I have an impression that the information about ZebraLight H501s runtime behavior posted in the "Some ZebraLight H501 runtime graphs" thread is getting too fragmented and hard to read. It may be a good idea to gather everything in one place. I hope it is ok to start a new thread on the topic...
In this post the results of the runtime tests of ZebraLight H501 and H501w lights are discussed. The tests were conducted last week to see how the lights behave in different modes and with different battery types. I ran full runtime tests for the high and medium mode and for NiMh and LiIon batteries. In the low mode only a short brightness output level test was performed.
In the first section of the post the test setup is described. The second section shows the relative comparison of the lights brightness for different modes and battery chemistries. The next two sections discuss the high and medium mode tests results for NiMH and LiIon batteries. In the fifth section a brief comparison of the lights current and power consumption is given. The section six shows selected detailed graphs of the circuit regulation behavior. The final section provides preliminary conclusions drawn from the performed tests.
I don't have a luxmeter so for my test I used a DMM measuring the short circuit current on a Vishay Semiconductors BPW21R photodiode. The diode has a built in correction filter to give an approximation of the spectral response of the human eye. Between 10^-2 and 10^5 lux it has a linear relation between the photocurrent and the illumination. The current is also largely independent of the temperature. The diode was put inside a 30mm long, 12mm wide white PVC pipe with an aluminum foil cylinder inside to reflect the light. The H501 was placed on the other side of the pipe.
The measurement results were recorded with the frequency of 5 data points approximately every 2 seconds (i.e. ~2.5 datapoint per second).
I believe this setup let me perform meaningful measurements. I cannot use it to determine the precise lux or lumen values (has anyone already checked them for H501?) but the relative values described below should be accurate.
In the NiMH tests I used Sanyo 2700 mAh NiMH batteries. I usually use Eneloops but this is the same battery ZebraLight used in their specifications. The batteries were charged on the Maha C-9000 and removed after the charger reported that charging is "done" (so there was no top off charging performed). My batteries measure only around 2500mAh on the Maha C-9000. The batteries were left to settle down for one or two hours before the usage.
In the LiIon tests the "Blue" TrustFire 14500 batteries (DX sku.3435) were used. They are rated 900mAh but I believe they are substantially less - I think around 700mAh. The LiIon batteries were charged with UltraFire WF-139 charger They were removed after the green diode indicated charging is complete and left for one or two hours to settle down.
When comparing NiMH and LiIon runtimes it's important to remember that the mAh "capacity" numbers are not directly comparable between different chemistries. A NiMH cell nominal voltage is 1.2V while for a LiIon cell it is 3.7V. Ideally it would be best to know how many Wh a battery under particular load holds. I don't know that. A close approximation is that for a Sanyo NiMh cell the number is 3Wh (~1.2V * 2.5Ah). If the TrustFire LiIon cell would really be 900mAh, it would hold approximately 3.3 Wh (~3.7V * 0.9Ah). I think in reality a TrustFire battery is probably closer to 650-750mAh so around 2.5Wh. It means that it probably holds around 10%-20% less energy than my Sanyo 2700 NiMHs.
To compare relative brightness for different modes and different battery chemistries I ran a short test. The lights were turned on for 10 minutes in every mode and then the test was interrupted.
In this test the obtained values depend on the exact placement of the light head so the graph shows only an approximate relation. Nevertheless the results well approximate the lumen outputs given in the lights descriptions.
In this graph the 100% value represents the illumination given by the H501 in the high mode with a NiMH battery.
Fig. 1 H501 and H501w output comparison
The low level outputs for the H501 on a LiIon battery and for H501w on a NiMH battery are too close (2.72% and 2.69% respectively) to be distinguishable on this plot.
In this test the obtained values depend on the exact placement of the light head so the graph shows only an approximate relation. Nevertheless for NiMH batteries the results well approximate the lumen outputs given in the lights descriptions.
Note that in the high mode with a LiIon battery the H501 offers only ~40% of the NiMH output. In the high mode the H501w is also around 10% dimmer than H501 (not really a noticeable difference). In the medium and low modes the differences between both lights and both chemistries are completely invisible.
