Dive light from E-Bay -- Great buy!!!

[spoolin01]

dberry, what batteries are you using? I'm using the Efest IMR 26650 batteries, 3500mAh 64A 3.7v. After about 30 minutes or so I've probably lost more than 75% of the light output. At that point my 450 lumen big blue light is brighter that this one.

And yes, I'm using the same light from the original ebay link that ships out of Hacienda Heights, CA.

I'm still learning about this stuff, but I gather that IMR batteries are slightly lower capacity than the more common ICR chemistry - what most are probably using. They are specifically high drain rate capable, but from what little I've read and seen from testing so far, these lights are kind of on the border of the current draw rate where the switch from ICR (protected batteries are generally ICR from what I've read) to IMR is recommended.

However, the specs you see for IMR vs ICR wouldn't explain much difference in run time due to capacity alone, unless there's something about the high drain batteries that allows them to feed the light more current than the ICR or lower-drain rated type, so that they run down faster. That's purely a guess, and my protected (probably ICR) cheapo Ultrafire batteries run down about the same time that yours do.

I'm using a good charger, and also have checked voltage of the charged batteries many times, so I know I'm getting a full charge (4.2V termination). On my charger/analyzer, my batteries tested around 2900mAh at 750mA drain rate from full charge. That seems consistent with typical capacity specs for 'reputable' batteries, despite the absurd 6000mAh claim that UltraFire makes.

It's also possible that there are differences in the various lights themselves that folks here have gotten. Since the one I own, and apparently at least a couple of the others, are not current-regulated, it's possible that whatever minimal regulating circuitry is being used - if any is there - is not the same in all the units. Also, different individual LEDs have different Vf parameters, which is a measure of how much voltage is required by the LED (I don't yet understand exactly what this represents, but it's some kind of non-absolute limit, below which brightness drops off). Vf is usually just above 3V from what I've read, so in a single LiIon battery flashlight, the battery is barely providing enough voltage, and an LED with a slightly lower Vf requirement should result in a light which stays brighter longer. Again, it seems unlikely this could be the major factor explaining the reported 2x-3x different run times here - I don't think Vf individuality is that great.

It would help to have better data. In particular, those reporting long run times who have more than one light and battery could do a simple experiment: after dark one evening, take two lights with fully charged matched batteries, and turn one of for 45 minutes or an hour. Then compare the light output to the second flashlight, and see if there's a difference, and how much. It would also be helpful to take a voltage measurement of the battery, after letting it rest a half hour or so. If that voltage is below 3.0V, the battery is being run too low. From what I recall reading, recharging after over-discharge is the real danger with Li-Ion batteries, especially ICR chemistry.

An important note to the above experiment: if you can do that 'on land' for anywhere near 45 minutes without the light becoming too hot to touch (and probably compromising the LEDs), then we don't have the same lights. I can run most of my other, current-regulated, underwater lights for long periods on land, without them even becoming very warm, if at all. It would be best to do the long drain test in a good sized tub of water.

 

[oldschoolto]

I don't understand the drawdown of the battery ? How am I to know what voltage is when using it ? The light was still bright after the 30+ minutes of shooting video. Got home next morning and but them in the charger.

Are you saying you can't let the light go dead from being on without ruining the battery's?

Jim...

 

[spoolin01]

The best way to monitor voltage is with a digital voltmeter - a pretty handy tool for lots of things including rechargeable battery usage. The charger/analyzers like Nitecore, Opus, and a couple of others, and the hobby chargers (from the RC world), will show voltage but I don't know that you can have confidence that they are displaying simple starting voltage for the inserted cell - at least for very long - and not some value during the charge or discharge process.

From what I've been reading about Li-Ion batteries, it seems that they can be damaged when voltage drops too low. Exactly what the parameters of that risk are is tough to nail down - I've seen 'threshholds' cited anywhere from 2.0V to just above 3V, and it probably has a strong duration component - but it becomes more murky when you consider that there can be an enormous difference between the instantaneous voltage under load and resting voltage after rebound, as much as a volt or more if the drain current is high.

Most of the charger/analyzers seem to use a terminal discharge voltage of 2.7V - that's instantaneous voltage. Many users recommend higher working minimums for prolonged battery life. If you look at the many tests of Li-Ion batteries online, you see that most of the capacity is gone once voltage drops below 3.5V

I've read that there are chemical changes to the battery while at low voltage, involving copper formation or migration, that are permament and damaging. The damage can apparently lead to increased internal short circuit risk - which can lead to fire and even explosion under some conditions (such as containment in a pressure vessel like a dive light). The regular advice seems to be NOT to attempt to recharge a battery that has gone to low voltage for any period of time.

Here's a quote from candlepowerforums from 2012. Loose Li-Ion batteries have only become commonly available in the last 8 years or so apparently, and the battery technology usage overall is also fairly recent, so understanding of the technology in the consumer population is fairly recent in development. Much of what you read on some sites relates to battery packs - e.g. laptop batteries - which add another layer of management risk over single cells. So determining what's authoritative about use in this situation is not easy. I have noticed that the warning against not recharging over-discharged batteries enjoys a high level of consensus.

