Li-ion Battery Safety and Shopping Guide

Gords pointed out this could be useful so here it is.

Proper Use of 18650s

The proper use of li-ion batteries is a quite complex issue, and one of the most important as misuse of them can lead to an explosion.

What is a Li-ion Battery?

Lithium Ion batteries are very popular in flashlights for a number of reasons. One reason is that the voltage of the battery is very close to the voltage required by most LEDs. This makes it much easier to have them run an LED. They also hold a large amount of power in a small space, they are much more energy dense than Alkaline batteries. This is because unlike alkaline batteries, lithium batteries hold almost as much power at a 3 amp draw as at a 1 amp draw. The other advantage is they are rechargeable, this means we can use our flashlights as much as we want since they simply have to be recharged.

There are 2 main types of Lithium Ion batteries, the first and most common is the LiCo cell. (Lithium Cobalt) these are the cells used in laptop batteries along with many power tool batteries. They have a nominal voltage of 3.7 volts and are 4.2 volts when fully charged. Most of them can be run down to 3 volts, before you should stop using them and recharge them. They can generally supply around 5 amps maximum.

Another type of battery that is very similar to the LiCo cell is the LiMn cell or what is know as an IMR cell. LiMn cells can supply over 20 amps so are great for high current situations. Naturally, something that can supply so much power is quite dangerous if shorted. In some cases they are safer though since they do not catch on fire or explode violently if punctured or crushed.

Both LiMn and LiCo cells have the same voltage, but the LiCo cells tend to have a higher capacity than LiMn cells. Since their voltage varies a large amount during discharge the discharge curve will look like this.

The other main type of Li-ion battery is LiFePo4. Unlike LiCo batteries they have a lower voltage. They have a nominal voltage of 3.2 volts and are 3.5 fully charged. They are considered “dead” when they reach 3 volts. It is because of this that they have a very flat discharge curve. (See Below) They are also much safer, unlike a LiCo cell it is very hard to make them explode or react violently. Because of this LiFePo4 cells are not made with protection circuits. The disadvantage to LiFePo4 batteries is twofold. First, they have a lower capacity. Second, they have a lower voltage and
thus cannot be used to direct drive an LED. This means that some form of circuitry, a boost circuit, is needed in between a LiFePo4 battery and the LED.

Construction of a Li-ion Battery

I'm not going into the chemistry of a li-ion battery, this is simply a explanation of what the different parts are.

So you get something like this in the mail, a protected 18650.

This protected battery is composed of a 18650 battery and a protection circuit.

(HKJ's picture)

The protection circuit placed at the negative side of the cell, but is attached to the positive side through a piece of wire. The purpose of the protection circuit is to prevent the battery from being over-discharged (discharged below 3 volts generally), over-charged (charged to above 4.2 volts), or over-current (letting out more than X amps, where X is a value generally around 6).

Then there is the battery itself.

It is composed of a number of different components stacked inside a metal casing which is then wrapped with shrink wrap. This is a before assembly picture.

That green roll is the part that actually holds the energy. It is made up of a positive electrode (a metal oxide), a negative electrode (carbon), and an insulator rolled up. All of these sit in the electrolyte (non-liquid).

Here a diagram of that is.

Now what about the other parts? Here a crappy paint diagram of the top of the battery is.

Ok, so the purpose of the insulator is to prevent the body of the cell (negative) from shorting to the top (positive). The PTC is a positive temperature coefficient. As it heats up the resistance increases, this is a kind of added protection as when the cell is shorted it will heat up. Then as the resistance increases the short will stop. The vent holes allow the battery to vent any gasses, rather than having pressure build up inside the casing of the battery.

There are 3 main types of positive contacts used on the batteries. First, and most common is flat top; these are a simple metal contact no higher than the surrounding label. This is the way batteries generally come from the manufacturer. (Does not apply to NCR18650 series) Then there is raised top, or button top, this has the same contact size as the previous one, but the whole surface is raised. This is needed in lights where the batteries are stacked to ensure contact. Then there is nipple top, this has a small raised top; much smaller. Some lights that have mechanical reverse-polarity protection require nipple tops.

