18650/19670 are rechargeable lithium ion batteries commonly found in home appliances, high-end toys, laptops and similar devices that require light and powerful source of electricity. They are even often used in electric and hybrid cars.

Note: 19670 is the 18650 battery, but with electronic circuitry for protection against over-charging, over-discharging, high temperature and others factors that can shorten lifespan of lithium ion batteries or even cause them to overheat and catch fire. So, when a battery is described as '19670 battery', that is actually 'protected 18650 battery' and, of course, vice versa.

Physical Dimensions and Weight

Physical dimensions of 18650 batteries are (diameter x length) 18.6 × 65.2 mm (0.73 x 2.56 inches). These dimensions differ slightly from model to model. Some 19670 batteries are almost 68-69mm long due to added circuitry (to avoid loss in capacity), while some models have standard length of 65mm with slight loss of capacity.

For example, ORBTRONIC 3400mAh protected 18650 batteries use excellent Panasonic NCR18650B cells with added protection, which increases the length of the battery to 68.9 mm (+/- 0.03) - basic data for the both batteries are given in the table at the end of the article.

18650 batteries on average weigh around 45-48g, although models with higher capacities weigh up to 55g or even slightly more.

18650 battery flat vs button top

Do I need 'flat' or 'button' type 18650 batteries? Some batteries come with flat top side (positive), while some models come with button top side. Before purchasing new batteries, be sure to check your old batteries. Photo above shows two different types of 18650 batteries - on the left is positive (top) side of 'flat top' battery and on the right site is positive (top) side of 'button top' battery.

Some 18650 batteries come with soldering tabs - when soldering tabs are removed, such batteries can be used (in most cases) as common flat top batteries. But, if one needs to make a custom battery pack, batteries with soldering tabs are way to go. In most cases, such batteries are made to be robust and to tolerate physical and electrical 'abuse' on a daily basis.

However, if you are not experienced in working with these batteries and soldering in general, find a professional to do it for you (and no, we don't offer that kind of service).

Capacity and Protection

Maximum capacities of these batteries is around 3-4 Ah, although there are batteries with higher capacities, but that often comes with higher price, lower maximum allowed discharge current, lower number of charging/discharging cycles and similar. When used in cordless vacuum cleaners, their capacity is usually around 2-2.5 Ah (2000 - 2500 mAh), but such batteries can tolerate punishment on a daily basis with higher discharging currents.

Due to additional electronic circuitry, 19670 batteries ('protected 18650') have lower capacity than common (unprotected) 18650 batteries and it ranges usually around 2.5-3.5 Ah, rarely more. But such batteries are much safer than 18650 batteries, which must be protected by external circuitry. When replacing old 18650/19670 batteries in your cordless vacuum cleaner, be sure to buy exactly the same batteries - same model (18650 or 19670) and same or higher capacity and same or higher maximum allowed discharging current.

19670 (protected 18650) typical protection activation levels vary from model to model, but generally protection is activated at:

- Over-current - activated when discharging or charging currents reach 5 to 10 Amps, sometimes even more; discharging and charging over-current levels are not always the same,
- Over-charge - activated when cell voltage reaches 4.35V,
- Over-discharge - activated when cell voltage drops at 2.5V,
- Over-temperature - activated when cell temperature reaches temperatures between 70 and 90°C (between 158 and 194°F), depending on the manufacturer and battery internal construction.

Battery Nominal Voltage and Internal Construction

18650 batteries are lithium ion batteries with their voltage being around 3.6 - 3.7V and which gives them much higher energy density when compared with NiMH batteries.

Voltage difference is due to lithium ion battery construction - the most popular negative electrode in commercial batteries is graphite, water-less electrolytes use various organic carbonates and salts containing lithium, while positive electrode is generally made out of one of these materials:

- a layered oxide (such as lithium cobalt oxide or lithium manganese oxide),
- a polyanion (type of polymer),
- a spinel (type of mineral).

For most of the users, lithium ion construction is not so important, but one has to know that their voltage differ slightly and if you see lithium ion battery with 3.6 or 3.7V, it is practically the same battery type, but made using slightly different materials.

Maximum discharge currents of typical 18650 batteries are around 10-15C (25-50 Amps), even more in short bursts.

18650 and 19670 batteries cost more when compared with similar NiMH and especially NiCd batteries, but they store more energy per mass and volume of the battery. Due to their characteristics, 18650 batteries are often used in various devices and appliances ranging from flash lights, laptops, power tools, R/C toys, home appliances like cordless vacuums to various electric vehicles like golf carts and electric and hybrid cars. Since lithium batteries don't use cadmium, mercury and similar materials, they are much more environment friendly than NiCd and lead acid batteries.

