PD32UE cannot be maintained continuously, I decided that I would run a series of 10 minute discharge sequences - each including 30 seconds of burst (reported by Fenix to be 740 lumens), followed by 9.5 minute on turbo (400 lumens). In each case, burst output was recorded at the end of the 30 second burst operation. Although this selected discharge pattern was essentially arbitrary, it is at least somewhat representative of how I might actually use the light in practice.
Like I said, the overall data here are limited, but sufficient to make the important point:
After an hour (that is, six total burst/turbo sequences), the Panasonic NCR18650A was providing a burst output that was about 84% of its initial value (this would actually be as measured at the end of the seventh 30 second run in "burst" output). When I get a chance to collect some more data, I will look into putting things in a graphical form, but I'll just note for the moment that the decline in burst output was pretty much continual, with each burst run being a little dimmer than the previous one. Output on the "turbo" setting stayed constant over the course of the runs with both the Sanyo and Panasonic cells.
With the Sanyo UR18650FM, initial burst output was about 5% higher than with the Panasonic, though this could conceivably be due to reproducibility problems with my setup. Either way, after the same 60 minutes and six full burst/turbo runs, the Sanyo still provided a burst output that was 95% of its initial value. I extended the Sanyo run out by another three cycles (out to 90 minutes, in other words). At that point, burst output was getting down to around 88% of initial. Also, it was now fading by several percent between the beginning and end of the tenth 30-second burst cycle, while in previous cycles it had held pretty constant over the course of each 30 second stint. In other words, the Sanyo was probably in the process of heading over the steeper voltage cliff that it shows at the end of a discharge.
Even though this quick experiment was pretty slapdash, it quite clearly shows that the lower capacity, but flatter voltage Sanyo cell will provide markedly better performance in an application like this. However, this assumes that "performance" is defined as maintaining maximum burst-setting lumen output for as much of the battery cycle as possible. In some situations - anything from a camping trip to an emergency - longer total runtime may be far more important than stable output. In such cases, the higher capacity option may be the better choice. This is especially true since the dropping voltage of a cell like the Panasonic will actually cause the light to use less power (when on the higher settings, anyways) as the discharge continues. All of this assumes, as is the case with the PD32UE, that one is talking about a light that runs on one 18650 and that does not use any "boost" type circuitry.
I found this little experiment to be rather fun as well as informative. Chronic flashaholics would probably warn that this is a bad sign. Either way, I will make some more measurements in a little more of a legitimately "scientific" fashion (and then figure out how to insert a graphical representation of the data into a post). In addition to repeating the same basic measurements, I should also try it starting with fully charged cells, of course. Also (duh!), I should collect a true reference measurement for FULL burst output by measuring it with the light powered by a pair of fresh 123A's. However, it might be a few days before I get to any further efforts. As such, I thought it appropriate to report these initial results because I know that there are at least a few folks who are wondering about appropriate battery choices for the PD32UE and other similar lights.
Thanks much to the folks on CPF who have posted the amazing amounts of useful data and information, both on the operating details of various classes of lights and on the output details of different battery options!
Tim