People often use small round magnets to create a a nipple top from a flat top. To do this one simply places a magnet on the top of the battery, this does come with a risk. The magnet can easily slide out of space and short out the battery, it is for this reason people often place a dab of superglue under the magnet. An example of one of these magnets is this.

How to treat LiCo/LiMn Cell in Flashlights

LiCo/LiMn cells are the most dangerous kinds of Li-ion battery. They have and can explode if not treated with respect and care.

First of all, when using them in multi-cell lights make sure they are the same voltage. This means you will need to have a DMM and check the voltage before you load them in the flashlight. This is important because as they discharge if one is at 3.6 volts and the other is at 0 then the one at 0 can get reverse charged. This is how they explode.

Continuing in the mission to prevent reverse charging, one must use cells of the same capacity. This means all of the cells must be identical, and matched to each other. A few notes about this: xxxxfire cells are not considered identical and a cell that has been used a lot is not identical to an unused cell.

How to treat a LiCo/LiMn Cell When Charging

When you charge them you should always use a good charger. Do not cheap out and use a 2 dollar charger from China. Overcharging can also lead to an explosion, there are documented cases where it has.

Lico/LiMn batteries have a complicated way in which they must be charged. For this reason do not try to make your own charger. These are the directions for how Panasonic says to charge them.

As you can tell this is extremely complicated. As far as I know, there are not any chargers that follow this exactly but there are many that do do a CC/CV curve which is what matters. A CC/CV curve means that first the charger charges the battery with a constant current and lets the voltage rise. Then it switches over to constant voltage and lets the current drop. Here an example of a correct charge curve is. (HKJ)

HKJ has reviews a number of chargers so you can find one that he has approved.

My personal favorite is the Intellicharge I4 which can charge both LiMn/Lico cells and Nimh cells. It is priced very reasonably at 20-25 dollars. They also make an Intellicharge I2 which is equally capable.

Xtar also makes a number of great chargers, all of which follow a CC/CV curve.

So once you have picket out a suitable charger and need to charge your batteries you simply place them inside the charger and wait. One should stay near the batteries while they are charging, and if they start to heat up or smell unplug it immediately.

How to Treat LiFePo4 Cells in Flashlights

LiFePo4 cells are much safer than LiCo/LiMn cells, but the same rules still apply. For ease of use I repeated the information below.

First of all, when using them in multi-cell lights make sure they are the same voltage. This means you will need to have a DMM and check the voltage before you load them in the flashlight. This is important because as they discharge if one is at 3.4 volts and the other is at 0 then the one at 0 can get reverse charged. This is what often causes them to explode.

Continuing in the mission to prevent reverse charging, one must use cells of the same capacity. This means all of the cells must be identical, and matched to each other. A few notes about this: xxxxfire cells are not considered identical and a cell that has been used a lot is not identical to an unused cell.

Also, do not mix LiFePo4 cells with LiCo/LiMn cells.

How to treat a LiFePo4 Cell When Charging

Like LiCo/LiMn cells, LiFePo4 cells should be watched while in the charger.

They also have to be charged with a CC/CV curve, but the difference is they terminate at 3.6 volts.

Currently, if you want a LiFePo4 18650 charger you have to use either a hobby charger or a untested chinese charger. Neither of these is optimal.

However for 16340 LiFePo4 cells, the Xtar MP2 is capable of charging them if set to "3.0V".

One last note about LiFePo4 cells, I have personally tortured them by overcharging, shorting, overdischarging and extremely high discharge rates. Not once have they ever vented.

Estimating Remaining Capacity in Li-ion Batteries

When you measure the resting voltage of a lithium ion battery you can get a rough idea of how much capacity is left in it. Use this table.

Choosing The Right Battery

First of all, any battery that has "fire" in it's name is not suitable for use in multi-cell lights. This is because even if they may be rated at the same capacity, they are most likely not equal and could become unbalanced under high loads.

For 18650 go to post 1, for anything smaller than a 18650 go to post 2. For anything bigger go to post 3.

