Please explain how 18650 batteries are better?

I've heard that they greatly increase a light's performance over using 3AAA alkaline or Ni MH batteries. But in looking at the numbers, I don't understand how.

An 18650 is a 3.6Volt, 2850Mah battery from what I've looked up. No, I've never owned one, or a light that uses them (but am considering it).
3AAA also has 3.6 Volts with Ni MH, and 2700Mah if using a trio of 900Mah. Very similar again. Voltage goes up to 4.5volts if using 3 alkalines.

So where's the difference? Is it because they're lithium instead of Ni MH or alkaline?

Few things here. You cannot add both the voltage and the capacity. You either have 3x1.2v if it is in series or 3x900mah if it is in parallel, no both. Second thing here is the ability for a cell to output current. Li-ion and especially high drain li-ion has the ability to maintain it's voltage and stay cool while providing way more current.

staticx57 said:

Few things here. You cannot add both the voltage and the capacity. You either have 3x1.2v if it is in series or 3x900mah if it is in parallel, no both. Second thing here is the ability for a cell to output current. Li-ion and especially high drain li-ion has the ability to maintain it's voltage and stay cool while providing way more current.

Click to expand...

In the case of a 3AAA light, how would it be calculated? Is it still 1.2 volt even though there are 3 of them?

LEDrock said:

In the case of a 3AAA light, how would it be calculated? Is it still 1.2 volt even though there are 3 of them?

Click to expand...

Unknown, it would depend on the actual light. They could either be connected in series or in parallel. You can figure out with a multimeter with a specific light. I would suspect most use series to get the higher voltage.

Many honest 3500+ mA 18650 batteries. Being rechargeable hundreds of times is one thing that makes them "better" than primaries of any stripe. Also easier to carry a single extra 18650 instead of three AAA. Plus some 18650s can put out 30 AMPS (as noted above), about 50x what a standard AAA is rated for. That makes for a much brighter light using an 18650.

JimIslander said:

Many honest 3500+ mA 18650 batteries. Being rechargeable hundreds of times is one thing that makes them "better" than primaries of any stripe. Also easier to carry a single extra 18650 instead of three AAA. Plus some 18650s can put out 30 AMPS (as noted above), about 50x what a standard AAA is rated for. That makes for a much brighter light using an 18650.

Click to expand...

There's a light on Amazon I was looking at (actually a package of 2 that includes an 18650 battery for each) that is said to be 2200Mah. Here it is: https://www.amazon.com/gp/product/B07XJN27NZ/?tag=cpf0b6-20

LEDrock said:

In the case of a 3AAA light, how would it be calculated? Is it still 1.2 volt even though there are 3 of them?

Click to expand...

It's probably series since most leds need more than ~1.5 volts to turn on. The 18650 battery is in laptops and a LOT of other consumer electronics. It's HEAVILY researched and improved, the aaa nimh, not so much. Now the aa nimh is different... it's optimized much moreso than aaa, but even it appears to have hit its limit.

Also, and this is not so much 18650 specifically, but li-ion cells have a VERY low self discharge... like <5% a YEAR. Nimh is like 30% a MONTH.

turbodog said:

It's probably series since most leds need more than ~1.5 volts to turn on. The 18650 battery is in laptops and a LOT of other consumer electronics. It's HEAVILY researched and improved, the aaa nimh, not so much. Now the aa nimh is different... it's optimized much moreso than aaa, but even it appears to have hit its limit.

Also, and this is not so much 18650 specifically, but li-ion cells have a VERY low self discharge... like <5% a YEAR. Nimh is like 30% a MONTH.

Click to expand...

I see what you mean about the AAA Nimh not being improved so much. I have some 600Mah AAA cells and I tried using them in a Lumintop 1AAA light I just bought, and the light only runs for a couple minutes in low mode before shutting off. So I have to use it with alkalines or it won't even work.

LEDrock said:

In the case of a 3AAA light, how would it be calculated? Is it still 1.2 volt even though there are 3 of them?

Click to expand...

Flashlights using 3xAAA batteries usually combine those three individual cells in series. To calculate batteries in series you add the voltages together by the number of cells (1.2vx3) but the capacity or mAh of the cells is not added but remains the same. (Note in a parallel configuration it would be opposite with the capacity being added together but the voltage remaining the same) In the case of flashlight with 3xNIMH AAA cells you would end up with a three cell pack with a voltage of 3.6v @ ~800mAh. To calculate the total power contained in that pack you would multiply volts times mAh and get: 2.8 Watt hours of total power the batteries could provide.

A high capacity 18650 lithium cell has a nominal voltage of 3.7v and a capacity of as much as 3500mAh for a total power capacity of 12.95 watt hours or over four and a half time more capacity the a 3xAAA cell pack.

And as mentioned before, an 18650 battery can also provide more output to run an LED with more current giving you a much brighter light.

In short an 18650 battery is better because it can give you a much brighter light that can run for up to four times longer than a similar 3xAAA powered flashlight and the size of the light may only be slightly longer depending on the configuration of the 3xAAA pack.

filibuster said:

Flashlights using 3xAAA batteries usually combine those three individual cells in series. To calculate batteries in series you add the voltages together by the number of cells (1.2vx3) but the capacity or mAh of the cells is not added but remains the same. (Note in a parallel configuration it would be opposite with the capacity being added together but the voltage remaining the same) In the case of flashlight with 3xNIMH AAA cells you would end up with a three cell pack with a voltage of 3.6v @ ~800mAh. To calculate the total power contained in that pack you would multiply volts times mAh and get: 2.8 Watt hours of total power the batteries could provide.

