Please explain pros/cons of IMR versus standard Li-Ion rechargeables

I’m looking for an explanation of the pros and cons of IMR batteries compared with standard Li-Ion batteries.
I see a lot of mention of IMRs but I don’t have a clue as to whether I should be using them…

For example I’ve been using standard unprotected NCR 18650Bs in my single cell flashlights (eg.DQG Tiny 18650) with the expectation that these will give me the longest run-times and are safe (charged with a reasonable quality charger like the nitecore intellicharger I2).
Are IMRs good/better for this purpose or only for high-drain high lumen flashlights?

I also want to get some 14500s and 10440s for other flashlights and wonder if I should be buying Li-Ion or IMRs there too?
Thanks in advance for any advice you can offer…!

IMR cells have lower internal resistance and can support higher drain rates(more current) but have lower overall capacity. Trying to run non IMR cells at high current is more dangerous and counterproductive. An over amped cell can overheat and even if it doesn’t the high internal resistance will cause a voltage drop that won’t support the higher Vf that occurs at high current. More of the cells stored energy goes into heating the cell instead of pushing the led and the extra capacity isn’t realized in lumens over time.

Probably all wrong but that’s my understanding of it.

IMR cells are required for high drain applications. The obvious question is what constitutes high drain. I consider the upper limit for ICR cells to be about 3.5 amps. If your intended use is going to exceed 3.5 amps, you probably should be looking at either a hybrid cell, or an IMR cell. Most hybrid cells such as the Panasonic 18650BD has capacity more in line with ICR cells, but substantially higher current capability. The Panasonic 18650BD cell is supposed to be good for up to 10 amps. The true IMR cells can be good for much higher currents, and are usually found in applications such as battery powered drills, saws, etc. Some of the IMR cells are good for about 30 amps maximum current. My personal view is that if you are going to consistently draw more than about 6 amps, you probably should be using IMR cells, rather than Hybrid cells. The standard ICR cell protection (if equipped) will trip well before 6 amps, and without protection, the voltage sag on a standard ICR cells will be so large that the light probably won’t be able to run ‘in regulation’ let alone full output.

Because the IMR cells have such low internal resistance, they in general are not subject to catastrophic thermal ‘runaway’, which can happen to unprotected ICR cells under very heavy loads. The Internal heating of the battery is proportional to the current squared. So going from 1 amp to 3 amps increases the internal I^2 x R losses by a factor of 9. The bad news is that ICR cells generally have substantially less capacity than the ICR cells. As a result, in applications where the current is relatively low, the ICR cells give substantially longer run time. In somewhat heavy duty applications, the Hybrid cells perform better than ICR cells, and have capacity close to ICR cells (and still well above IMR cell capacity).

As to which cell you should be using, At this point, a single 18650 ICR cells should support output up to about 1000 lumensin current designs (XM-L2 or XP-L LED’s). Any application that produces more than about 1000 lumens per cell in the battery pack will be better off with a Hybrid cell, or an IMR cell if run time isn’t an issue. For example a standard ICR cell cannot delivery full output is high powered flashlight like an Acebeam K60, which has a maximum output of about 5000 lumens (1250 lumens per cell in the battery pack). IIRC correctly, the maximum output from a K60 is achieved with IMR cells, although the difference between IMR and Hybrid cells in output is quite small.

Typical ICR capacity these days is 3300-3600mAh,
Hybrid Capacity is about 3200mAh
IMR Capacity is typically about 2600mAh

HKJ’s reviews of batteries show the actual energy that each type of cell can deliver under various loads and is a useful tool in figuring out which battery is best for which application.


Well explained, but I would argue that in most applications an imr will beat an ICR. Take a look at the Samsung 25r vs the 26f. Same capacity (almost) and for abouut the first half of its capavity, holds its voltage better as low as 1amp. Also capacity is not significantly lower anymore, you can get 3 amp now in imr

It’s an interesting question and subject though.


Its a very, very, interesting subject. Would be great if more of the experienced people on this forum waded in with their opinions :slight_smile:

How do I estimate current from IMR cells used with FET drivers at 100%/PWM=255? Looking at some graphs\_~~DoOtWs/s800/XML-2%2520vF.jpg / max draw from a freshly charged (IMR) cell~~ or two for 6V emitters i.e. 8.4V - seems like it would slightly exceed sustainable levels.

A big advantage is charging with high currents without damaging the the cells. Some cells will take even 4A but generally they will take 2.5A. While in the flahshaholic world this feature is ignored I believe this is very important as with time we want faster charging of cells (why not faster charge today?).

This is important for power tools of course.


OK thanks for all your responses!
Whilst the technical arguments are way beyond me, the consensus seems to be that “standard” Li-Ion cells are still the go-to for powering basic single cell LED flashlights below 1000 lumens.