Feel free to comment and correct me on any mistakes.

First of all, 99% of the graphs below are from HKJ. These were done by him, I am simply placing them in this thread for easy reference.

LiCo Cells

These batteries have the highest capacities of all Li-ion batteries. They generally are rated for up to 5 amp drain. Below I have covered the most popular cells, if there are any I should add just post below.

UR18650FM

The UR18650FM is a good battery with 2600 mah capacity. It is often found in laptop battery packs. It does a much better job of keeping a high voltage than NCR18650 series batteries. For this reason it will often give longer run times than a NCR18650A if used with a 7135 driver.

Review here.

Datasheet here.

NCR18650

This battery has a high capacity (2900 mah) but is no longer very popular as the NCR18650A/B cells have a higher capacity.

Full review here.

Datasheet here.

NCR18650A

The NCR18650A is one of the highest capacity 18650s on the market with a capacity of 3100 mah. They are discharged down to 2.5 volts, rather than the 3 volts of other cells. It is often used in lights that need the highest runtime possible.

Full review here.

Datasheet here.

NCR18650B

These are currently the highest capacity 18650s made. They are discharged down to 2.5 volts, rather than the 3 volts of other cells. If you see any cell claiming to have more than 3400 mah, they are lying. Do not buy that cell.

Full review here.

The datasheet has not been released yet.

IMR-LiMn Batteries

These batteries are great for high loads.

AW IMR 2000 mah cell

Good battery, and works fairly well up to 10 amps.

Full review here.

Unknown internal cell

AW IMR 1600 mah Cell

Extremely capable battery works for loads up to and above 20 amps, albeit at the sacrifice of run time.

Full review here.

Unknown internal cell.

CGR18650CH

A hybrid IMR cell that can go up to 10 amps, and still has a good capacity (2250 mah) for IMR batteries. This is not technically a LiMn battery, but has been placed here due to it's characteristics.

Full review here.

Internal cell is CGR18650CH datasheet is here.

UR18650W

Good cell, 1500 mah capacity does very well at high loads.

(Not HKJ)

Datasheet is here.

LiFePo4 Batteries

These batteries are much safer but at the expense of capacity and voltage. For this reason they are not very popular so no full reviews have been done.

APR18650M1

This is a LiFePo4 battery, but it can deliver very high currents. It is rated to deliver 30+ amps. Very low capacity (1100 mah) Also much safer, again due to different chemistry.

Datasheet here.

Tenergy 18650P LiFePo4

This battery is a slightly weaker version of the APR18650M1, it is only rated for 11 amps despite being the same capacity.

1200 mah LiFePo4 18650

These cells are some of the most common LiFePo4 cells, they do not have a brand name or anything of that sort. They are rated for 18 amp discharges.

Example.

1500 mah LiFePo4 18650

These are higher capacity then the previous ones, but are only rated for a 4.5 amp discharge.

Example.

First of all, 99% of the graphs below are from HKJ. These were done by him, I am simply placing them in this thread for easy reference.

16340

A 16340 is a battery the same size as a CR123 battery. They are also sometimes called RCR123. As described above some are 4.2 volts fully charged while others are 3.5 fully charged. Make sure your flashlight can support the type you choose.

AW IMR 16340 (LiMn)

This battery is good for lights that need high amounts of current from a 16340.

Obviously due to the size it can only supply a maximum of 2 amps without losing a large amount of capacity.

Full review here.

Unspecified internal cell

AW 16340 750 mah Protected (LiCo)

This battery has a high capacity, but only at loads below 1 amp. In general, the IMR battery will be better.

Full review here.

Unspecified internal cell.

AW LiFePo4 500 mah 16340

These are very safe batteries, but have a much lower capacity and a lower voltage. For this reason they are not very popular.

18350

The 18350 is used in lights such as the L2M. It is 2mm thicker than a CR123 cell so it will most likely not fit in lights meant for CR123 batteries.

AW 18350 IMR

The 18350 IMR is a great battery and can handle loads up to 5 amps while still having a 700 mah capacity.

