Safety

[djcombes]

Can anyone comment on the safety of discharging such small unprotected Li ion cells at such high currents (3C)?

I'm sure that this must have been given some careful thought, especially since unprotected Li ion cells are sold for use with the light (from the UK). In the UK General Product Safety Regulations require that producers and distributors place on the market (or supply) only products that are safe in normal or reasonable foreseeable use.

If I were selling them, anything less than idiot proof would keep me awake at night. Any comments?

 

[Erasmus]

Well it doesn't keep me awake. I asked a lot of questions about it before I bought one, because I was concerned about this. But there are so many people who use a Wee daily without any problem, so I don't worry too much. I carried one for half a year and had no problem. After that half year my girlfriend was suddenly the owner of the light, she loves it and had no problem with it so far. Except when she was on holiday in Czech, it blew away a 4D incan of the travel leader, she almost lost the Wee because he offered quite some money for it

 

[Erasmus]

- double post deleted -

 

[djcombes]

So are unprotected Li Ions safe then? Under what circumstances are they unsafe?

It also says on the AW cell thread that the nano is unsuitable for charging the Wee cell.

There seems to be lots of conflicting advice and I'm confused.

 

[Jay R]

I use the Nano AAA charger to charge my Wee cell. Charge time is around two to three hours which makes it a safe charge rate for a Li Ion.
I'd say that AW is just covering his arse like every vendor has to these days.
Never had any worries on discharging the cells. I have, by accident, run a few Lithium Ion AAA unprotected cells to totally flat ( on high in a Fenix L0P) and the only untoward thing to come of it was that I had to throw them away after because they wouldn't hold a charge any more.
I'd worry much more if I were walking around with a box of matches in my pocket.

Every now and again there is a 'buzz' of conversation on how dangerous they may or may not be but I've heard of more protected computer batteries catching fire than unprotected cells.

 

[Kilovolt]

Being somewhat worried myself I have recently made a check with my wife's Wee.

I have fully charged the battery and then left the light on for 45 minutes (it's a 25 lumens Wee). At this point the battery's voltage was 3.1 V. I have then put the 10180 in the Nano and measured the current. The battery's nominal capacity is 90 mAh.
The initial draw was 100 mA but it lasted for a very short time, dropping soon to 80 mA and after 5 minutes to 60 mA. After 30 minutes the current was down to 30 mA where it stayed until the complete charge.

My conclusion is that this kind of charge is safe enough even if we can't expect the battery to last for too many years.

 

[djcombes]

What about a 100 lumen Wee? That would be pulling a lot of current for such a small cell wouldn't it? What happens if you inadvertently leave a torch with an unprotected cell on overnight? That's bad isn't it?

 

[Jarl]

when you wake up, you have a torch with a useless battery in it.

Simple really.

 

[zipplet]

I have performed rundown tests of various light engines (I have 25, 50 and 100) on the Wee and Raw lights. In all cases, even if I run the light until it dims very noticeably and becomes almost useless, measuring the battery voltage after a 15 minute rest gives me a safe voltage. Battery wasn't ruined.

You'd only ruin it if you continued to run it for a long time past when it dims very noticeably to feeble output.

 

[djcombes]

So are you saying that the information in this post is wrong?

http://www.candlepowerforums.com/vb/showpost.php?p=1258756&postcount=15

It states that pulling more than 2C from a Li Ion cell can result in plating of Li at the anode, which can lead to dendritic growth which can short the cell - boom.

This post directly states that the way that cells are used in Orb Raw is potentially dangerous

http://www.candlepowerforums.com/vb/showpost.php?p=1262947&postcount=29

Are these all wrong then? I thought NewBie sounded pretty plausible/knowledgeable?

 

[djcombes]

I use the Nano AAA charger to charge my Wee cell. Charge time is around two to three hours which makes it a safe charge rate for a Li Ion.
I'd say that AW is just covering his arse like every vendor has to these days.
Never had any worries on discharging the cells. I have, by accident, run a few Lithium Ion AAA unprotected cells to totally flat ( on high in a Fenix L0P) and the only untoward thing to come of it was that I had to throw them away after because they wouldn't hold a charge any more.
I'd worry much more if I were walking around with a box of matches in my pocket.

Every now and again there is a 'buzz' of conversation on how dangerous they may or may not be but I've heard of more protected computer batteries catching fire than unprotected cells.

If every vendor has to cover their arse, doesn't that apply more to Lummi than AW. He's in the UK; AW isn't. As for people finding that unprotected cells don't do anything bad when fully discharged - just because it didn't for you does not necessarily mean the risk is negligable. Hardly anyone has had a problem with using lithium primary cells in series, but several poeple have had flashlights go off like little fireworks.

