1x and multiple 18650 lights - The real deal on safety?

[RCLumens]

Greetings - I read a post here not too long ago about another explosion... I believe it was a 2x CR123 mishap from the preshrink-wrapped types that are in series, so the user couldn't test voltage individually... This got me thinking as I have a Zebralight SC600, and Sunwayman T20CS, and an RRT 3X XML - Running 1x 18650's on the smaller lights and obviously 3x 18650's on the RRT3. I feel a bit better about the two smaller lights as they're running single 18650's, so no worries on any unbalancing there, but the RRT is running 3 of them. I check voltages regularly with my multimeter to make sure all batteries in the RRT 3 are balanced. There's one Batt that reads .1 or .2 different than the other two. (ie - 4.14, 4.14, 4.12) Is this a concern?

Also, if all batteries are reading balanced, or very close to it - is it common that they become unbalanced during usage? Is there a way to test?

I may be looking to buy a TK41 for my larger light, or even a TK70 to possibly replace my RRT3 - but am I becoming paranoid?? Many thanks to the experts on this awesome forum! and to all for your input. Cheers - RC

 

[GunnarGG]

There was a recent post about a Fenix PD30 with RCR123 that burned, i think it was the batteries that caused the fire.

The difference in voltage you describe isn't actually 0.1 but 0.01 between the cells.
I don't think that is a problem.
What you can do to check how balanced the cells are is to measure them after use before charge.
If two cells are, let's say, 3.9V and one cell is 3.7 or 3.8 then you have unbalanced cells.
So you shouldn't run the light further than that before charge, then you might overdischarge the lower cell.
The best is to replace the low cell, you can use it in your single cell lights.

Maybe you are becoming paranoid - so am I!
This is the reason I haven't got a multi Li-ion light.
If I had use for one and used it frequently and monitored the cells I wouldn't worry.
But in my case the light would probably be used only occasionally and I would never know what status the cells had unless checking voltage everytime I used it.

Edit: I'm not one of the experts on this forum but this is the way I think about Li-ion.

 

[LEDAdd1ct]

Had some multiple 18650/RCR123A lights and sold them off. I use my lights, and charge the batteries, and don't check voltages as often as I should. Therefore, I don't feel I have any business running 18650s in series in high power configurations.

Now, I do have a C3 with extender which I will use with a pair of protected 18650 cells and a P90 lamp in the future.

But, that will be with quality protected cells, and we are not talking insane amounts of current.

There is a level of mindfulness somewhere between paranoia and carelessness; I try and shoot for that sweet spot.

 

[DrewDT]

Interesting thought, I just bought the Sunwayman V60C with it's optional charger so I can charge the batteries without ever taking them out. They are 3 18650 protected cells. I suppose I should be checking their voltages regularly?

 

[moldyoldy]

Interesting thought, I just bought the Sunwayman V60C with it's optional charger so I can charge the batteries without ever taking them out. They are 3 18650 protected cells. I suppose I should be checking their voltages regularly?

Regularly? yes, depending on how often you use the V60.

fyi: there is a long thread on the V60 and matching charger base. The thread is currently listed near the top of page four in the Flashlight Reviews forum. Alternatively do a search on Sunwayman V60.

 

[CamoNinja]

With my V60r I charge the cells separate and check them regularly with a DMM

 

[snakyjake]

Running multiple lithium cells is the highest risk, because of the current draw that can happen from unbalanced cells. I assume this can happen with protected cells since there's nothing preventing a maximum current draw, nor is there a temperature circuit breaker.

The next risk is the over dis/charging.

I deplete my batteries down to nothing because of the environment I use them in (working, caving, hiking). I won't be checking voltages. I'm going to use LiFePO for my current lithium lights, and wanting to switch to NiMH.

 

[45/70]

Whenever you run multiple 18650 cells, or any Li-Ion cell, in series in a light, there is some amount of risk involved. The use of 18650 cells in flashlights/torches was invented/pioneered here on CPF by the custom light makers, who pulled cells from laptop battery packs and built lights around them, not the light manufacturers. This was back around the turn of the century, when the Forums were called Candle Power Forums, before it became Chinese Phlashlight Forums.

