Are all 18650 Batteries the same?

The ultimate guide to understanding differences in 18650 batteries.

The short answer is – No. The long answer? Read on…

18650 batteries have just a few things in common. They will all be roughly 18mm in diameter, 65mm in length and will all have a positive and negative end, an insulator disc and an outer wrap. This is where in appearance at least, the similarities between all 18650 batteries end.

Let’s start with the primary differences;

Nominal Voltage – There are 3 primary nominal voltages used in 18650 batteries. 3.2V, 3.6V and 3.7V. The 3.2V nominal voltage is exclusively for LiFePO4 (also known as Lithium Iron Phosphate/IFR) chemistry. The most commonly used/available now are 3.6 and 3.7V.

Capacity – One of the most important characteristics in any battery is the amount of energy it holds and how long it can expend that energy for, measured in Ah (Amp hours) or mAh (milliamp hours). Capacities can range anywhere from sub 1000mAh (1Ah) to as much as 3500mAh (3.5Ah) like the LG MJ1. Capacity is also sometimes expressed as “Energy Density”. This comes in three forms – Simple Watt hours (Wh) based on capacity in Ah or mAh multiplied by voltage and then divided by 1000. Volumetric Energy Density (written as Wh/l, giving a figure of Watt hours per litre of active material) or Gravimetric Energy Density (written as Wh/kg and as a measure of Watt hours per kg of active material)

Discharge rating – This is the maximum amount of current the battery can provide continuously down to the low voltage limit, measured in Amps. You can normally find this on the factory data sheet for the cell/battery. A quick search of Google might get you this in .pdf form or you can pop us an email through the contact form and we’ll gladly email it back to you.

Internal Resistance or “impedance” – Measured in Ohms or milliohms, this is the factor which determines how easily or “fast” a battery can expend its energy. A high IR battery will expend its energy much more slowly than a low IR battery. Generally, the higher the maximum discharge rating of the battery (and therefore the lower capacity), the lower the IR will be, for example the Sanyo NCR18650B (6.7A) has a factory stated IR of <100mΩ, while the Sony VTC5A (25A) datasheet shows an acceptable range of 7-15mΩ (measured AC 1kHz).

Wrap colour – This is actually of little consequence. Sony/Murata use Green on all of their current products, Sanyo are now almost exclusively using red, Panasonic are a light green with black stripes, Molicel are all grey and Samsung use lots of different colours with the theory that this was based on capacity bands however this no longer appears to be the case. LG also use lots of different colours. That’s not to say however that all Red batteries are Sanyo and all green are Sony. We’re just highlighting this as a difference here.

Chemistry – All 18650 cells contain Lithium (Li) in varying amounts, but it’s the other components in the chemistry (and also in their varying amounts/blends) that determine the capabilities of the battery in terms of capacity and discharge rating.

Here is a breakdown of the most commonly available and used battery chemistries;

  • IMR – Lithium Manganese

    IMR is one of the most stable and one of the highest current producing chemistries. It has the lowest running temperature in comparable tests making it far safer than older ICR technology. Interestingly, a lot of re-wrap companies mark their batteries IMR, when they’re actually INR.

  • INR – Lithium Manganese Nickel

    INR is probably the most common in vaping. It blends nickel and manganese to form the positive cathode, providing low resistance and the ability for high current output. A lot of effort is put into this chemistry by manufacturers, shown in the Samsung 25R and the LG HE2.

  • NCA – Lithium Aluminium

    NCA is a much lesser used but still comparable chemistry to INR. It does away with the manganese element of the cathode in favour of aluminium. You wont get the high level discharge ability of an INR cell, but you do get a much longer run time and increase shock resistance. They’re currently being used by lots of e-bike manufacturers, and Tesla use them in their vehicles!

  • ICR – Lithium Cobalt

    ICR chemistry is used for one purpose. Energy density. Unfortunately this comes at a cost and that cost is stability. It bugs me that cells with this internal chemistry are available individually to end users on eBay and Amazon because they’re of almost no use to the general public bar DIY pack repairers. The Samsung 26F for example (most often found in laptop batteries) has a wrap the same colour as the Samsung 30Q; they can be very easy to confuse. The 26F is a 5.2A cell (factory data sheet rating) which is of almost no use in vaping. Put one of these in a vape device and run it at above 20w and you’re almost guaranteed to have a bad time.

