An Idiot's Guide to 18650's - Under Construction

As a newcomer to flashlights, I found it an extremely steep learning curve to get all the information I needed. I was frequently directed to hard-to-follow info pages on all kinds of stuff; some of it was worth reading, some of it was a complete waste of time (for me).

This guide will give you the basics. The stuff in bold is stuff you NEED TO KNOW to operate an 18650 flashlight safely. Other information will be provided to help explain the stuff in bold in case you have any questions. Links will be provided at the bottom for those who wish to do some more research.

WHAT YOU RISK is literally life, limb, and home, if you choose to ignore these guidelines.

Preamble (skip if you like, but it may come in handy when reading):
What are these suckers, anyway? What’s the big problem; why can’t I just pick up some cells and start using my flashlight? Good questions! It’s probably easiest to understand if we consider what they’re NOT. What they’re not, is is a cell made for your average consumer. These cells have higher energy density, which is both their attraction and the cause of safety concerns. While the technology has come a long way in terms of safety, and a huge number of flashoholics use these cells safely, there’s enough of a safety concern that companies like Panasonic and Sanyo, who are the ACTUAL manufacturers of these cells, refuse to market them directly to the public. The manufacturers only sell these cells to other manufacturers, who must meet the primary manufacturer’s safety guidelines for their use.

So with that in mind, how do we end up with nice little cells for use in our flashlights? Another good question. The answer appears to be that other companies acquire them somehow, and repackage them as individual cells for use in things like flashlights. Of course, there are many ways a company might acquire cells. These cells are often used in things like laptop batteries. One way to acquire cells is to buy refurbished laptop batteries at huge discounts, rip them open, and salvage the cells that aren’t dead yet.

The problems with buying such cells are the similar to the problems one faces when buying a second-hand car. We don’t know how the cells have been used in the past, how much life is left in them, or if the darn things have some sort of internal problems that make them ticking time bombs. Obviously, these are not the sort of cells we’d prefer to buy, since we have no idea what we’re getting.

The reason we can’t (or shouldn’t) just blindly buy and start using without doing research, is that, under certain circumstances,
18650’s can do the following:

# Explode, turning your flashlight into a pipe bomb
# Vent toxic gas
# Start a fire that is extremely difficult to extinguish.

These are worst-case scenarios, and highly unlikely. Highly unlikely, that is, if one follows the guidelines in this guide to the best of one’s ability.
edit: as a result of improvements in safety, these primary cells are starting to make an appearance in more mainstream consumer outlets. There is, however, in the opinion of some (many?), including myself, still a place for a guide such as this.

ALWAYS EXERCISE COMMON SENSE when handling these cells; i.e., don’t try to damage them, burn them, short them, etc… If something unusual has happened to the cell, don’t use it in any way without first asking someone in the know.

A digital multimeter, or some other means of accurately taking voltage measurements, is a MUST-HAVE when using these cells. Knowing the voltage of a cell will tell you when it needs to be charged, when it’s no longer useable, when your charger is misbehaving, help diagnose problems with your flashlight, help determine when cells have become unsafe to use, and allow you to use multi-cell flashlights safely.

Before connecting your cell to anything, you should always inspect it physically for signs of damage. This includes:
1. Discoloration (signs of overheating)
2. Tears in the wrapper
3. Signs of deformation (not perfectly cylindrical anymore)

The rule, “If in doubt, leave it out,” should apply here. Bring it to the attention of someone with more experience if you have any concerns or doubts.

Before installing cells in a flashlight, or charger, always check the voltage.
voltage should read between 2.5-4.2V (some specific types of cells can be charged to a higher voltage)
Cells with a voltage lower than 2.5 should be discarded safely, according to the regulations for waste disposal in your country.
Under no circumstances should you try to charge these cells or use them in your flashlight.

[It’s been months of lurking, and I now feel reasonably comfortable having a conversation about the technology, although I still have tons to learn. But now my friend, having been impressed by my flashlights on our camping trips, is interested in picking up lights and cells. I know he has no idea what he’s getting himself into, and I always find myself tied in knots trying to explain things to him.

I was thinking this forum could benefit from an idiot’s guide to 18650’s. I don’t think I’m qualified to write it… at least not without some serious help from the forum. On the other hand, I have the time, interest, and an idea of what sort of info I’d like to include, and how to organize it.

My question is, do you guys think it’d be worth doing? Is there anyone who wants to take up the project? Or could I start an open-source kind of thread, where I post something and people can post replies when I get it wrong. Then, when it’s more-or-less finalized, have it as a sticky.

Whaddaya think?]

I think we already have it: (Linked to on the BLF homepage)

Although I would argue these are not for idiots. Batteries and electronics in general are complicated subjects. The more you learn about battery chemistry, the more you realize that idiots should not be using the ones most of us use. Not everything can be dumbed down for the masses. That's why there are alkaleaks.

I don't think having a quick guide to Li-Ion batteries is doing an end user any favors. People need to understand what can go wrong if they are not treated with respect. I have read the equivalent of a Tolstoy novel on the subject and I still consider myself a noobie compared to some of the braniacs here and on CPF. I know enough to discourage some people from using Li-Ion, because I don't believe they have the patience and attention to detail required to use them safely. I love my son to death, but I only recommend AA lights to him. Maybe when he hits his 30's....