"When a lithium-ion cell is overdischarged, the copper current collector on the negative electrode begins to dissolve. The copper ions diffuse away from the current collector, through the electrode and the separator. When you attempt to charge the cell, the copper replates as metallic copper, which can bridge the separator and cause internal short circuits. Normally, a cell with substantial copper short circuits is no danger because you can never charge it up...it is essentially a resister. However, occasionally these internal short circuits don't activate until the cell reaches full state of charge, and this can result in a very energetic (i.e. explosive) reaction. Very dangerous. The exact voltage where this occurs depends upon the cell design, but a good rule of thumb is to never let the open circuit voltage get below 2.5 V.

In addition to the safety issues, an overdischarged lithium-ion cell will likely have permanent capacity loss and increased internal resistance, even if no copper has dissolved.

For these reasons, recharging a cell that has an open circuit voltage of less then 2.5 V is generally not recommended."

You can read the whole thread here, including qualifying comments. I only located that thread just now, but it summarizes what can be found elsewhere in the Li-Ion discussions.

There seem to be three large hobby communities that use lithium-based batteries widely - radio controlled vehicles, flashlights, and of late, vaping devices. The RC crowd doesn't seem to use Li-Ion much so what you read on their sites relates mostly to LiPo and isn't so applicable here. There is an enormous amount of safety- and use-related Li-Ion battery stuff on candlepowerforums, including participation by apparent manufacturers. Sifting through it all can be tedious.

 

[oldschoolto]

The best way to monitor voltage is with a digital voltmeter - a pretty handy tool for lots of things including rechargeable battery usage. The charger/analyzers like Nitecore, Opus, and a couple of others, and the hobby chargers (from the RC world), will show voltage but I don't know that you can have confidence that they are displaying simple starting voltage for the inserted cell - at least for very long - and not some value during the charge or discharge process.

From what I've been reading about Li-Ion batteries, it seems that they can be damaged when voltage drops too low. Exactly what the parameters of that risk are is tough to nail down - I've seen 'threshholds' cited anywhere from 2.0V to just above 3V, and it probably has a strong duration component - but it becomes more murky when you consider that there can be an enormous difference between the instantaneous voltage under load and resting voltage after rebound, as much as a volt or more if the drain current is high.

Most of the charger/analyzers seem to use a terminal discharge voltage of 2.7V - that's instantaneous voltage. Many users recommend higher working minimums for prolonged battery life. If you look at the many tests of Li-Ion batteries online, you see that most of the capacity is gone once voltage drops below 3.5V

I've read that there are chemical changes to the battery while at low voltage, involving copper formation or migration, that are permament and damaging. The damage can apparently lead to increased internal short circuit risk - which can lead to fire and even explosion under some conditions (such as containment in a pressure vessel like a dive light). The regular advice seems to be NOT to attempt to recharge a battery that has gone to low voltage for any period of time.

Here's a quote from candlepowerforums from 2012. Loose Li-Ion batteries have only become commonly available in the last 8 years or so apparently, and the battery technology usage overall is also fairly recent, so understanding of the technology in the consumer population is fairly recent in development. Much of what you read on some sites relates to battery packs - e.g. laptop batteries - which add another layer of management risk over single cells. So determining what's authoritative about use in this situation is not easy. I have noticed that the warning against not recharging over-discharged batteries enjoys a high level of consensus.

"When a lithium-ion cell is overdischarged, the copper current collector on the negative electrode begins to dissolve. The copper ions diffuse away from the current collector, through the electrode and the separator. When you attempt to charge the cell, the copper replates as metallic copper, which can bridge the separator and cause internal short circuits. Normally, a cell with substantial copper short circuits is no danger because you can never charge it up...it is essentially a resister. However, occasionally these internal short circuits don't activate until the cell reaches full state of charge, and this can result in a very energetic (i.e. explosive) reaction. Very dangerous. The exact voltage where this occurs depends upon the cell design, but a good rule of thumb is to never let the open circuit voltage get below 2.5 V.

In addition to the safety issues, an overdischarged lithium-ion cell will likely have permanent capacity loss and increased internal resistance, even if no copper has dissolved.

For these reasons, recharging a cell that has an open circuit voltage of less then 2.5 V is generally not recommended."

You can read the whole thread here, including qualifying comments. I only located that thread just now, but it summarizes what can be found elsewhere in the Li-Ion discussions.

There seem to be three large hobby communities that use lithium-based batteries widely - radio controlled vehicles, flashlights, and of late, vaping devices. The RC crowd doesn't seem to use Li-Ion much so what you read on their sites relates mostly to LiPo and isn't so applicable here. There is an enormous amount of safety- and use-related Li-Ion battery stuff on candlepowerforums, including participation by apparent manufacturers. Sifting through it all can be tedious.

But it still somehow doesn't make sense to use a Li-lon battery in a flash light if running the battery down that low is a big problem... Same goes for battery power tools that are always used till they don't Work and then you swap the battery's for one in the charger and get back to work... They don't have a warning light that tells you to stop using it and recharge... Everyone I know runs them dead and s charges without problems...