A high capacity 18650 lithium cell has a nominal voltage of 3.7v and a capacity of as much as 3500mAh for a total power capacity of 12.95 watt hours or over four and a half time more capacity the a 3xAAA cell pack.

And as mentioned before, an 18650 battery can also provide more output to run an LED with more current giving you a much brighter light.

In short an 18650 battery is better because it can give you a much brighter light that can run for up to four times longer than a similar 3xAAA powered flashlight and the size of the light may only be slightly longer depending on the configuration of the 3xAAA pack.

Click to expand...

Thank you for explaining this. It gives me something to think about. The prices for those 18650 batteries are pretty steep, especially when factoring in the advice I've gotten about getting the quality ones instead of the cheap ones.

LEDrock said:

Thank you for explaining this. It gives me something to think about. The prices for those 18650 batteries are pretty steep, especially when factoring in the advice I've gotten about getting the quality ones instead of the cheap ones.

Click to expand...

Yes. Probably the biggest downside to li-ion cells is the safety/handing issue. They are not really for 'casual' light users. There are plenty of really good/bright lights that run really well from AA nimh cells.

The light you buy REALLY NEEDS to have discharge protection built into it so it doesn't damage the battery if using li-ion.

One other thing that many don't tell you about is when you run 3AAA in series if the cells aren't nearly identical in capacity and internal resistance you can have cells drain to nothing while some still have some juice left in them and a device that can operate below 3v you can see the batteries that still have juice left in them holding their voltage and the spent ones dropping to 0, then even reverse charged (to negative voltage) which damages them. I've had too many nimh batteries in series end up with damaged cells. The weakest cell in a series group determines the runtime at full output because when it depletes the voltage in it drops and brings down the output of the device with it.
An 18650 is a single cell and doesn't suffer with the series nimh cell problem. You can get 3500mah cells for decent prices and they are light and can be charged hundreds of times plus you can get chargers that hold 4 of them while trying to wrangle a dozen AAA nimh cells and keep them in groups that are matched while charging them is a nightmare.
I've pretty much dropped as many 2-4 AA/AAA lights I have and replaced them with single cell lights or multiple 18650 in parallel.
The best 3AAA light is lucky to do 500 lumens for long while 18650 lights can do 1000+ lumens or 500 for a pretty long time.
Another thing that sucks about 3 cell lights is most have the drop in cartridges that you have 2 facing one way and a third facing the other. It is almost impossible to change batteries without a light and sometimes with nimh you need a screwdriver to pop one out. A single 18650 you can change it in the dark by feeling it.

I use 3600mAh Orbtronic in my radios (Tecsun PL-990 and PL-110s (two of them)). If playing just the radio, they last forever.

5S8Zh5 said:

I use 3600mAh Orbtronic in my radios (Tecsun PL-990 and PL-110s (two of them)). If playing just the radio, they last forever.

Click to expand...

Unless you have a high performance (audio output) radio, batteries can last a very very long time. I have a AAA battery in a cheap radio that uses headphones only that runs for about 20 hours on a nimh cell, and have a 2AA WD40 can radio that runs about the same length with a cheap sounding speaker. Radios using C/D cells can run for many days, even weeks perhaps if you don't turn them up overly loud. I have a 4C table radio from the 70s that I have not changed the batteries in decades that has gone through several power outages that still
has plenty of power. I've had to swap out a leaking cell on occasion but they way the battery tray is made leaks aren't an issue with this radio easy to clean up the mess they make.

If your flashlight can support it, it's the current that 18650 can put out. Some triples or other similar lights can draw 15 amps or more

+


energy density
amps supported
weight
charging 1, not 3
overall simplicity
amps supported
likely a few more things I forgot

yes, amps supported

One other thing is you can harvest cells from many devices if you have a need for cheap batteries. Tools and power banks and old laptop batteries have 18650s in them. I bought a power bank for $10 awhile back that has 5 3350 Panasonic 18650s in it and got a bad tool battery with 5 1300mah 18650s of which two were bad 3 were good.

LEDrock said:

Thank you for explaining this. It gives me something to think about. The prices for those 18650 batteries are pretty steep, especially when factoring in the advice I've gotten about getting the quality ones instead of the cheap ones.

Click to expand...

The price of a quality 18650 cell should be comparable to the price of 3xAAA Eneloops. This may vary, depending on where you can order from, but the prices should be comparable, especially if we are talking about unprotected cells. So, for roughly the same price you are getting 3 times the capacity (or more) at equal voltage, or 3 times the voltage at the same capacity, depending on how the AAA cells are connected.
No brainer IMO.

dont forget the wasted space of a 3 aaa carrier.
its like those blocks that restrict flush volume of a toilet.
you are replacing the wasted space with active material be it battery plates or water.
also reliability goes up with one cell with 2 contacts vs 3 with six.

NiOOH said:

The price of a quality 18650 cell should be comparable to the price of 3xAAA Eneloops. This may vary, depending on where you can order from, but the prices should be comparable, especially if we are talking about unprotected cells. So, for roughly the same price you are getting 3 times the capacity (or more) at equal voltage, or 3 times the voltage at the same capacity, depending on how the AAA cells are connected.
No brainer IMO.

Click to expand...

Actually the highest capacity Eneloops are around 2500mah where the highest capacity 18650 is about 3500mah so you are getting an extra 1000mah capacity or MORE than an extra Eneloop of power or about 120% of an Eneloop more. I guess you could say 4.2 Eneloops in a 3500mah 18650. If you use the more rugged lower capacity Eneloops (2000mah) you get 5.25 of them in an 3500mah 18650.
If you were to compare even 3 Eneloops in a light vs a single 18650 there is a big difference in size especially if the cells are in a cartridge (side by side) format.