Two full length tests were performed for NiMH batteries. When the light approaches the end of a NiMH battery capacity it starts to flicker. When the flickering starts it is fast but delicate and almost invisible. After a while it starts to be more and more visible and annoying. I think it is not a built-in functionality but only a side effect of the way the circuit works. The flickering isn't present when LiIon batteries are used. When present the flickering can be used as an indicator that the battery starts to run out.
In the high mode without cooling the light becomes uncomfortably hot. During this test the H501 was placed in a fridge. This was the only test not performed in room temperature.
Fig. 2 H501 NiMH high mode test
Please note that during the test the ambient temperature was 8 degrees centigrade. I think that in this temperature a NiMH battery can have lower (I guess between 5% and 15%) discharge capacity than in room temperature.
In the high mode the output is not strictly constant - it lowers slowly approaching 80% at the end of the runtime. I think this circuit behavior is the result of good design decisions. I like regulated lights but in the high mode I prefer them to give me, say, 2 hours of output with 80% light at the end than to give me constant 100% output at the cost of a much shorter runtime.
The medium mode test results were most important for me as I will be mainly using the lights in this mode. Chronologically this is also the first test that I performed.
Fig. 3 H501 NiMH medium mode test
The runtime achieved is shorter than 19 hours promised by ZebraLight but the batteries are only 2500mAh and were not topped off. If they really were 2700mAh, the light could indeed run for 19 hours (as was shown in other reports). In this mode the circuit keeps the output almost constant.
For LiIon batteries the high and medium runtime tests were also performed.
When LiIon battery is used in the high mode the output is lower and in room temperature the light doesn't noticeably heat.
Fig. 4 H501 LiIon high mode test
In the high mode with LiIons the output is around 40% of the NiMH output but with more than 2.5 times longer runtime (311 min vs. 115 min, i.e. 270%). The light is similarly regulated for both the chemistries but at the very end of the LiIon test the output jumps to 207% of the initial brightness. It lasts with the brightness above 180% for around 16 seconds and then turns itself off.
Fig. 5 H501 LiIon medium mode test
As you can see in the medium mode for Li-Ions the output is practically equal but the runtime is substantially lower than for NiMHs: 9 hours 41 minutes vs. 17 hours 18 minutes (i.e. only ~56%).
I have measured the initial current taken from a fresh battery while trying to understand why the H501 behaves differently for different chemistries.
The measured current explains why in the high mode LiIons when compared to NiMHs give ~40% output and ~270% runtime. I still don't understand though why in the medium mode the light has similar output but with only around half the runtime.
Two additional plots were prepared to show how the circuit fights to keep the light output constant. They are for a NiMH and a LiIon battery and both of them are for the medium mode. The plots are drown as a zoomed part of one of the respective graphs shown earlier.
For the NiMH test the zoomed part presents the measurement results from the first 1038 minutes (when the output was approximately constant). The output is indeed practically constant - a few percent difference between the highest and the lowest illumination is completely invisible to the eye. I wonder whether fluctuations like this are normal for all the circuits.
In the medium mode for LiIon batteries the output doesn't "jump" in the way similar to the medium mode for NiMHs. It gradually lowers from 100% to 96% few minutest before the end of runtime. Then it starts to act interestingly, as shown in the plot above.
The measured NiMH runtimes are close to the ones specified by ZebraLight. In my tests they were slightly shorter than what is advertised but I believe that the capacity of my Sanyo 2700 batteries (measured 2500mAh instead of 2700mAh) are on the lower end of the spectrum.
The high and medium modes are nicely regulated. The output for both the chemistries (NiMH and LiIon) is practically constant for the medium mode and gradually dims to 80% at the end for the high mode.
The lights behave differently for different battery types. In the high mode LiIons offer less than half the output than NiMHs (~40%) but also more than 2.5 times the runtime (~270%). In this mode with a LiIon battery the light also doesn't heat up. I think this setup may sometimes be useful when twice the medium mode brightness is needed but for longer than NiMH high mode runtime.
In the medium mode for LiIon batteries the light seems to be really inefficient giving the same output as for NiMHs but only approximately half the runtime.
When a NiMH battery is used the light starts to flicker at the end of the runtime. This behavior is not present for LiIon cells.
Introduction
In this post the results of the runtime tests of ZebraLight H501 and H501w lights are discussed. The tests were conducted last week to see how the lights behave in different modes and with different battery types. I ran full runtime tests for the high and medium mode and for NiMh and LiIon batteries. In the low mode only a short brightness output level test was performed.
