Most likely situations where 2 or more cells in series were used. One cell depleted and the others reverse charged it.
The Panasonic 3400mah can be drained to 2.5v safely. I don’t use a fire proof bag or anything while charging. But I do have them very close to me while charging and never leave them unattended just incase. I have seen ads that say the S5 has a low voltage warning, I don’t know if this is the case with yours. If it does you should be fine using it to tell when the battery is running low given the Panasonics can be discharged down to 2.5v, even though most times you will have already charged it before it even happens.
If its piece of mind you want remove the spring on the driver and solder a small blob on there and see if a protected cell will fit. Maybe something shorter might help too. You can look at HKJ site and find out all the different lengths for several quality batteries with pcb’s. Battery test-review 18650 summary
Maybe some Sanyo 2600mah will fit.
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If it has 3-amc7135’s then it should be a 1000ma version which would give you a run time of a little over 3hrs with the 3400mah. The 2600mah should run a little over 2.5hrs.
Better so start out extra cautious.
More people should be as cautious as Chloe. Seriously, you talk to some people using li-ions and its just clear they shouldn’t be anywhere near one. It a risk not only to themselves but anyone they live with. Need to have at least a little respect for the energy they pack into that little metal shell.
What do a couple precautions actually cost?
One of the random venting cells was a Panasonic CGR18650CH. Bad timing that this thread started just when I had ordered some cells:
http://www.fasttech.com/forums/1141101/t/1029637/be-careful-exploded-while-not-even-in-use
I can’t remember the other (it was on the other forum) but I know it involved hydrofluoric acid, really awful.
But there are many other unknown factors.
Better to be safe than sorry. :_(
Sometimes its not the battery that causes the fire with flames either, charges have been known to go poof too.
Never charge li-ions unattended, you could seriously burn down your house.
Yes, you’re right. I was thinking even though the ML-102 can be powered from a netbook I would rather use my 1A USB power supply as I’ve read even spikes etc. may cause problems charging.
It’s a little less convenient but even observing my phone charging with a charger doctor makes me think there might be something to it.
Sounds like you would be safer with Li-Co cells then 90% of the people using them. 
I mean there are lots of e-cig users are out there now & many stores sell li-ions without informing them of any precautions.
Do you put your cell phone in a lipo charging bag? Or you laptop in a lipo charging bag, that uses uses several cells?
Would you fear driving a Tesla Models S, using around 7000 NCR18650 batteries? (Even in crash tests its doing great in terms of battery safety and everything)
Im all for safety, but after reading on BLF on li-ion safety you can easily end up getting a bit paranoid about the safety of li-ion cells in general.
How many thousands of 18650 cells do you think get produced on a daily basis? The very few cases I have heard of causing any damage have used crappy (Ultra)Fire cells, in crappy chargers, and combined with lights using a series-setup and no checking on the batteries.
There have been reports of cell-phones blowing up and such too. Li-ions are not 100% safe. Living, walking out of the house and such are not 100% safe either. Considering the amount of li-ion cells that is around, there is really no need to worry as long as you get some good cells and don't abuse them in any way.
When that is said, I prefer protected cells, because I have managed to run into the protection on some cells a few times (either due to extreme drain, not something you should worry about unless you are doing some extreme current modifications to some lights. Or due to badly designed light,possibility of tail/driver spring and retaining ring connecting to the battery at the same time. Or due to user error when trying something..
3x350mA regulators gives you 1050mA. 1 amp aint much. 18650 cells can do 1amp all day long, at least until they are empty.
Im not sure which cell to recommend you if you are going the unprotected route though. So this reply may not be that helpful, but using a single cell in a flashlight is not much to worry about in general. On top of that the nanjg 105C also have built in low voltage warning, so when using the light there is nothing to worry about, because you will be warned with blinking/dimming. You could end up draining a battery if the light gets accidentally tuned on, but if you have the light in a bag, purse or something. Just unscrew the tailcap or body a little. On most lights that cuts the connection and renders the tailcap useless for accidental activation.