Lithium batteries also have few, very important flaws: they require high quality chargers and they cost more then NiMH and NiCd batteries.

18650 Battery Packs

18650 batteries are commonly used connected in series, with voltages depending on number of used batteries:

18650 samsung 25r - two 18650 cells in series provide 7.2V,
- three 18650 cells in series provide 11.1V,
- four 18650 cells in series provide 14.4V,
- five 18650 cells in series provide 18.5V,
- six 18650 cells in series provide 22.2V,
- seven 18650 cells in series provide 25.9V,
- eight 18650 cells in series provide 29.6V etc.

18650 batteries are not used connected in parallel, at least not without special protective electronics. 19670 batteries can, in theory, be connected in parallel to create a battery pack with higher capacity, BUT ONLY IF that is declared officially by their manufacturer. Reason? Protective electronics differ greatly, some provide most basic protection, while some models provide high degree of protection, including connecting lithium battery cells in parallel. Anyway, I haven't yet heard of a cordless vacuum cleaner using lithium batteries connected in parallel.

One of the reasons why manufacturers of home appliances like vacuum cleaners increase voltage of battery packs is that higher voltage enables transfer of more energy over the same wires with less energy loss due to electrical resistance in wires. For example, if vacuum cleaner requires 100W motor, 11.1V battery would have to provide 9 Amps, while 22.2V battery would have to provide 4.5 Amps of current.

There are also other benefits of using higher voltages battery packs in such devices (it would be very hard to explain those benefits without too much physics, chemistry, math ...).

How to Choose the Best 18650 Battery?

Choosing the best 18650 battery should not be a daunting task - choose according to your device and usage needs. For example:

- high drain devices require batteries able to provide large currents. So, before buying new batteries, check maximum current drain of the device and go for batteries which can provide such current with ease - 10 Amp device will never push over the limit 20-25 Amp batteries.

- low drain devices don't require batteries with huge maximum current, but they will operate longer with the high capacity batteries. In such devices, 2500 mAh 18650 battery with 35 Amp of maximum current will not perform as good as 5000 mAh 18650 battery with 5 Amp allowed maximum current.

- standby devices (emergency cordless vacuums, for example) must operate at full power when required, but they can be used every few days, weeks or even months. Such devices require batteries with low self-discharge rate and both good capacity and good maximum allowed current.

- devices with no protective electronics require protected 18650 batteries - 19670 batteries. Built-in protection of 19670 batteries will prevent overheating, overcharging, over-discharging and other 'overs', which can damage the battery or device and cause battery to catch fire or even explode. 18650 batteries with such protection tend to cost slightly more and have smaller capacity, but such protection is, IMHO, worth it.

As you can see, it is very easy to pick right 18650 battery for every task :)

Most popular manufacturers and their models of 18650 batteries are given in the following table:

Photo Manufacturer Model  Capacity Max Current Amazon link
clearance 18650 battery Clearance - 5800 mAh - Clearance 18650 Battery
foxnovo icr18650 3100 t Foxnovo ICR18650
3100 mAh - ICR18650 3100mAh
foxnovo icr18650 t Foxnovo ICR18650
3400 mAh - ICR18650 3400mAh
lg18650he2 LG


2500 mAh 35 A LG18650HE2
 lg chem 18650he4 t LG LG18650HE4 2500 mAh 30 A LG18650HE4
orbtronic 3400mah t Orbtronic
(Panasonic Cell)
3400 mAh 10-12 A Protected NCR18650B
panasonic ncr18650b t Panasonic NCR18650B 3400 mAh - NCR18650B
18650 samsung 25r t Samsung


2500 mAh 35 A INR18650-25R
 sony us18650vtc4 t Sony US18650VTC4  2100 mAh 30 A US18650VTC4
 tenergy 18650 tabs t Tenergy B001JDPHG4
2600 mAh - B001JDPHG4

This table could be longer, but although there are other good 18650 batteries around, batteries in the table have very good ratings from real life users.

Note: when buying batteries (and not only batteries), read the reviews and check average ratings since there are many FAKE batteries around. For example - simplified - if the batteries have three star rating because 20 users have said those batteries are fake and 20 users have said they are good, I would stay away from such batteries. On the other hand, if a battery has 4.5 stars rating because 300 users have said so, I believe that battery is genuine one :)

Good luck and be very careful with lithium batteries - they are great and they store large amount of energy in light, small packages.


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