Jim..

 

[spoolin01]

Li-Ion battery packs (laptops and power tools, Tesla cars) have protective circuitry to prevent over-discharge from happening. So "dead" is defined by the circuitry - it shuts down voltage availability to protect the pack - not by the lack of at least 'some' charge left in the battery. I believe I have even read that some protective circuitry in laptop batteries is designed to permanently disable the battery once it has dropped too low. This is notwithstanding that there is at the same time circuitry to prevent that from happening - but self discharge can apparently take a battery at the 'low, but permissable' voltage to a level below the design safety spec if it sits too long.

Some loose cells have simplified versions of this protective circuitry, some don't. Most often, you see the emphatic advice to use protected cells where possible, unless you know and pay attention to what you are doing. The nature of that protection in the context of loose cells is not always clear - but is often said to include over-discharge protection. Does yours?

I'm by no means personally knowledgeable about this stuff. I'm just parroting what I read elsewhere. But caveats regarding careless use of Li-Ion batteries are fairly universal where discussions of use take place, and the anecdotes of what can go wrong demand respect for their severity. Many people have been injured and had even severe property damage, from using Li-Ion batteries. It is not always directly their fault - but seems often associated with choices to use unproven or budget items. Again, use of loose Li-Ion cells is a fairly recent situation, and you regularly see the admonishment that the experience gained from NiMH and NiCd batteries does not begin to match what is needed to safely use Li-Ion.

Here is my final cautionary thought about our particular application. A primary safety feature built into all Li-Ion cells from what I've read, is the ability to vent pressure should the chemistry start to run away. Typically this venting produces gas and heat and may even be somewhat violent, and in the extreme can cause fire, but is rarely truly explosive. So what do we do? - we make a pipe bomb out of it by sealing it in a dive light.

It's worth repeating - one of the most consistent bits of safety advice I've seen about using Li-Ion batteries is not to over-discharge, due to the risk of creating internal shorts in the battery that can lead to runaway thermal decomposition during later charging or use.

I think especially if you're going to use this light - which does not incorporate the regulating circuitry common to almost all other high performance lights (which provides more evident visual notice when voltage has dropped too far) - it is wise to monitor voltage drop in the batteries using a voltmeter, starting with where YOUR battery sits after just 30 minutes of runtime on high in YOUR light, letting it first rest a quarter hour or more to provide a more meaningful test of the discharge level.

 

[oldschoolto]

I guess I got some reading to do .... Thank you for the heads up....

Jim...

 

[spoolin01]

Short version:

I highly recommend that anyone considering using one of the cheapest high-current drain flashlights available, using the most thermally unstable battery chemistry available, with the largest loose Li-Ion battery made, sealed inside a pressure vessel or left charging unattended in their house, under conditions strongly suggested to risk the integrity of the battery, go over to candlepowerforums and read up about what they are doing.

/nag off

Having said that yet again - I like what the light seems to be able to do. I've recently ordered a 2x 26650 version of a 3x Cree LED dive light from eBay, to compare. I just want to bone up on what I am doing as well.

 

[dberry]

It would help to have better data. In particular, those reporting long run times who have more than one light and battery could do a simple experiment: after dark one evening, take two lights with fully charged matched batteries, and turn one of for 45 minutes or an hour. Then compare the light output to the second flashlight, and see if there's a difference, and how much. It would also be helpful to take a voltage measurement of the battery, after letting it rest a half hour or so. If that voltage is below 3.0V, the battery is being run too low. From what I recall reading, recharging after over-discharge is the real danger with Li-Ion batteries, especially ICR chemistry.

An important note to the above experiment: if you can do that 'on land' for anywhere near 45 minutes without the light becoming too hot to touch (and probably compromising the LEDs), then we don't have the same lights. I can run most of my other, current-regulated, underwater lights for long periods on land, without them even becoming very warm, if at all. It would be best to do the long drain test in a good sized tub of water.

I'm all for better data, and I have two identical lights and 2 batteries, and my charger displays battery voltage. To go one better on the experiment, I'll take some photos at T=0, 15, 30, and 45 with the control light turned off (except while taking the photos) - that'll give a fairly decent idea of the brightness relative to T=0 at the different run times.

FWIW, the light does get rather warm in air (and I have run it for an hour in a bucket of water, too.) The light beam is also intense enough to warm my hand held 6 inches in front of the lens.

I'll report back in a day or two, after I find time to give it a try.
-Don

 

[DoubleAA]

I purchased two of these and figured I would compare it with my other cheap DGX600 light.

Here is a picture of the eBay light on the left and the dgx600 on the right. 26650 on the eBay light and an 18650 on the DGX.

Sent from my iPhone using Tapatalk

 

[Narcd_dvr]

My 5000 Lumen 60m 3 CREE XM L T6 LED Diving Flashlight just arrived this afternoon and I noticed there are only 3 (On, Off, SOS) modes instead of 8 as advertised. Anyone have this problem?