I either stick to protected batteries, or high drain batteries without protection. If I use high drain, I often combine with a Qlite driver or something. That driver cuts off the light when cell voltage gets very low, but first it warns you. :) Its basically idiot proof.
I particular don’t like to carry a light in my pocket that doesn’t not have a protection circuit.
I have had a twisty light come on before in my pocket and didn’t even know it, until I felt something getting warm down there. It didn’t catch fire or anything it was just on heating up my leg.
Without a pcb and the drive current being less it could have drained the battery to the place of no return without me even knowing it. I will not EDC a light without a protected battery for that reason.
Thanks you all! I feel a bit better now.
I got the Li-Po bag and thermometer and will make some leads with magnets for charging. Unfortunately I don’t think protected cells fit into the Convoy S5 diameter-wise even if I trimmed the springs they won’t fit.
Oh, the Convoy S5 has a firm clicky so I am confident it will not accidentally turn on when it’s in my coat or handbag.
Aww, thanks anyway! There is still time to cancel that item as one of the things in my order won’t be in stock for a few days yet.
I’d like to re-recommend the AW IMR 2000mAh 18650. It fits easily and is a much safer chemistry. 
Where can I get the AW? I think I would prefer that.
Nevermind, found them* for sale on the other forum.
Honestly any quality 18650 will be fine. You will notice the massive drop in output before you over discharge the li ion. Anybody who runs their protected cells to cut off is already doing it wrong. With an in protected once high stops being much brighter than medium, time to charge.
Protection is only a back up. It isn’t a magical fix to make the battery never explode. All it does is protect the battery from chargers that over charge, users who never re charge their batteries, and shorts. I prefer unprotected because the protection circuit hurts battery performance.
+1
+2
Thanks, bdiddle! It’s my first Li-ion light and that really helps to know. I always notice any output loss with my other lights.
AMEN, Brother!
But let’s all agree to not quit something, throw away something useful, just because one has to think about what they’re doing when using it, please?
Gasoline can turn a Buddhist Monk into a raging political firestorm, but it can also take him to a Baskin Robbins for the treat of his life!
Wait until you see what high-purity Hydrogen Peroxide can do (especially with a taste of one of the “anes” like Butane mixed in) in the drive chamber of an electric turbine… IFF we can just get people to quit believing they’re afraid of H2O2… (and to pay attention while using it)
In MY dreams, yeahbuddy!
Dim
Chloe, ive observed in the little time ive been here, that you are more than qualified to handle 18650 cells, you will be fine
A little caution goes a long way when charging any battery, but consider the average household that leave batteries in chargers for days unattended?
Camera batteries, mostly Li-Ion
Power tool batteries, NI-Cd, NiMh , Li-Ion
Cell phones, Li-Ion
Tablets,Li-Ion
Laptops, Li-Ion- people charge the hell out of these things especially when the battery is long gone, the dinky protection inside must kick in continuously.
AA Nimh cells left in dumb chargers for days (friends of mine do this)
Ok most Li-Ion are under the battery pack protection , but nothing will help you if the unlikely event occurs of a venting or thermal runaway, I’ve been charging batteries since 1975 in the old days of Ni-Cd without problems in home made chargers.
In fact Ni-Cd are known for thermal runaways, and are installed in budget power tools with no protection whatsoever (I have one and have opened it to see if I can mod to Li-Ion)
I recently modded / repaired a Li-Ion power tool pack, only one thermal sensor inside under a single cell out of 5 (18V pack), and 2 cells were at 0V, the others all at 4V when I tested them, and this power pack was sitting in a charger for days.
I have dozens of unprotected Li-Ion harvested from laptops, all tested and the duds recycled away, I use the good ones for all my single 18650 lights.
I don’t however charge unattended any battery whether its an eneloop or Li-Ion, lead acid , any decent charger can fail.