In the first section of the post the test setup is described. The second section shows the relative comparison of the lights brightness for different modes and battery chemistries. The next two sections discuss the high and medium mode tests results for NiMH and LiIon batteries. In the fifth section a brief comparison of the lights current and power consumption is given. The section six shows selected detailed graphs of the circuit regulation behavior. The final section provides preliminary conclusions drawn from the performed tests.
1. Test Setup
I don't have a luxmeter so for my test I used a DMM measuring the short circuit current on a Vishay Semiconductors BPW21R photodiode. The diode has a built in correction filter to give an approximation of the spectral response of the human eye. Between 10^-2 and 10^5 lux it has a linear relation between the photocurrent and the illumination. The current is also largely independent of the temperature. The diode was put inside a 30mm long, 12mm wide white PVC pipe with an aluminum foil cylinder inside to reflect the light. The H501 was placed on the other side of the pipe.
The measurement results were recorded with the frequency of 5 data points approximately every 2 seconds (i.e. ~2.5 datapoint per second).
I believe this setup let me perform meaningful measurements. I cannot use it to determine the precise lux or lumen values (has anyone already checked them for H501?) but the relative values described below should be accurate.
In the NiMH tests I used Sanyo 2700 mAh NiMH batteries. I usually use Eneloops but this is the same battery ZebraLight used in their specifications. The batteries were charged on the Maha C-9000 and removed after the charger reported that charging is "done" (so there was no top off charging performed). My batteries measure only around 2500mAh on the Maha C-9000. The batteries were left to settle down for one or two hours before the usage.
In the LiIon tests the "Blue" TrustFire 14500 batteries (DX sku.3435) were used. They are rated 900mAh but I believe they are substantially less - I think around 700mAh. The LiIon batteries were charged with UltraFire WF-139 charger They were removed after the green diode indicated charging is complete and left for one or two hours to settle down.
When comparing NiMH and LiIon runtimes it's important to remember that the mAh "capacity" numbers are not directly comparable between different chemistries. A NiMH cell nominal voltage is 1.2V while for a LiIon cell it is 3.7V. Ideally it would be best to know how many Wh a battery under particular load holds. I don't know that. A close approximation is that for a Sanyo NiMh cell the number is 3Wh (~1.2V * 2.5Ah). If the TrustFire LiIon cell would really be 900mAh, it would hold approximately 3.3 Wh (~3.7V * 0.9Ah). I think in reality a TrustFire battery is probably closer to 650-750mAh so around 2.5Wh. It means that it probably holds around 10%-20% less energy than my Sanyo 2700 NiMHs.
2. Output comparison
To compare relative brightness for different modes and different battery chemistries I ran a short test. The lights were turned on for 10 minutes in every mode and then the test was interrupted.
In this test the obtained values depend on the exact placement of the light head so the graph shows only an approximate relation. Nevertheless the results well approximate the lumen outputs given in the lights descriptions.
In this graph the 100% value represents the illumination given by the H501 in the high mode with a NiMH battery.
Fig. 1 H501 and H501w output comparison
The low level outputs for the H501 on a LiIon battery and for H501w on a NiMH battery are too close (2.72% and 2.69% respectively) to be distinguishable on this plot.
In this test the obtained values depend on the exact placement of the light head so the graph shows only an approximate relation. Nevertheless for NiMH batteries the results well approximate the lumen outputs given in the lights descriptions.
Note that in the high mode with a LiIon battery the H501 offers only ~40% of the NiMH output. In the high mode the H501w is also around 10% dimmer than H501 (not really a noticeable difference). In the medium and low modes the differences between both lights and both chemistries are completely invisible.
3. NiMH batteries
Two full length tests were performed for NiMH batteries. When the light approaches the end of a NiMH battery capacity it starts to flicker. When the flickering starts it is fast but delicate and almost invisible. After a while it starts to be more and more visible and annoying. I think it is not a built-in functionality but only a side effect of the way the circuit works. The flickering isn't present when LiIon batteries are used. When present the flickering can be used as an indicator that the battery starts to run out.
In the high mode without cooling the light becomes uncomfortably hot. During this test the H501 was placed in a fridge. This was the only test not performed in room temperature.
