How durable can LEDs get before they're dangerous?

BeastFlashlight

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Last week i was reading that XML2 U3 can be driven harder then all former XMLs. Today i read that Cree's new XHPs could be driven much harder. It's so dangerous if the LEDs compete with the lithium batteries for the ability to handle amps. I had a high output flood light that fried the springs once, so i had it modded to a springless battery carrier...now i'm wondering if that was unwise. The springs may have been terrible and fragile i'm not sure, but i'm thinking that it's probably best to have a couple failure points prior to the lithium batteries exploding. Can u tell i just read my 1st thread about the dangers of lithium ion batteries?

Does anyone know how many amps decent springs shrivel up at? How about how many amps XML2 U3s fry at? I have 2 lights coming in (S200C2vn and TD15vn) and both require IMRs...i'm looking at the 20 amp ones and 35 amp ones and i was hoping someone can tell me how many amps fry spings and current LEDs. Of course the 35 amp ones have less capacity so that is a negative, 2500 mAh vs 3100 mAh
 

The Municipality

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The problem is springs need to be made of poor-conducting steel because it's really the only metal that can deform that much yet still return to its original shape - which is what allows it to keep constant pressure on the battery/driver/LED/etc. I'll tell you right now - 35amps is far too much current for a steel flashlight spring. To transfer that amount of current, copper is needed, but copper makes for such a terrible spring so the spring really just needs to be eliminated altogether. But this presents another problem - over-tightening your components.

I really don't see a conventional mass-produced flashlight in the works that will draw 35 amps. A steel spring would light up like a filament. And if solid contacts are used, people will over-tighten them and break the light - and no manufacturer wants to deal with ham-fisted n00b's trying to warranty something like that. A light like that is going to remain in the "custom" side of things - and it really should.
 

twl

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IMR is a safer chemistry, and much less likely to suffer problems like li-ion. If you plan on using high current lights, just use the IMRs. They don't have protection circuit boards, and don't really need any. But still observe safe battery practices anyway, as a regular habit.
 

BeastFlashlight

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IMR is a safer chemistry, and much less likely to suffer problems like li-ion. If you plan on using high current lights, just use the IMRs. They don't have protection circuit boards, and don't really need any. But still observe safe battery practices anyway, as a regular habit.

But i thought IMRs are lithium ion? Lol i don't know sh1t don't let my 1,000 posts fool anyone haha. I just ordered Efest IMRs!! So twl can u please throw out a few of the most important battery safety practices? I'm guessing they are to never prick or puncture them (and if so never use again), and never keep near high heat. Like i keep mine in the refrigerator for longer life is that ok?
 

onetrickpony

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When led's fry, there's not much damage to be done except that they will no longer work. Led's themselves will not explode or cause any collateral damage. If you pop a lithium ion battery, it can get dangerous.

If the led gets too hot for the solder that connects the wires they might detach, so I suppose that would be something to pay attention for if you think an led has died but in truth is just no longer connected to the circuit.

About springs, the best way I've found to overcome their limitations is the same as what most people modifying lights do which is to solder a copper wire (or use desoldering braid as I do) from the tailcap connection to the tip of the spring. You still get the aforementioned benefits of steel in that it can deform many thousands of times and apply sufficient pressure to the battery to maintain contact, while at the same time having the current handling capability of copper.

All that being said, high current lights ARE inherently more dangerous than their lower current brethren. Anything fun usually is.
 
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onetrickpony

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IMR's are lithium ion batteries, but they are a different chemistry with different properties (pros and cons for flashlight use). They typically have a lower capacity but are capable of much higher discharge currents than the batteries that you are probably used to. Check out this link: http://batteryuniversity.com/learn/article/types_of_lithium_ion

IMR's are the second one down on the chart, also known as LiMn2O4. The typical Lithium Ion you see at the top LiCoO2.

But i thought IMRs are lithium ion? Lol i don't know sh1t don't let my 1,000 posts fool anyone haha. I just ordered Efest IMRs!! So twl can u please throw out a few of the most important battery safety practices? I'm guessing they are to never prick or puncture them (and if so never use again), and never keep near high heat. Like i keep mine in the refrigerator for longer life is that ok?
 
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BeastFlashlight

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Nice link thanks. What's confusing me is that Vinh told me my light will be brighter with the 35A IMR than the 20A IMR because the 35A battery has a lower internal resistence, which means higher current thus stronger output. But I thought the amp rating on a battery simply means how much current it can safely handle before damage occurs?? A 35A battery CAUSES higher amps in the flashlight? I thought about it like a fuse that's rated higher, that it can simply HANDLE more heat...but the battery CAUSING more heat/current is confusing me.

