Lithium Ion Battery - Connection Types - Explained.

Cylindrical lithium ion batteries are available with a number of connection types. Flat top, Button Top (Unprotected), Protected Button Top and with Tab's. It is important that you select the correct connection type for you application to ensure trouble free operation of your device. Below we outline the differences to ensure you can. Size is also important, popular sizes are 18350, 18650, 21700 and 26650. 

  • Flat Top: The standard connection type, all lithium ion batteries start life this way. These are an unprotected battery typically used in vape devices and other consumer electronics designed to accept a flat top cell. 

Additional connection types are added after manufacture to increase the number of applications they can be used in. Read more about these below.


  • Button Top (unprotected): These batteries have a raised connection on the positive end. We add this with a resistance spot welder to make the batteries compatible with devices such as video doorbells and battery sleds. Not to be confused with Protected Button Top batteries, these do not have an inbuilt protection circuit so must be used in a device that has this feature. 

  • Protected Button Top: Required for Torches, Lasers and other electronics where an onboard battery management system is not present. These batteries are longer than standard 18650's due to an inbuilt low voltage circuit at the bottom and a button top connection at the top. This stops the over charge/discharge of the battery, something that renders a typical unprotected battery unable to be recharged, once the voltage is drained beyond 2.5V. You can find these in their own category Protected Button Top batteries.

  • Tab's: Many consumer electronics have one or several Lithium Ion battery installed inside. When these fail, the device is rendered useless, but it can be possible to replace them. Lithium Ion batteries should not be soldered to directly, this process can increase the temperature of the cell greatly, damaging the chemistry. We can provide the cell with tabs attached via the industry standard, resistance spot welding. This process is almost instantaneous and does not compromise the chemistry. As standard, supplied tabs are 7mm x 0.2mm pure nickel, with a protrusion of 25mm. The tabs are configured in a "C" shape meaning both tabs exit the same side of the cell. If you require a different configuration, or perhaps a complete battery pack, please contact us.

If you need assistance with selecting the correct connection type, please do not hesitate to contact us, we are more than happy to help.