52°C is not a problem. It actually improves performance, especially in the cold.
Not good test conditions, the problem is obviously going to be more evident when the light is standing on a non thermally conductive surface, not lying on its side generating a convection current past the hot spot with cool air.
Below are my temperature measurements, using a fully charged Samsung 30Q cell. I ran the test for 60 minutes, measuring every 10 minutes with an IR thermometer. The measurement is the highest temperature observed on the base of the lantern, which was not actually the tail cap but a spot on the base just to the side of the tail cap, for some reason. Temperatures leveled off and started dropping from about 60 mins onward.
I ran the test twice:
(1) Base Temp 1 lantern position:
(2) Base Temp 2 lantern position:
The lantern was sitting on top of a speaker cabinet. Starting/ambient temp was 25 deg. C.
Thanks Pete, that looks like another well done & documented test… with decent results as far as the lantern goes.
Same goes for you JasonWW… well done with excellent documentation. :+1:
Sorry. Maybe I’ll do that the time time I’ve got a chance to measure again.
Maybe I’ll just let it run 40-50 minutes straight on a hard wood surface then measure the battery temp.
The most important thing is the battery temp, right?
Is it safe to assume the battery temp is always going to be a few degrees cooler than the tail cap temp? That’s what it seemed like on my tests.
So I’m guessing Petes batteries got up to 53°C or 54°C?
My battery temp did not exceed 50 deg C.
So your batteries ran at least five to six degrees cooler than your tail cap temperatures? Interesting.
Was the hottest part of the battery the negative base plate?
My T1 arrived today. Now fully-charged in the office, I will simulate the above 60-min test with my ir meter later tonight when I’m home.
Would you believe that the ‘Weather Station’ clock/thermometer/humidity/barometer is a product of Henry Xu of Opus?
Photo below shows the closeness of the ir’s reading to the Inside Temp of the Weather Station.
Later tonight I will start the 60min temp reading test…
Started the discharge test at 8:17 @ room temp of 26.8cel : (lantern standing on wood table during the duration of the test, except when taking temps)
After 17min., IR temp reading at 43.7c:
After 36min. : 52.3c
After 48min: 55.9c
After 1hr, 1min.: Temp started to decrease by 1.2degrees to 54.7c
After 1hr, 2min: Temp steadily decreasing to 53.1c
Removed cell while light is still on, cell temp 51.4c, Cell voltage: 3.66v
Definitely just fairly warm for electrical components standards, so it’s safe to use using even with the unknown OEM cell that came with it.
Well it appears, from Pete’s results, that the battery tube gets hotter when the light is upside down, which seems odd. This would seem to indicate that the heat concentrating at the tail cap is not due to that being the bottleneck of heat dissipation. If that were the case the light would cool more effectively upside down.
This makes me think that the outside diffuser is dissipating much more heat than it is given credit for, obviously it won’t appear as hot, as it has a much larger surface area. Maybe not such a bad design then, just slightly overpowered for its overall heat dissipation capability?
Just concluded a discharge temperature test on post 114. 
My bad. I must have measured cell temp incorrectly before. I re-ran the test (lantern in position 1), and after 60 minutes, lantern base was at 56 deg C, and cell temp was 56 deg C as well. This was the temp on lower half of the cell. The upper half was cooler.
Cell was at 3.83V at the time of measurement.
Thanks tatasal for posting your test results. Good info & well documented…. :+1: .
DBSAR, what kind of conclusions have you made about this temperature related issue on the T1?
In our own tests it seems most of the battery tubes never exceeded 60°C and the batteries themself seemed to range from 50°C to 56°C. (I haven’t had time to sort through all the posts)
You reported 67°C in your battery tube, right? Do you think your T1 was an anomaly or maybe we should test these lights in a hotter environment?
I looked at a few battery data sheets to see what kind of temperature related info I could find. It seems there is a regulation Per UL1642 that says cells have to withstand 130°C without exploding or burning. Edit: I see that the Panny B has an 80°C limit.
An operating range of up to 60°C surface temp seems to be the norm for most cells.
Do you think this means the T1 was built within the safety specs and your T1 had an issue? Even as hot as your battery tube got, your battery should not have been anywhere close to its danger limit.
Samsung 35E:
3.12 Operating Temperature (Cell Surface Temperature) Charge: 0 to 45°C - Discharge: –10 to 60°C
9.4 Heating Test
Test method: To heat the standard charged cell at heating rate of 5°C per minute up to 130°C and keep the cell in oven for 10 minutes. Criteria: No fire, and no explosion.
Sony VTC6:
2.6 Allowable Environment Temperature Charge 0～+60℃ -
Discharge –20～+60℃
2.8.2 Discharge Conditions
Discharge at cell surface temperature below 80℃.
I couldn’t see a max heating test.
LG MJ1:
2.9 Operating Temperature Charge 0 ~ 45℃ Discharge –20 ~ 60℃
4.5.4 Heating Test
Cells are charged per 4.1.1 and heated in a circulating air oven at a rate of 5ºC per minute to 130ºC. At 130ºC, oven is to remain for 10 minutes before test is discontinued (Per UL1642).
Specification: No explode, No fire
Samsung 30Q:
3.11 Operating temperature (surface temperature) Charge : 0 to 50℃ (recommended recharge release < 45℃) Discharge: –20 to 75℃
9.4 Heating test
Test method: To heat up the standard charged cell at heating rate 5℃ per minute up to 130℃ and keep the cell in oven for 10 minutes. Criteria: No fire, and no explosion.
Sanyo/Panasonic 3400B and 3500GA
5.12 Operating Temperature
Charge 0 ~ +40℃
Discharge –20 ~ +60℃
(2) High Temperature
“Do not use or place the battery near fire, a heater or a high temperatures (more than 80℃).”
The battery’s polyolefin separator may get damaged from the heat and could cause an internal short circuit. This may cause the battery to catch on fire, smoke, explode, or
cause heat generation.
It looks like Wimpy Water got removed from the forum (I wonder what he did). I wish he was here so he could apologize for accusing me of sweeping these temperature related issues under the carpet. He was way paranoid. :person_facepalming:
In this test venting is allowed, i.e. the cell is not usable after this.
The 60°C rating is not really maximum there is some safety included. This can be seen from some cells where the specifications allows up to maybe 80°C when using thermal cut-off.
The Wimp got wimped.
I don’t know what specific rule he broke, but it was obvious that he was more interested in trolling than content. He deliberately threw around insults and slipped provocative comments into his posts on a regular basis.
Ah, so venting is allowed. That makes sense. 130°C is pretty rediculous.
Yeah, 60°C is normal. They even store the cells at 60°C for a month to make sure they hold their charge.
What is interesting is the Sanyo/Panasonic data says the “polyolefin separator may get damaged” above 80°C. I wonder if this kind of separator is common among all the other brands of batteries as well. This might be considered the true temperature limit before venting. What do you think?