...I thought the driver is what determined how much current drives the LED?? And the IMR batteries were needed for drivers that call for high current because they can handle higher currents (like a higher amp fuse handles more current). Somebody straighten me out please.

***Edit after getting home...i already owned a set of IMRs for 1 of my lights, wasn't sure what the max discharge was on those, i just checked and they are only 10A lol, now i'm really confused because these IMRs worked fine for me in my 'Direct drive' light which should have the highest current of all
 
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Closet_Flashaholic

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Presumably with the currents involved, we're probably dealing with a "high-end" light. So, that being said, silver plating the stainless steel springs might be an option. While silver would probably tarnish after a while, copper would be worse. IIRC I have several lights with gold-plated springs. Berylium copper might be an expensive option (also very toxic, but as long as one isn't putting it in one's mouth, should be okay)

Due to the skin-effect of current through conductors, the plating layer (gold, silver or copper) would carry the majority of the current at relatively low resistances and the stainless would still provide the mechanical strength to maintain the contact.

I think the bigger problem will be finding a power source will the right combination of cell counts and capacities that make monetary (and safety) sense. I don't see that right now: something that would deliver 35A at 3 volts, and certainly I can't think of a driver that would handle the current (and dissipate the heat) to provide a regulated output at those currents. I'm sure there's some electronics out there, but it won't be a pocket light, that's for sure.
 

onetrickpony

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I don't think that Vinh is incorrect, but I think what he said is a little unclear. Lower internal resistance will mean that more of the power the battery can produce is going to the led as opposed to producing heat in the battery. In addition, most drivers are somewhat voltage sensitive, in other words they do control current but not perfectly, and some operate basically direct drive in high mode. Lower internal resistance equals higher voltage under load.

The direct drive light you mentioned has resistances in it. The switch, battery contacts, wires, etc all contribute to resist the current the led can pull. Not to mention that the forward voltage of an led in a direct drive light will determine how much current it will pull. An led with a forward voltage of say 3.5v will be much much brighter using the same battery as an led with a forward voltage of 3.9.

Nice link thanks. What's confusing me is that Vinh told me my light will be brighter with the 35A IMR than the 20A IMR because the 35A battery has a lower internal resistence, which means higher current thus stronger output. But I thought the amp rating on a battery simply means how much current it can safely handle before damage occurs?? A 35A battery CAUSES higher amps in the flashlight? I thought about it like a fuse that's rated higher, that it can simply HANDLE more heat...but the battery CAUSING more heat/current is confusing me.

...I thought the driver is what determined how much current drives the LED?? And the IMR batteries were needed for drivers that call for high current because they can handle higher currents (like a higher amp fuse handles more current). Somebody straighten me out please.

***Edit after getting home...i already owned a set of IMRs for 1 of my lights, wasn't sure what the max discharge was on those, i just checked and they are only 10A lol, now i'm really confused because these IMRs worked fine for me in my 'Direct drive' light which should have the highest current of all
 

BeastFlashlight

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I don't think that Vinh is incorrect, but I think what he said is a little unclear. Lower internal resistance will mean that more of the power the battery can produce is going to the led as opposed to producing heat in the battery.


Hmm based on that why would anyone choose the 20A over the 35A IMR? (They're basically the same price)

Not to mention that the forward voltage of an led in a direct drive light will determine how much current it will pull. An led with a forward voltage of say 3.5v will be much much brighter using the same battery as an led with a forward voltage of 3.9.

I don't know what forward voltage of an LED means, is that an electronics semi conductor or something that's part of the LED that filters voltage? So the battery is 3.7V, so if the battery exceeds this forward voltage that's ok but if the battery falls short of it that is where output gets diluted? So if forward voltage was 3.5V and the battery was let's say 10V would that be ok too, would it perform just as good as with the 3.7V battery?
 

onetrickpony

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Hmm based on that why would anyone choose the 20A over the 35A IMR? (They're basically the same price)

I haven't looked at the specific batteries you're talking about but my guess would be capacity.

I don't know what forward voltage of an LED means, is that an electronics semi conductor or something that's part of the LED that filters voltage? So the battery is 3.7V, so if the battery exceeds this forward voltage that's ok but if the battery falls short of it that is where output gets diluted? So if forward voltage was 3.5V and the battery was let's say 10V would that be ok too, would it perform just as good as with the 3.7V battery?