Full review here.

Unspecified internal cell.

Trustfire Protected 18350 1200 mah-LiCo

These are protected LiCo batteries, while they do have a higher capacity than the IMR version they most likely do not do as well at higher currents. No tests have been done on them so far.

14500

The 14500 is used to replace AA batteries, it has a much higher voltage than AA batteries so do not use a 14500 unless it is specified that it will work.

AW 600 mah 14500 IMR-LiMn

This battery handles loads up to 3 amps very well.

Full review here.

Unspecified internal cell.

AW 14500 750 mah-LiCo

This cell does well up until the 2 amp point, at 3 amp loads the IMR cell would most likely perform better.

Full review here.

Unspecified internal cell.

Intl-Outdoor Protected 840 mah 14500

This is the highest capacity 14500 at an approximate 800 mah capacity. Like the above battery it will do well up to the 2 amp point, but much above that and an IMR cell may be better.

Full review here.

Internal cell is UR14500P, datasheet is here.

10440

These cells are the size of a AAA battery. As is to be expected they have a higher voltage. Do not use these in your AAA light unless it is specified that it will work.

AW 10440 LiCo Unprotected 350 mah

This battery has a tiny 350 mah capacity, which is less at any significant current draw. It can only handle draws up to .5 amps.

Full review here.

Unspecified internal cell.

Efest IMR 10440 350 mah

Like all 10440 batteries it has a tiny capacity, about equal to the above one. But it can handle currents up to 2 amps.

Full review here.

Unspecified internal cell

16650/17650

The 16650 is meant to be a replacement for lights that run on 2 CR123 batteries. It has a lower voltage at 4.2 volts versus the 6 volts of the CR123s. Some lights are compatible but not all are.

Keeppower Protected LiCo 16650 2000 mah

This battery can handle currents up to 2 amps reliably, but due to the protection tripping in between 2 and 3 amps it is not as capable as it could be. It also has to be charged up to 4.3 volts to get full capacity.

Full review here.

UR16650ZT inside, datasheet is here.

Sanyo UR16650ZT LiCo 2100 mah

This battery has to be charged up to 4.3 volts for full capacity. It can only handle currents up to 3 amps.

Full review here.

Datasheet here.

Eagletac 17650 1600 mah LiCo

This battery has a lower capacity, and can only handle currents up to 2 amps.

Full review here.

Unspecified internal cell.

18500

Two of these are used to replace 3 CR123 batteries. They are thicker than CR123 batteries, but do have a similar voltage. (2*4.2=8.4; 3*3=9)

Keeppower 18500 1500 mah LiCo-Protected

This battery can handle currents up to 5 amps without a problem.

Full review here.

UR18500F inside, datasheet is here.

UR18500F 1620 mah capacity LiCo

This is the same battery used in the above battery, except it is not protected. For that reason I reused the same graph.

Full review here.

Datasheet is here.

First of all, 99% of the graphs below are from HKJ. These were done by him, I am simply placing them in this thread for easy reference.

All of the below batteries are ones bigger than 18650.

26650

These are the same diameter (approximately) as a C sized battery, and the same length as a 18650. For this reason they are often used in C maglite mods, along with in lights that want a longer runtime than a 18650.

A123 26650 2500 mah LiFePo4

This battery can supply extremely high currents but at the cost of capacity, it is rated for a 70 amp continuous discharge.

Full review here.

Datasheet here.

Keeppower 26650 4000 mah LiCo Protected

This battery can handle currents up to 7 amps, but there is variation in the batteries.

Full review here.

Unspecified internal cell.

Trustfire 26650 5000 mah LiCo Protected

This battery is one of the few good fire brand batteries. It does well up to the 5 amp load, and it would be a good idea to keep the load under that level. There is a small variation in batteries.

Full review here.

Unspecified internal cell.

King Kong ICR26650 4000 mah

This is one of the few batteries where the true capacity exceeds the marked capacity. It does well up until 10 amps, all while having over a 4000 mah capacity.

Full review here.

Unspecified internal cell.