It's possible to be too paranoid as a buyer, but as a vendor? From what I've read, I'd be tempted to supply the flashlights without cells and charger if I was Lummi.

 

[zipplet]

No I'm not referring to the discharge rate, rather the voltage at which the cell is once the light dims (as some people have worried that it's difficult to know when to recharge).

As for the discharge rate... well... (I don't know what to say)

Edit: Also, by "fully discharge" I mean discharge until the light dims. At this point the cell does not seem to be overdischarged *however* I'd always recharge a bit before this point to prolong cell life.

 

[djcombes]

Also here:

http://www.candlepowerforums.com/vb/showpost.php?p=1274778&postcount=45

NewBie states

"Just pushing the Li-Ion cells outside their ratings is a dangerous thing to do. The interesting thing is that once the cell is abused, the potential for a disasterous event increases. Many of the folks that are hurt by Li-Ion cells each year, were not caused by the user abusing the cells at that time. Often it comes at a later point, due to what the cell was exposed to earlier.

It is also dangerous to push a single cell outside it's specification, it is not an issue with just a multiple cell senario.

You don't have to be abusing the cell at the time, in order for the event to occur.

An example would be when a dendrite growth is created, or when Lithium is plated out of the chemistry due to the cell being pushed beyond it's rating. The Li-Ion has a maximum discharge rating (and on plenty of cells it is not 2C). Pushing it beyond this rating results in the normal Lithium Ion exchange not to occur properly, and things don't recombine as they would normally, keeping everything in the Ion transfer state. This results in a layer of raw Lithium, which is just waiting to start a chain reaction. Pushing them beyond their rating also causes dendrite growth, which can form a near short within the cell, just waiting for something to happen that closes the path for an actual short."

Reading the technical literature on the subject, it would appear that Lithium dendrite growth is a major failure mode for Li ion cells. Excessive current in discharge or charging both accelerate dendrite growth. Dendrites lead to a loss of cell capacity and can lead to shorting.

 

[orb]

I would have liked to stay out of this thread as all responses from Lummi users had hopefully reassured any safety questions.

I am not going to challenge the recommendations of Li ion cells. I can say 100% that in the 4 years + of supplying thousands of Li ion cells in my Lummi lights that I have never had one single report of any issues such as shorting or thermal run away.
Also be aware I am not the only manufacture to use RCR2's, 14250 & 10180 cells.

On a current note the Raw NS/Ti & Al with 300Ma 14250 cell Running on high will be pulling about 700Ma from a fully charged cell, this being just over 2C. Also it will only be just over 2C for a short time due to the relatively low capacity of the cells used by Lummi.

We do offer many other options & settings that provide allot of light from a small package if the brightest options are of any concern to you.
I hope that reassures & helps.

 

[djcombes]

I would have liked to stay out of this thread as all responses from Lummi users had hopefully reassured any safety questions.

I am not going to challenge the recommendations of Li ion cells. I can say 100% that in the 4 years + of supplying thousands of Li ion cells in my Lummi lights that I have never had one single report of any issues such as shorting or thermal run away.
Also be aware I am not the only manufacture to use RCR2's, 14250 & 10180 cells.

On a current note the Raw NS/Ti & Al with 300Ma 14250 cell Running on high will be pulling about 700Ma from a fully charged cell, this being just over 2C. Also it will only be just over 2C for a short time due to the relatively low capacity of the cells used by Lummi.

We do offer many other options & settings that provide allot of light from a small package if the brightest options are of any concern to you.
I hope that reassures & helps.

Thanks for the information - that does help. Like I said, I'm new to this and I was hoping for reassurance more than anything. Now I just need to save my pennies.

I think it's great what you are doing and I really admire your work. I tend to take my (small) kids on holiday to Mortehoe (camp or stay overlooking the point) which is just down the road from you. Nice part of the world.

 

[Jay R]

Hardly anyone has had a problem with using lithium primary cells in series, but several poeple have had flashlights go off like little fireworks.

Only if you little firework gets a bit warm and goes pop ( Pretty unimpresive for a firework, I'd ask for your money back.). Don't breathe any vapour though.

You are correct, several people have had problems in their lights but I believe that most of them were multicell lights with unevenly charged cells. There have been very few cases of single cells venting in lights. I've been a member here for some years and can only remember two or perhaps three cases. None of them Lummi lights. Perhaps it seems more because of the attention paid to to it in this forum on the rare occasion when it happens.

Note that there are quite a few hotwire builds and custom built lights that exceed the recommended current for their Lithuium Ion cells.