Button Top battery - The 18650 with raised positive terminal

A button-top battery is a cylindrical battery – usually in the 18650 format, though sometimes also 21700 or 20700 – in which the positive terminal protrudes from the cell body as a small, outwardly curved button. Depending on the manufacturer, this raised positive terminal measures around 1 to 1.5 mm in height and ensures that the cell makes a secure connection even in devices with springless or flat contact plates.

The counterpart is the flat top: here, the positive terminal is flush with the cell casing. Flat-top cells are preferred in industry for permanently welded battery packs, such as in laptop batteries or e-bike batteries. For single-cell applications with screw or spring contacts, however, the 18650 button top is the more common choice.

Important: Button-top cells do not constitute a separate chemical system. Cell chemistry (usually INR or IMR), capacity in mAh and maximum discharge current in amperes are independent of the design of the positive terminal.

Whether you need a button-top or flat-top cell depends on the device. Typical applications in the vaping and lifestyle sectors:

E-cigarettes and battery mods

Most modern battery mods for 18650 cells work with both designs because they have spring-loaded contacts. However, some older or cheaper mods, as well as many mechanical mods without spring contacts, absolutely require a battery with a raised positive terminal, as a flat top would otherwise fail to close the circuit.

Torches and power banks

High-quality torches often have long, narrow contact springs and accept both variants. Compact or specialised models explicitly require a button top – checking the manual saves a lot of hassle here.

External chargers

Common charging cradles such as the Nitecore i2 or Xtar VC4 use movable slides and charge both types without any problems. This is also one of the reasons why the button top has established itself as the ‘safe standard’ in the consumer market.

The positive terminal is just one criterion. When buying a button-top battery, the following points are crucial:

• Match the design to the device: Check your mod’s manual to see whether it requires a button-top or flat-top battery. If in doubt, button-top is more compatible.
• Choose genuine brand-name cells: Samsung, Sony/Murata, Molicel and LG are the four major manufacturers of reputable 18650 cells. Fancy labels with specifications such as “9900 mAh” are fakes – genuine 18650 cells range from 2500–3500 mAh.
• Note the discharge current (CDR): For sub-ohm vapes below 0.2 ohms, you need cells with at least 20 A CDR, such as Molicel P26A or Samsung 25R. Capacity decreases at high currents.
• Check the positive terminal construction: Some button tops are simply metal caps attached to the cell. High-quality cells have an integrated, fixed contact design that cannot come loose.
• Ensure the wrap and insulating ring are intact: Damaged plastic casings pose a safety risk. Check the insulating ring and casing before each use – if there are any cracks, re-wrap immediately or dispose of the cell.

Additionally: always use cells in pairs from the same batch if your mod requires two batteries. Transport them exclusively in a battery box and never loose in your pocket with keys or coins.

Can I use a flat-top cell instead of a button-top cell?

Only if your device has spring-loaded contacts. With rigid or flat contact plates, a flat-top cell will not close the circuit securely – the device will not work or will display an error.

How can I tell if it’s a button top at a glance?

Look at the positive terminal from the side. If it protrudes visibly beyond the cell casing, you have a button top. If it is flush with the rest of the cell top, it is a flat top.

How long does an 18650 button top last?

With normal use of around one charge cycle per day, approximately 300 to 500 cycles, i.e. one to two years. After that, the capacity and internal resistance drop noticeably, and you should replace the cell.

Can I take button-top batteries on a plane?

Only in hand luggage and in a sealed protective case. Loose batteries are prohibited in checked luggage. Specific regulations are set by the respective airline.

A button-top battery is the most compatible design for most devices using single cells – from mechanical mods to high-performance torches. What matters is not marketing promises, but genuine brand quality, the right discharge current and clean wraps. If you want to upgrade your kit, you’ll find suitable cells, chargers and protective cases in our section for batteries, chargers and accessories, as well as the matching battery holders. Take your time to compare and choose the combination that suits your setup.