King Kong INR26650 4000 mah

This cell also exceeds it's rated capacity, but is not as good as the ICR26650. It can handle loads up to 7 amps.

Full review here.

Unspecified internal cell.

32600

This is the exact dimension of a D cell so is a higher voltage replacement for D cells.

Ultrafire BRC32600 4000 mah LiFePo4

This cell has a lower capacity then stated, but can handle loads up to 20 amps. Due to being a LiFePo4, it does this at a low voltage.

Full review here.

Unspecified internal cell.

Feilong 32600 5000 mah LiCo

This battery has not been tested yet. One can guess that it can handle loads fairly well due to the large size, but we can't know for sure.

32650

These are slightly longer than a D cell, and higher voltage.

Feilong 32650 6000 mah LiCo

This battery has not had discharge curves done, but the capacity has been tested. It handled currents up to 13 amps.

Amp Draw

mah
1 5612
2 5580
3 5539
4 5559
5 5501
7 5404
10 5384
13 5226

Full review here.

Unspecified internal cell.

Protected LiCo 5000 mah 32650

There are no discharge curves, but at a 3 amp discharge it tested at 4697 mah to 3 volts. At a 1 amp discharge it tested at 5191 mah. This is fairly impressive.

Full review here.

Unspecified internal cell.

26500

26500 batteries are the exact size of a C battery, but they are have a higher voltage.

26500 3000 mah LiCo

This battery has not had any tests done on it, but if the specs are true is a very good battery.

Unspecified internal cell.

Hi Scaru

Another good one for the “ScaruPedia” :slight_smile:

You should probably explain what IMR (Lithium-Mangan) is as you mentioning them
and that they are considered safer (as the LiFe/Lithium-Iron) because they don tend
to start a nasty fire when they are physicaly destroyed (punctured/cut/broken).
AFAIK the Lithium reacts with Cobalt but not with Iron or Mangan.
I think not going into the chemistry is probably the wrong way as thats the essential way these cells work.

As a noob in LiIon i haven’t any experience but reading here in BLF helped a lot.

Also a mild warning about Blabla-Fire-5000mAh Cells would help not to be scammed.

Thanks for your effort

Mo

I was getting ready to PM you about this! Perfect timing…

I will add some more info about IMR batteries now, I guess I will have them be a third class.

As for not going into chemistry I am trying to keep this relatively simple. I plan on explaining that LiCo are more reactive than LiMn but I see no reason to explain why. (As that requires more knowledge and discussion of bonding etc.)

The warning about xxxxfire cells will come later on when I explain what type of batteries to buy.

I finally know what a protection circuit looks like now!

Thanks scaru. You have been a busy boy lately.

Thanks for your posts. Must say that they answer many of my questions.

Osmrs! :wink:

Great Job scaru!!! :wink:

Ditto!

An excellent resource for those getting into the addiction.

First 3 comments are lists of different types of batteries along with discharge curves. <--Still in progress

Can anyone point me towards the NCR18650B datasheet?

Double Ditto!

They haven’t been seen in public yet :frowning:

But you might try asking HKJ, he often has datasheets for cells that other people haven’t even heard of :stuck_out_tongue:

Edit: and, by the way, those FAQ threads about LEDs, Li-Ions, etc are a very nice Christmas present from you to BLF community! Thanks :slight_smile:

Ok, thanks. That's what I was guessing. I'll send him a PM.

Good job, Scaru!

The only correction I'd offer is that all ***fire cells are NOT crap. Most are, granted, especially the Ultrafire offerings, but a genuine Trustfire cell is a damned good budget cell with excellent capacity and are as safe any other good Li-Ion cell.

I have heard people say that many times, but I have never come across any trustfire cell (or any xxxxfire cell) that is equal to any other trustfire cell. For this reason they can't be used in series. At one point I had 2 that were within 60 mah of each other, but they had drastically different internal resistances. (So in high drain lights they would not be equal)

So for that reason I would say they are crap, at least for multi-celled lights. I don't see the point in ordering them, when you can buy good brand name 2600 mah cells for only a bit more.