  • IFR – Lithium Phosphate

    IFR (more commonly known as LiFePo4) has very specific uses and is rarely seen now du to advances in other chemistries. There are some that can be discharged at very high rates however, often up to 30C (30x its capacity) The average capacity is about 1200 mAh, some are much lower. For example a 30C rated IFR cell could be discharged at 30 x 1100mAh, that’s 33Amps! But, it wont do it for very long at all. They also have a low voltage cut off of only 3.2v. Much higher than the normal 2.8v or even 2.5v of other lithium based cells.

Button top or Flat top?

All batteries manufactured by the large OE manufacturers (Samsung, LG, Sony, Panasonic/Sanyo, etc) are manufactured in flat top form. This is because they’re industrial cells which were never intended to be used by consumers outside of the often larger, fully assembled battery packs they were designed for. These can be anything from just one battery inside a portable radio or toothbrush, to several thousand or more used inside electric vehicles. For the most part, we supply them exactly as they came from the supplier, apart from our compliance marking process. Recently, more and more devices are appearing on the market which require an 18650 battery but with a button top. The now extremely popular Chinese manufactured Video Doorbells are a prime example. In all cases, these are added post production. At 18650.UK, they are spot welded onto the battery to ensure a long lasting, solid and electrically sound connection. Some are simply self adhesive with a clear overwrap to hold them in place. Our advice – steer clear of these.

Protected or Unprotected?

This is another non-factory standard add-on 18650/lithium rechargeable batteries are unlike NiCd/NiMh batteries in that they have a low voltage limit, normally between 2.5 and 2.8V. It’s important not to discharge them below this level or to 0.0V because it can cause irreparable damage to the chemistry and therefore their performance. Often, manufacturers of smaller items like torches and lasers will leave out any kind of over-discharge protection because this is normally built in with the charging circuitry which these products don’t have. Instead, they leave this to battery remanufacturing companies who add this protection to the battery itself. It’s a very simple circuit design normally consisting of a small circular PCB (printed circuit board) around 17mm in diameter (just thinner than the battery itself) attached normally to the bottom/negative of the battery. A small nickel strip or thin wire runs to the top of the battery and is attached to a button top which is then fixed to the flat top positive terminal.. Over this, they place an extra battery wrap, normally with their branding (Much like with our Keeppower products) This constantly monitors the voltage while in use and when the voltage drops to a pre-programmed level, its disconnects power to the device, safeguarding the battery. If can then be re-charged in the same way as any other rechargeable battery.

Why so many different options?

There are currently several hundred different 18650 batteries available on the market. Different products and devices call for different characteristics and each and every one of them was originally specified for a set purpose and gradually picked up by others when their characteristics fit, much like vaping. A wireless doorbell for example has an incredibly very low drain while idle, waking up only to service a single function (an even then only drawing under 1 amp of current) then goes back to “sleep”. In this instance, a battery that lasts a long time between charging is much better than one that has a very high drain and low capacity. This is why we only offer the highest drain batteries in our Wireless Doorbell battery kits. A cordless drill or E-bike battery on the other-hand requires a large amount of current in order to provide enough power to produce the torque required to drill into brick and steel, or power you and your bike up a hill.

Why can’t you get all of that in one battery?

Capacity and current output are a trade-off. You can have lots of one, lots of the other, a reasonable mix of both but you can’t have your cake and eat it and this is why there are so many options. The limit is in chemistry technology. There’s only so much of each material you can fit in a battery and adding more of something that is good for capacity, takes away room for another which is better for current discharge ability. Until we find or invent new “ingredients” we can use instead of the current ones, this is where the limit lies. As above, different devices/products have different needs and the choice of battery for the job is decided by how much current it needs, and how long it needs to last it for before charging. At the time of writing, 30amps is about the very best that can be achieved from a single 18650 battery. The LG HB2 and LG HB6 in our shop can provide this level of current but with only 1500mAh capacity. Likewise, the LG MJ1 has a capacity of 3500mAh, the highest commonly available capacity on the market right now but because of this, is limited to only 10A constant discharge.

There are lots of batteries being advertised on eBay, Amazon, Alibaba etc with wild figures like “50A constant discharge” and “9000mAh capacity”. These are all LIES. Do not fall for them. It is impossible to have more than 3600mAh in capacity or 30A in constant discharge. At the time of writing, these are the limits of current chemistry technology available to the market. That’s not to say new chemistries aren’t being developed (Lithium Titanate is being developed by Toshiba in their SCiB range, Lithium Sulphur/Li-S by other, privately owned and independent technology companies like Oxis Energy), just that they are currently unavailable to us or at least not in 18650 form.

As you can see, there are a huge number of variables in the products on the market and hopefully this has given you a better understanding as to why some of these differences exist, how to spot them and an insight into selecting the right battery for the job.

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