As mentioned I’m using NCR18650Bs in my single-cell DQG (and also my WF-510B/XML2/1.4A).
Unprotected seems fine to me for this purpose…

Can you recommend equivalent relatively high capacity/quality 14500 and 10440 non IMR cells?

Find the cell (if he’s tested it) in HKJ’s reviews

Get the next-to-last graph he shows which is a Current Sweep of the cell

Find a Vf plot of an LED like the one’s you linked

Then in Powerpoint or whatever paste both images

Set the background of one plot transparent by going to Format>Color>Set transparent color

then rescale the images so the current and voltage grids line up

and observe the point that the lines cross

this will be fairly close to your direct drive current


Here’s an example

This suggests a new and fully charged Sanyo 2600 would pull ~5.4A into an XML2 with similar Vf


Another example with a well known high current cell, the LG HE2. This method, with an exptrapolation of the Vf curve, suggest ~6.7A for this cell

Sanyo UR14500P don’t know about non-IMR 10440’s since I only use Efest cells in that size.

If you want a protected 14500, Keeppower do a good one!

14500 is a different matter since the question becomes are you going to run it in a light that also takes a AA battery ...because if you are then you want to always run a protected cell..?OR pay really close attention to the voltage because letting it go below 2.5 is not really healthy for batteries and when they run down to 1.2V or a volt you've definatly hurt your cell . So the answer is a little of both is what you want and a bit of care works well too.

again I really could care a less about protection on a battery if it isn't needed . for 18650's i use 90% new unused OEM japanese / korean laptop pulls ...7%LMR and 3% protected .

Most of my protected cells are 14500's

most 10440's aren't protected just use a efest LMR

* 14500 Keepower protected can be too fat for some lights . Some are either double wrapped or out of spec ?. I still like and use trustfire flames in lots of 14500/ AA lights.Sanyo cells are exactly whats in all the higher $ brand name batteries so buy them in a red wrapper instead of paying for someones name to be added to them.

I am looking to replace an existing 18350 lithium ion battery in a Sangean rechargeable radio - not in a flashlight like most of the references here. Would I be better off with an IMR or lithium-ion replacement?

You know IMR is one of a few possible Li-Ion chemistries?

Chemistry, performance, cost and safety characteristics vary across LIB types.

Handheld electronics mostly use lithium polymer batteries (with a polymer gel as electrolyte) with lithium cobalt oxide (LiCoO2) as cathode material,
which offers high energy density, but presents safety risks, especially when damaged.

Lithium iron phosphate (LiFePO4),

Lithium ion manganese oxide battery (LiMn2O4, Li2MnO3, or LMO), and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC) offer lower energy density but longer lives and less likelihood of fire or explosion.
Such batteries are widely used for electric tools, medical equipment, and other roles. NMC in particular is a leading contender for automotive applications.
IMR are lithium manganese rechargeable,
INR are lithium nickel rechargeable
ICR Nickel/cobalt/dioxide
NCR Nickel/cobalt/dioxide (Panasonic)

Then also cells with shell and ones without are to discuss both have their advantage

Modern batteries are mostly hybrid types to reach improved specs
HKJ uses this simple 3 types

ICR are the usual type of LiIon batteries.
IMR has less capacity and can deliver higher current.
IFR is a lower voltage.

Given this, which would be better for a rechargeable radio application: IMR or lithium-ion?

IMR is a li-ion chemistry.

That’s like asking if a Camry or sedan is better.

I would go with whatever the manufacturer uses unless you’re building your own external power supply for a big portable HAM setup. If the latter, you’ll need to really know the electrical requirements of what you’re powering and almost certainly some sort of controller/regulator. Probably better off with a pre-built power supply at that point.

That’s like asking if I should buy a Sedan or Chevrolet

It's like asking myself if it is nascent sp#m.

But, I got to see Scott's signature that I like, that I have recently been wondering where it/he went. :)

Quote: "Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?


Totally missed that you mentioned earlier it was a handheld using an 18350, sorry!
I would just measure the cell, if it is much more than 35mm long and/or 18mm wide you will want a protected 18350. If it’s almost perfectly 18x35mm any unprotected one will do fine.
You need to consider whether it is button or flat top as well. If button add 2-3mm to the potential length of either pro/unpro. You will want a replacement that is the same (button vs flat) as the original to make sure it makes contact.

But yeah, basically any modern li-ion cell that is 3.7V will do the job of another except in very high drain applications (like hotrod flashlights or e-cigs). Just look at “mAh” for capacity and “max continuous drain” for the amperage it can safely maintain. In a handheld radio you shouldn’t have to worry a bout high-drain AFAIK.