Since no lights that I am aware of, or the battery packs used in them, include protection circuitry that monitors each individual cell in the battery "pack", there is always going to be a certain amount of risk involved when using Li-Ion cells in series. The only way to play it as safe as is possible, is to use only protected cells when using Li-Ion cells in series. Even in this case, you are hoping that the protection circuit that has been added to each individual cell by a third party (Li-Ion cell manufacturers do not produce Li-Ion cells with added protection circuits, the liability factor is too great), actually works.

While we're on the subject of protection circuits that have been added to manufacturer's cells, that too was actually invented by a CPF member. I don't know the whole story, but I do know after the member went to a lot of trouble and expense to come up with the "protected Li-Ion cell", the idea was basically stolen from him after a considerable amount of time and investment. He ended up loosing his a$$. Anyway, that's where individual protected Li-Ion cells originated.

One should always be vigilant when using Li-Ion cells in series. Keep track of the cells to be sure they are well matched by monitoring each cell's voltage, throughout discharge initially, and then every once in a while whenever using a light with Li-Ion cells in series. This includes when using protected cells. You can't be 100% reliant (or shouldn't be, anyway) on the protection circuits that have been added to cells.

Our use (regardless of what the light manufacturers would like you to think) is a "custom use" of Li-Ion cells. They were never intended to be used in flashlights/torches. As I said, be vigilant, and all should go well, without any problems.

Dave

 

[GunnarGG]

It would actually be nice if each cell was monitored in multi cell lights.
One thought I just had was a triple LED light with 3x18650 that was wired so it was working like 3 single LED, single 18650 lights packed in one house.

 

[RCLumens]

Thank you for these awesome answers!

 

[Onthelightside]

I have a 2x CR123 light which I replaced with a single 17670 li-ion to make it a single celled light and I think safer

 

[tzt]

The risk is greatly exaggerated on this forum. The vaulted Surefires used 2x lithiums with fairly rare instances of catastrophic failure. Of course Surefire is magic and physics need not apply. :laughing:

 

[Shadowww]

The risk is greatly exaggerated on this forum. The vaulted Surefires used 2x lithiums with fairly rare instances of catastrophic failure. Of course Surefire is magic and physics need not apply. :laughing:

Well, SureFire's 123's are USA-made, while most of catastrophic failures seem to happen with Chinese-made CR123's (Golston, Titanium Innovations, 4Sevens)

 

[tzt]

Well, SureFire's 123's are USA-made, while most of catastrophic failures seem to happen with Chinese-made CR123's (Golston, Titanium Innovations, 4Sevens)

There's no magic from manufacturing things in the US either. Most batteries (like most things) are made in china, thus a likely statistical bias.

 

[yellow]

this can happen with protected cells since there's nothing preventing a maximum current draw, nor is there a temperature circuit breaker.

all my protected cells feature:
* overvoltage protection (while being charged)
* undervoltage protection (when in use) and also
* overcurrent protection

Thats the reason to use protected cells: not to have to care anymore for anything

 

[snakyjake]

Thanks "yellow"....though my quote should have included "assume".

 

[Shadowww]

all my protected cells feature:
* overvoltage protection (while being charged)
* undervoltage protection (when in use) and also
* overcurrent protection

Thats the reason to use protected cells: not to have to care anymore for anything

The problem is that usually overcurrent protections are set too high on protected batteries (for example - RediLast 3100mAh trips at 12 amps, while max. recommended current for that cell is 6 amps). So it's not "overcurrent protection" but more like short-circuit protection.

 

[yellow]

hmm,
:thinking:
those values - both - seem much too high, but I do not remember having ever read any data/mesurements

Imho thats current where normal protection already should have kicked in, thats IMR cells high discharge power territory.

 

[Shadowww]

hmm,
:thinking:
those values - both - seem much too high, but I do not remember having ever read any data/mesurements

Imho thats current where normal protection already should have kicked in, thats IMR cells high discharge power territory.

6A for 3100mAh cell is not too high, it's under 2C (which would be 6.2A).
And 12A is indeed too high, but RediLast's protection circuit doesn't minds cell being discharged at current that high, apparently.