Many people mention that the new SSC P7 lights get very hot very quickly, so I've decided to take some (quite unscientific though) measurements. Your comments are welcome, especially regarding measurement methodology.
Light: MTE SSC P7 5-mode (sku.12060), laid horizontally flat on the table, switched on in high mode (the first one).
Battery: protected Trustfire 18650 (sku.5776), freshly charged using Trustfire charger (sku.4151).
Voltage: initial 4.1V, final 3.92V (battery).
Current: initial 2.6A, final 1.32A (tailcap). (previous invalid measurement was 1.5A)
Room (ambient) temperature: ~26C.
Temperature was measured from the side, at four points: 1) bezel, 2) fins at the end of the head, 3) middle (knurled part), 4) tailcap. Readings were started in intervals shown below, then it took ~15s to complete each cycle of all 4 readings (so the tail reading is actually at N+15s).
After 10 minutes the light was very hot and unpleasant to touch. I switched it off, disassembled to cool down and measured two additional temperatures:
Battery temperature: 50C (after 10 minutes)
Inside compartment: 58C (after 10 minutes)
For comparison my laptop is 36..42C on idle (mail/web), up to 46..50C (max CPU).
Comments:
- battery got very hot. What is safe temperature limit for Li-Ion 18650?
- temperature gradient seems to be ~3C/minute in the first 5 minutes, then gradually drops to ~2C/minute for the second period. This means that excess heat is either radiated out or builds in some other area inside the light, probably it is absorbed by the battery.
- head was slightly unscrewed (1 full turn) because when it is fully tightened there is a dark spot in the middle of the beam that I don't like (whitewall effect only
). When the head is fully screwed on, heat transfer works slightly different and the fins were the hottest point (not middle body).- measurements were done in "worst case" = stationary position of the light. When I held the light in hand, excess heat was transferred to human body. It was more difficult to measure temperatures correctly in such a setup (not enough hand to hold light, make measurements and write them down ), but they were lower, between 47..50C (instead of >55C). If you use the light in real life (walking, biking), it's temperature should probably be bearable.
- voltage measured at the open tailcap is 0.8V lower than at battery. I'm not sure how to interpret it, except that this drop is on driver.
About measurement tools:
- I have checked again with a proper meter and the LED gets 2.6A current with fresh battery. This corresponds correctly to Vf ~3.4V measured at the LED and to SSC P7 theoretical characteristic. Cheap (10$ at supermarket) multimeter that I've used previously showed only 1.5A, which was not a correct reading.
- pyrometer might not give an accurate absolute temperature, due to the way all such devices work (measuring radiated heat). I don't have other device to verify the readings, but those should be good enough to show trends and relative changes. Emmisivity was set to 0.95.
Light: MTE SSC P7 5-mode (sku.12060), laid horizontally flat on the table, switched on in high mode (the first one).
Battery: protected Trustfire 18650 (sku.5776), freshly charged using Trustfire charger (sku.4151).
Voltage: initial 4.1V, final 3.92V (battery).
Current: initial 2.6A, final 1.32A (tailcap). (previous invalid measurement was 1.5A)
Room (ambient) temperature: ~26C.
Temperature was measured from the side, at four points: 1) bezel, 2) fins at the end of the head, 3) middle (knurled part), 4) tailcap. Readings were started in intervals shown below, then it took ~15s to complete each cycle of all 4 readings (so the tail reading is actually at N+15s).
Code:
time bezel fins middle tail
[min] [C] [C] [C] [C]
0 26.8 26.8 26.8 26.8
0.5 27.3 29.2 28.6 27.8
1 28.5 29.5 30.4 29.2
1.5 30.4 31.5 33.8 31.7
2 32.0 33.3 35.5 33.1
2.5 33.6 34.8 36.8 34.4
3 35.1 36.0 38.3 36.1
4 38.0 39.2 41.5 39.0
5 40.9 42.0 45.0 42.3
6 43.1 44.5 47.3 44.3
7 45.4 46.8 49.7 46.9
8 46.8 48.5 52.1 48.8
9 49.1 50.7 53.9 50.5
10 49.5 52.3 55.6 52.4Battery temperature: 50C (after 10 minutes)
Inside compartment: 58C (after 10 minutes)
For comparison my laptop is 36..42C on idle (mail/web), up to 46..50C (max CPU).
Comments:
- battery got very hot. What is safe temperature limit for Li-Ion 18650?
- temperature gradient seems to be ~3C/minute in the first 5 minutes, then gradually drops to ~2C/minute for the second period. This means that excess heat is either radiated out or builds in some other area inside the light, probably it is absorbed by the battery.
- head was slightly unscrewed (1 full turn) because when it is fully tightened there is a dark spot in the middle of the beam that I don't like (whitewall effect only
). When the head is fully screwed on, heat transfer works slightly different and the fins were the hottest point (not middle body).- measurements were done in "worst case" = stationary position of the light. When I held the light in hand, excess heat was transferred to human body. It was more difficult to measure temperatures correctly in such a setup (not enough hand to hold light, make measurements and write them down ), but they were lower, between 47..50C (instead of >55C). If you use the light in real life (walking, biking), it's temperature should probably be bearable.- voltage measured at the open tailcap is 0.8V lower than at battery. I'm not sure how to interpret it, except that this drop is on driver.
About measurement tools:
- I have checked again with a proper meter and the LED gets 2.6A current with fresh battery. This corresponds correctly to Vf ~3.4V measured at the LED and to SSC P7 theoretical characteristic. Cheap (10$ at supermarket) multimeter that I've used previously showed only 1.5A, which was not a correct reading.
- pyrometer might not give an accurate absolute temperature, due to the way all such devices work (measuring radiated heat). I don't have other device to verify the readings, but those should be good enough to show trends and relative changes. Emmisivity was set to 0.95.
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