Fig. 2 H501 NiMH high mode test
Please note that during the test the ambient temperature was 8 degrees centigrade. I think that in this temperature a NiMH battery can have lower (I guess between 5% and 15%) discharge capacity than in room temperature.
In the high mode the output is not strictly constant - it lowers slowly approaching 80% at the end of the runtime. I think this circuit behavior is the result of good design decisions. I like regulated lights but in the high mode I prefer them to give me, say, 2 hours of output with 80% light at the end than to give me constant 100% output at the cost of a much shorter runtime.
The medium mode test results were most important for me as I will be mainly using the lights in this mode. Chronologically this is also the first test that I performed.
Fig. 3 H501 NiMH medium mode test
The runtime achieved is shorter than 19 hours promised by ZebraLight but the batteries are only 2500mAh and were not topped off. If they really were 2700mAh, the light could indeed run for 19 hours (as was shown in other reports). In this mode the circuit keeps the output almost constant.
4. LiIon batteries
For LiIon batteries the high and medium runtime tests were also performed.
When LiIon battery is used in the high mode the output is lower and in room temperature the light doesn't noticeably heat.
Fig. 4 H501 LiIon high mode test
In the high mode with LiIons the output is around 40% of the NiMH output but with more than 2.5 times longer runtime (311 min vs. 115 min, i.e. 270%). The light is similarly regulated for both the chemistries but at the very end of the LiIon test the output jumps to 207% of the initial brightness. It lasts with the brightness above 180% for around 16 seconds and then turns itself off.
Fig. 5 H501 LiIon medium mode test
As you can see in the medium mode for Li-Ions the output is practically equal but the runtime is substantially lower than for NiMHs: 9 hours 41 minutes vs. 17 hours 18 minutes (i.e. only ~56%).
5. Current and power consumption
I have measured the initial current taken from a fresh battery while trying to understand why the H501 behaves differently for different chemistries.
Code:
NiMH LiIon
Current [mA] ~Power [mW] Current [mA] ~Power [mW]
High 1150 1380 134 495.8
Med 160 192 71.9 266.03
Low 35.5 42.6 14.5 53.65Table 1 H501 current and power consumption
The measured current explains why in the high mode LiIons when compared to NiMHs give ~40% output and ~270% runtime. I still don't understand though why in the medium mode the light has similar output but with only around half the runtime.
6. Additional plots
Two additional plots were prepared to show how the circuit fights to keep the light output constant. They are for a NiMH and a LiIon battery and both of them are for the medium mode. The plots are drown as a zoomed part of one of the respective graphs shown earlier.
Fig. 6 H501 NiMH medium mode test (zoomed)
For the NiMH test the zoomed part presents the measurement results from the first 1038 minutes (when the output was approximately constant). The output is indeed practically constant - a few percent difference between the highest and the lowest illumination is completely invisible to the eye. I wonder whether fluctuations like this are normal for all the circuits.
Fig. 7 H501 LiIon medium mode test (zoomed)
In the medium mode for LiIon batteries the output doesn't "jump" in the way similar to the medium mode for NiMHs. It gradually lowers from 100% to 96% few minutest before the end of runtime. Then it starts to act interestingly, as shown in the plot above.
7. Conclusions
The measured NiMH runtimes are close to the ones specified by ZebraLight. In my tests they were slightly shorter than what is advertised but I believe that the capacity of my Sanyo 2700 batteries (measured 2500mAh instead of 2700mAh) are on the lower end of the spectrum.
The high and medium modes are nicely regulated. The output for both the chemistries (NiMH and LiIon) is practically constant for the medium mode and gradually dims to 80% at the end for the high mode.
The lights behave differently for different battery types. In the high mode LiIons offer less than half the output than NiMHs (~40%) but also more than 2.5 times the runtime (~270%). In this mode with a LiIon battery the light also doesn't heat up. I think this setup may sometimes be useful when twice the medium mode brightness is needed but for longer than NiMH high mode runtime.
In the medium mode for LiIon batteries the light seems to be really inefficient giving the same output as for NiMHs but only approximately half the runtime.
When a NiMH battery is used the light starts to flicker at the end of the runtime. This behavior is not present for LiIon cells.
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