The 18650 is one of the most popular lithium-ion battery out there. While once reserved for device manufacturers, they’ve now become available to consumers and DIY enthusiasts and loving them.
While they may look a lot like the AA or AAA cells that we’re used to seeing, they’re far from being standardized in that fashion. 18650 cells come in various capacities and ratings that can make picking the right cell a daunting choice if you don’t know what you’re doing.
What are 18650 cells?
As the name suggests, these batteries are cells that are 18mm x 65mm in size. These cells offer the performance of a lithium-ion cell in capacities ranging from 1800 to 3500 mAh. You can find them in a lot of devices from laptop batteries to cellphones and everything in between,
They offer perhaps the best performance of just about any consumer-grade rechargeable battery, but they’re not standardized. Different batteries come in at different capacities and continuous discharge rates, otherwise known as CDR and measures in amps (A).
Also read: Top 7 20,000mAh power banks
How to pick the right cell?
When picking a 18650 cell, make sure to note how much power your project will draw and what capacity cells you’d need to power the whole thing.
It would help if you ensured that the battery’s CDR is more than your project’s current draw. If it isn’t, your cells can overheat, damaging their lifespan. Overheating can also cause these cells to leak and, in some cases, explode.
There’s a relation between a cell’s CDR, and it’s capacity. The higher the capacity, the lower and CDR and vice-versa. This means that while low powered devices can enjoy high capacity cells, devices that draw more power will require lower capacity cells to draw power safely.
If you’re looking to make a battery out of these cells, you should also consider whether your cells are protected or unprotected and whether or not they have a flat top or a button top.
Protected vs unprotected cells
As the name suggests, protected cells have circuitry built inside them that protects the cells against extreme current draw, overheating, discharging beyond the end voltage, short-circuiting and excessive charging.
The additional circuitry also means that these cells cost more. If you’re looking to make a battery pack out of these cells, you can get away with using unprotected cells and then slapping a protection circuit on your battery. Still, otherwise, we suggest spending the extra money and getting protected cells.
Flat top vs Button top
Another difference between a lot of 18650 cells is that they’re either flat-top or button-top. This pertains to the positive end of the battery.
Flat-top cells sit perfectly flush on the positive end, while button-top cells have a raised metal plate on top. While it isn’t a huge difference, picking the wrong battery can leave you trying to squeeze a cell somewhere with no space.
How to avoid fake cells?
Just like everything else brands cells, there are 18650 fakes out there as well. And make no mistakes. These fakes are near indistinguishable from the real ones. The only difference that can tell for sure whether or not a cell is real is its weight.
When you’re trying to verify the integrity of a cell, look up its datasheet. It should have the cell’s weight mentioned somewhere. Fake cells are more often than not lighter than their authentic counterparts.
Not only buying a fake battery is a total waste of your money, but it can also be unsafe in case the battery’s rating is falsely marked. Aforementioned, if the CDR is lower than the device’s current draw, all sorts of bad things can happen.
Top 7 18650 cells
Here are the top seven 18650 cells of varying capacities that you can buy online.
Samsung 25 R
Manufacturer: Samsung | CDR/Capacity: 20A/2500mAh | Price: $4.99/cell
This cell from Samsung is perhaps the most popular 18650 cell out there. You can find it in just about anything that uses lithium-ion cells, including many laptop batteries.
Manufacturer: Molicel | CDR/Capacity: 35A/2600mAh | Price: $4.99/cell
This is one of the newer cells released by Molicel and offers you amazing value for the price. With its high CDR, the cell is perfect if you’re looking for batteries to run a high-powered project or device
Manufacturer: Murata (formerly Sony) | CDR/Capacity: 25A/2600mAh | Price: $6.99/cell
This is an extremely reliable and safe high CDR cell thanks to its Nickle Magnesium Cobalt (NMC) chemistry type, which allows the cell to maintain safe temperatures while sustaining high discharge rates.
DLG 18650 battery
Manufacturer: DLG | CDR/Capacity: 7.8A/2600mAh | Price: $1.99/cell
These generic inexpensive cells from DLG are a great option for pack builds with their matching voltages and Grade A certification. If you’re looking to make a battery pack out of 18650 cells, this should be your pick.
Manufacturer: Sanyo | CDR/Capacity: 10A/3500mAh | Price: $4.99/cell
This is a great cell for building battery packs, Battery Management Systems (BMSs), power banks and is even recommended for use in high powered flashlights. It’s also commonly used in e-bikes and other electric vehicles as well.
Manufacturer: Panasonic | CDR/Capacity: 4.9A/3400mAh | Price: $4.99/cell
This is an unprotected 18650 cells from Panasonic that’ll fit the bill for any project with a not so high current draw but high battery capacity requirements. The cell is a popular component of power banks, BMSs and other smaller devices.
Hohm Tech Life V4
Manufacturer: Hohm | CDR/Capacity: 22.1A/3015mAh | Price: $7.99/cell
The cell is designed to feed power-hungry devices without either swapping or charging the cells very frequently. The high CDR and capacity combination makes it a wonderful choice for just about any high power project.