Not that i disagree, but for those who want to learn what they need to know, we all have to start somewhere, and having a resource for those who are ready would save a lot of searching and piecing things together.
Those resources you name are not complete, they are a beginning

I mean, if we just put a sticky at the top of every section saying stuff like,

buy only good cells like” himax/tenergy/aw/kallies”,
“don’t overcharge”,
get a “multimeter(especially if using in multiple cell lights)”.
“make sure to put the cells in the right direction(usually positive towards the head)”.
“Don’t buy trustfire/ultrafire/fire cells”

In my opinion, if we basically just say that, everyone should be fine. And by the time they are buying more complicated lights, they should have read enough threads about batteries just by browsing the forums to give them a pretty good idea about lithium batteries.

Bort, you are correct. Those resources are not complete, but they are a good start and should be required reading. The flashlight wiki is maintained by BLF member brted. He is open to suggestions and you can actually mod the wiki by becoming a member and setting up an account:

I think brted would be open to adding a 'Getting Started' under the batteries section. The challenge with any wiki is getting agreement on what should be in a specific topic. Although sintro started a pretty good list there. Smile

  • Rule #1: Stay away from Ultrafire cells in all their forms, no matter how tempting the price. :slight_smile:
  • Rule #2: See Rule #1
  • Obtaining a DMM (Digital MultiMeter) and learning its applicable functions should be de rigueur for Lithium-Ion cell usage, IMO.
  • One should check voltages EVERY TIME before inserting cells into a multi-cell torch, as this is the most common setup for the dreaded VWF event - Venting With Flame. While these events are not common, it only takes one to ruin your day, blow off a finger, or burn down your house.

Ok, I think this is convincing me to do it up. I really have some strong ideas how how I wanna lay it out, and for content, but I’ll take advice every step of the way. Plus I get to have all the forum members point out all the stuff I think I know but really don’t :smiley:

100% with you on this.
If batteries look too cheap to be true- avoid them. Never mind what capacity it says on the label, with Ultrafire or GTL, you’ll be lucky to get 1000mAh, and they will probably be re-cycled laptop cells.

There’s no need for the ignorant CPF li-on paranoia to infect this forum.

Thousands of “idiots” use large unprotected 18650’s with only a handful of known incidents. Looks like empirical evidence shows that it’s not so dangerous after all.

Just don’t buy from completely disreputable sources which sometimes repackaged used battery in multiple cell light. Otherwise at worse you’re just getting ripped off.

Yeah, it's important not to scare beginners away from LiIon based cells, but to scare them enough that they look deeper into the matter of safe handling those cells. ;-) High quality protected cells and a well tested charger and a cheaper dmm are a good start.

agenthex - feel free to buy whatever you want and handle as you see fit, but I’m sticking to my recs.

Nobody said the failures were common, but they do happen with enough frequency to warrant care.

Getting “ripped off” is FAR from the worst thing that could happen…

How is a few threads of obviously dangerous handling (multiple different cell, incompetently designed custom light, etc) related to “enough frequency”?

Ignorance is bliss.

Carry on.

I do agree it’s quite ignorant to believe in mythical dangers whose most useful role seemed to be selling expensive batteries. That role seems to have disappeared, yet the myth remains.

Well, having seen a cell vent as a first hand experience, I must be one of the few mythical figures in flashlight land. The reason was a defective/damaged shrink wrap that caused a short circuit on the cell. We believe that some non-deburred aluminum surface in a cheap Ultrafire flashlight led to the damaging of the shrink wrap. Granted it was more the fault of the flashlight than the cell, but since the flashlight was getting to hot too touch without actually being turned on has been a scary experience. Luckily nobody got hurt or injured. I can wholeheartedly say... LiIon are a potentially dangerous chemistry regardless of the probability something bad can happen... but that doesn't keep me from using them.

Do I have to watch out for seagulls in the desert from now on?

If this doesn’t degenerate too badly, this is exactly the kind of debate I was hoping to see that might lead to some clarification, and possibly some guidance for n00bs that everyone can endorse :slight_smile:

My first batch of 18650’s was a bunch of blue wrapper ultrafire “3800” mah cells that were the absolute cheapest cells I could find anywhere. I think I bought 10 of them, along with 3 of the cheapest 2-cell chargers I could find.

Shortly afterwards, I started learning some stuff on the net that made me very nervous about using them. Turns out, a couple were duds after a use or two. I can still charge some of em, and I use em in cheap single-cell lights only in a pinch.

The chargers are cc/cv, and seem to get the job done. I always inspect cells for damage and test em with the dmm prior to charging. I never leave them unattended, and periodically check the heat levels while they’re charging.

I always check the voltage of the cells after charging and find that they usually to 4.2something volts. Anyone think this is cause for concern? Or just acceptable margin of error?

That depends on you DMM, assuming it is accurate I would not like a battery above 4.25 volt.

Generally a higher voltage will give more capacity and shorter lifetime on the battery. If the charger forces old batteries above 4.2 volt, it is very bad for their lifetime and will also increase the risk of "kaboom", but that is a very low risk.

When using CC/CV chargers the battery is never forced to a high voltage, the charger will stop charging at a specified current and the battery will drop a bit in voltage, how much the battery drops depends on chemistry and age of battery (Some examples for fresh batteries can be seen in all my battery tests).

Have a look at what happens when cheap Ultrafire 3000mAh vents:

If we did a lot of upgrading to this article, it should serve the purpose Gimpy is going for