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When choosing a battery, there are some very important aspects to consider, otherwise the device you put the battery in will either not work or it could burn out, so it's a good idea to check what you need to look for when choosing the right battery before you buy to make sure you don't miss out!

One of the most important aspects is size, so choose the size of battery that the manufacturer recommends for your device, because if you buy a smaller or bigger one, it won't fit, it won't reach the terminals or it will rattle, so if it says 18650 size, for example, then buy one that's not smaller or bigger. What else should you look for to choose the right battery???

Grouping by size

The most common Li-ion cell size is 18650, but also 14500 and 26650 are common, 10440, 16340, 18350, 18500, 32650, and recently 20700 and especially 21700 are becoming more common. In practice, these numbers represent the size of the battery, for example, if we look at the 18650, the first two characters indicate the diameter of the cell, in our case 18 mm, and the second two characters indicate the length of the cell, which is 65 mm. To make life a bit more complicated, some batteries can vary in size by a few mm, so even though it's 18650, it can still be 18.5 mm wide and up to 70 mm long, especially if it's protected (more on what that means later), so it's worth making sure you know what battery will fit in which device you want to use before ordering.

Grouping by voltage

  • Nickel-based batteries, which have a nominal voltage of 1.2 V, which in practice means that they operate between 0.8 and 1.4 V.
  • Lithium-based batteries, but with an operating voltage of 1.5 V, these were created to replace the previous group, operating between 1 and 1.8 V
  • Lithium-ion at 3.0 V (typically CR2 and CR123 sizes)
  • LifePO4 batteries with 3.2 V
  • Li-ion 3.6 V (between 2.8 and 4.2 V)

These are not interchangeable, so don't put a 3.6 V battery in a device expecting a 1.2 V device, or you'll end up with a nasty mess. A 1.5 V battery will simply ruin a standard 1.2 V charger. But you can put a 3.0V battery in a charger that is wired for 3.2V, but there is no reason for a bigger difference.

Grouping by material

Currently there are two main battery types on the market, nickel based (1.2 V) and lithium based. (3,7V)

Li-ion

Lithium-ion batteries are currently the most common (we mainly sell them), for a number of reasons:

Lithium batteries are much lighter and more durable than nickel-based batteries
No memory effect
They are lighter and less expensive than conventional batteries
Even a depleted cell can deliver at least 2.8V compared to NiCd or NiMH batteries of 1-1.25V, although it is not advisable to go below 3V as this will compromise battery life, and not all chargers can bring them to life
However: unprotected ones are more sensitive, they can be overcharged, which can destroy the battery, and a sealed battery can be dangerous, so only buy a quality battery and charger from a reliable source

Protection
Li-ion batteries can be divided into two broad categories: protected and non-protected. Protected batteries have a small circuit at the bottom or top that serves safety purposes, disconnecting the battery cell from its terminals in case of overcharging, over-discharge or short-circuiting. Accordingly, unprotected batteries require more care but are cheaper than their protected counterparts. The protection is marked on the batteries with a PCB.
Importantly, protected batteries are longer, for example, 18650 protected batteries can be up to 70 mm instead of 65 mm.

Discharge Current
There are high drain and low drain battery types, a number that indicates how much current can be drawn from a battery at a given moment. This is important because for many devices it is irrelevant, e.g. electric cigarettes prefer high drain batteries, but for many other devices the Discharge Current is also important.

Max and continuous discharge current
For batteries, we distinguish between the above two figures, because while the first one can be maintained by the battery until the end of its capacity, the second one can only be maintained for 1-2 seconds, so it is worth paying attention to what is written on the battery and what is advertised.

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