To expand on this:
The cell is rated for 15A current draw. In theory, it can provide roughly 15A from full to empty without overheating. In practice, refer to HKJâs tests.
What a light will actually draw from a cell depends. With âdirect driveâ, the actual power output is an intersection of the batteryâs voltage vs. current curve and the voltage vs. current curve from the flashlightâs entire system (LED, driver, springs, contact resistances, etc.). So if you put a higher forward-voltage LED in a flashlight (XM-L2, for example) and a FET driver, you wonât get a ton of current. If you put the lowest Vf LED you can find, like a Luxon V or White Flat 2mm^2, and a very good battery, you could risk burning out the emitter from pulling too many amps! And if you put a bad battery, it would be risky because you could exceed the batteryâs rating and/or where itâs been tested to perform safely (not always the same thing).
I think this has been answered, but I will go into more detail on battery ratings.
All batteries should have factory ratings. Besides continuous discharge there are charge rates for battery life, charge rates with reduced life, operating temperatures, storage temperatures and on and on. Itâs pretty interesting to read factory battery specifications. I keep a lot of them in PDF form on my phone for quick reference. Here is the 30Q link.
The 15A 30Q rating is max continuous output without the cell going over its max rated surface temperature. Typical battery temperature upper limits are 60°C to 85°C. (High capacity cells tend to be on the lower side of this temp range and high drain cells tend to be on the higher temp side, generally speaking) The 30Q is in the middle at 75°C. These load tests take a lot of time to perform and really stress the cell so they are usually done in increments of 5A. HKJ and Mooch will test and record the output and temperature curve.
In HKJâs test the 30Q made it from 4.2v to 2.8v without exceeding the 75°C temperature limit (71°C). It made it down to 3.15v at 20A before he stopped the test due to its temperature reaching 75°C.
Mooch tested the cell all the way down to 2.8v at 20A and 25A. His 15A test also recorded a temperature of 71°C. At 20A it got to 83°C and 25A got to 96°C. So it survived, didnât burst in flames or anything, just got really hot. It can do these higher amps, but itâs not recommended as eventually it damages the cell and can be dangerous.
So you see there are a lot of variables in testing. We could probably say the 30Q should be rated at 16A as it would still stay under 75°C. 15A is good enough.
Some rewrap companies may list a 30Q with a max continuous current of 25A, because it really can do 25A, but they will put âup to 75°Câ in the fine print. Some folks miss the fine print or maybe donât understand it and just assume this is a better battery. You have to watch out for companies doing this. Find out what cell is under the wrapper and then find the specs for that cell.
A 30Q might even be able to do 40A for 5 seconds or something like that. Shorter durations can allow higher amps. Sometimes the factory will give these rating for 5, 10, 20 or 30 second bursts. I canât remember what cells I saw these specs in, but they were factory specs.
I see it the other way, any man can be a daddy but it takes a man to be a father. A âfather figureâ is responsible for raising and providing care and safety for a child, a âdaddyâ is just responsible for getting someone pregnant.
Thanks for the explanation Scallywag! Sadly I still donât understand most of what you said as Iâm having a hard time understanding the engineering side of what goes on here. Hopefully soon I can. But I still got the answer to my question regardless! :partying_face:
Just because a flashlight uses a FET driver does not mean itâs like running a wire from the positive to the negative of the battery. This might produce 100+ amps! The led acts like a resistive load. The springs, FET model, led wires, body threads, etc⌠all create resistance.
With a particular battery, if you increase the resistance, the amperage goes down. If you decrease resistance the amperage goes up.
FET drivers can only be used with certain LEDs. Even then, you may be limited to certain batteries. It is a balancing act.
Candlepower is an old measurement not used any more.
Candela is about intensity or how light is spread out/concentrated. This is how we measure throw distance.
Lumens are about the total light that is scattering in all directions.
Youâve seen zoomy lights, right? It can change the angle of the beam. Changing the beam angle to be more narrow creates higher intensity or candela even though the led is still putting out the same lumens. So candela changes but lumens donât.
(Note that zoomy lights are a tricky example to use because their optical efficiency changes a lot as the lens focus changes. The lumens going out the front does drop off a lot as you narrow the beam angle even though the led lumens donât change)
To give another example, I had two lights with the same reflector size. One with a 70.2 and one with a 50.2 led. In order to get the same intensity, or brightness in the hot spot, I found the 70.2 light needed 1000 lumen while the 50.2 light only needed 600 lumen. So two different lumen levels, but the same intensity due to the different size of the hot spots.
love the alien conversation. my .2 cents is that there are lots and lots of civilisations out there and wouldnât it be cool if we managed to not kill ourselves long enough to meet one.
now a stupid light question.
say I had a JETBeam WL-S4-GT with a XHP 70 led, and I really really like it, donât want to mess it up, and donât have mod experience.
then I see that XHP 70.2 comes out and think, it would be cool to put that in. is it an easy switch? will I mess my light up? is XHP 70.2 much better? (according to a random youtube video it could be).
The 70.2 at about 5 amp (I think thatâs about the level the WL-S4-GT uses) will probably add a few hundred lumen on max. Not enough to really notice with your eyes. What you will see is the tint difference. The 70.2 is a flip chip design and it creates a yellow Corona around the hot spot. A lot of people prefer the older 70 for itâs nicer tint.
The real advantage of the 70.2 comes when you push it hard, at say 15-20 amps. Then it leaves the 70 in the dust, as it maxes out at about 12 amp.
Another advantage of the 70.2 is it has a smoother hot spot with only a faint dark center. The 70 has a noticable dark center (when used with SMO reflector). Your light uses a orange peel reflector so you wonât see much difference there.
I would not bother swapping it out. If you wanted to try, itâs as easy as ordering a new led on a similar size mcpcb and swapping it. Iâm guessing itâs a 6v unit. Verify that before ordering. Then you just solder the 2 led wires. Pretty easy.
Is it possible to use SST20, LH351D and Nichia 219C together in a direct drive setup for tint mixing? Would they differ much in brightness or burn due to different forward voltages?
Yes, that is what I supposed. I wanted to try the SST20 and 219C 5000K together to increase rosiness and get a 4500K tint. They would get around 3 - 5A per led. Do you think the 219C would draw more current than is good for it?
So I might need to mix LH351D and SST20, throwy in the center and floody outside, not bad either.