The forward voltage of an led is the voltage at which the led pulls a given specified current. Here's part of a chart from the XML2 datasheet:

Forward voltage (@ 700 mA, 85 °C) V 2.85
Forward voltage (@ 1500 mA, 85 °C) V 3.05
Forward voltage (@ 3000 mA, 85 °C) V 3.3

The voltages shown are just what is typical or average, each led will be different, so if you get one that's on the low end of the spectrum it will be brighter at a lower voltage and vice versa.
 

BeastFlashlight

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Ok you are right because the 35As are 2500 mAh and the 20As are 3100 mAh. Wow do IMRs always give maximum lumen output compared to normal protected 18650s how about that (and higher still with higher amp IMRs). So i'm gonna use IMRs from now on even when they aren't needed. The 20A 3100 mAh Efests will be my happy medium.
 

onetrickpony

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Ok you are right because the 35As are 2500 mAh and the 20As are 3100 mAh. Wow do IMRs always give maximum lumen output compared to normal protected 18650s how about that (and higher still with higher amp IMRs). So i'm gonna use IMRs from now on even when they aren't needed. The 20A 3100 mAh Efests will be my happy medium.

There are situations where an IMR will not perform as well, like when you have a light that only pulls 700ma. The extra current capability of an IMR isn't needed, and a regular LiCo or whatever cell will hold its voltage just as well because it isn't being pushed. So you'd get a longer runtime. The IMR chemistry is still safer generally speaking, so it may be a wash depending on how you look at it.
 

twl

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Also, if you recharge regularly at moderate discharge levels to improve battery life, then the absolute max capacity of the battery may be of less importance because you aren't using the full capacity anyway.
I don't try to run batteries down till they shut off from the protection circuit.

With IMR, it may be helpful to have a light that does shut down at 3v or something like that, so that you be relatively sure that you won't over-deplete your unprotected battery.
Lights such as the Oveready Triple have such protection, and they are basically made to use IMR cells for the most part.
 

night.hoodie

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silver plating the stainless steel springs might be an option

I really wish we saw more Ag in all lights. Not just for contacts, but for reflectors, and surfuce of the host. I think its 20x the price of Cu by weight, and for its superior electrical/thermal conductive properties not necessarily worth it compared to Cu's likewise great properties, but the amount of Ag needed for plating a spring, contact, and even Sterling for the reflector (with coating to prevent or slow tarnish) should be negligible. What would the Ag on a plated spring weigh? Extra layers of Sterling plating would be needed for the host, but Stainless Steel and Ti have no oligodynamic properties to speak of, and Al is inferior to pure Ag or Sterling in that regard.
 

onetrickpony

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Also, if you recharge regularly at moderate discharge levels to improve battery life, then the absolute max capacity of the battery may be of less importance because you aren't using the full capacity anyway.
I don't try to run batteries down till they shut off from the protection circuit.

With IMR, it may be helpful to have a light that does shut down at 3v or something like that, so that you be relatively sure that you won't over-deplete your unprotected battery.
Lights such as the Oveready Triple have such protection, and they are basically made to use IMR cells for the most part.

There are unprotected versions of all lithium rechargeable battery types. A low voltage cutoff is advisable regardless.

Unfortunately, most pcb circuits installed on protected batteries will cut off at high amperage as well, which is why not having one on the cell is a must for high current drawing lights including many direct drive setups designed for maximum brightness.
 

BeastFlashlight

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So IMRs are dangerous to run flashlight down to battery failure? I had a question of why the hell can't IMRs be protected also buy you read my mind on that one...

Unfortunately, most pcb circuits installed on protected batteries will cut off at high amperage as well, which is why not having one on the cell is a must for high current drawing lights including many direct drive setups designed for maximum brightness.

I have Vinh modded lights that i'm using the IMRs for so kiss goodbye any low volt cut off circuits...so ok I got it I must be in the habbit of only moderately using the battery charge before recharging!!
 

onetrickpony

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Even a very basic multimeter helps a lot, but for the most part you'll be able to tell by the light dimming. Just so you're aware, most battery failures occur when trying to CHARGE a battery that has been OVER discharged. I personally dispose of any battery that gets below 2.8 volts.

Not that I condone or suggest it, but it is unlikely that a single cell light will have any problems even if you ran the battery stone dead. Just don't try to charge that battery before you check the voltage!

You could even get by with something like this Edit: I'll try to pm you a link because it may violate the forum rules :)

Another thing to consider is the lifespan of your batteries. If you consistently run them down very low they will not last as long and will lose capacity over time. It's also not recommended to store them at full charge for long periods of time, although I admit that I'm guilty of the latter.
 
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