Positive terminal on the battery: How to recognise the positive side

The positive terminal is the positive end of a battery or rechargeable battery and is marked with the symbol ‘+’. Together with the negative terminal (‘−’), it forms a circuit: electrons flow within the device from the negative to the positive terminal, whilst the technical direction of current is defined in the opposite direction. In cylindrical lithium-ion cells such as the 18650, which is frequently used in e-cigarettes and battery mods, you can identify the positive terminal by the slightly raised cap at one end of the cell.

The negative terminal is located at the flat opposite end and is usually larger in area. The outer casing (wrap) is electrically insulated from the positive terminal but has the same metallic contact as the negative terminal. This is why an undamaged heat-shrink sleeve is crucial: if it tears, the battery can short-circuit. The battery polarity is therefore not just a guide but a safety feature.

In everyday use, there are several reliable methods for identifying the positive side of the battery. On lithium-ion cells, the cap on the positive terminal is usually visibly set apart as a small circle or ring. Additionally, you will find the ‘+’ symbol printed directly on the wrap or the cap.

Markings on the battery mod

In every battery mod, you will see two symbols in the battery compartment: ‘+’ for the side where the positive terminal must be positioned, and ‘−’ for the negative terminal. These markings are usually embossed or printed onto the plastic. Take particular care with dual-battery mods to ensure that both batteries are seated in the correct, often opposite, orientation.

AA, AAA and button cells

With classic disposable and cylindrical cells such as AA or AAA, the positive terminal is also the side with the slightly protruding cap. Button cells (e.g. CR2032) have the ‘+’ symbol on the larger, flat side. This rule also applies to replacement batteries in pod systems with an external battery compartment.

Inserting a battery correctly is quick to explain, but crucial for safety and longevity. You should bear the following points in mind:

• Check the markings: Always compare the ‘+’ on the battery with the ‘+’ in the device. If there are two cells: check each one individually.
• Inspect the wrap: If the heat-shrink tubing is torn, damaged or the positive terminal ring is visibly scratched, replace the battery immediately or dispose of it properly.
• Clean contacts: Wipe the positive and negative terminals with a dry cloth. Dirty contacts increase internal resistance and can lead to a loss of performance.
• Use suitable cells: Only use batteries with sufficient continuous current capacity (e.g. 20 A or more for sub-ohm setups below 0.2 ohms). Refer to the manufacturer’s datasheet.
• Do not mix: Never use batteries of different ages, from different manufacturers or with different charge levels in dual mods. The same applies to mixing with old cells.

A common mistake is inserting the battery against the spring resistance in the compartment. If the battery is difficult to close, it is usually inserted the wrong way round. Force is never the solution – always check the polarity first.

What happens if I insert the battery the wrong way round?

Modern battery mods usually detect incorrect polarity and display an error message such as ‘Check Battery’ or ‘Weak Battery’. However, with unprotected mechanical mods, a short circuit can occur immediately, leading to severe overheating and damage to the cell.

How can I identify the positive terminal without a marking?

On 18650 cells, the positive terminal is the side with the slightly raised, smaller circle. The negative terminal is flat and covers the entire end face. If this is not clearly visible, use a multimeter: place the red probe on the suspected positive terminal – a positive voltage confirms the polarity.

Are the positive and negative terminals arranged in the same way on all batteries?

For cylindrical cells, yes: the positive terminal is always on the cap. For built-in batteries in pod systems, the question doesn’t apply, as you cannot remove them. For LiPo packs with cables, the red cable is always the positive terminal and the black cable the negative terminal.

Can I continue to use a battery with a damaged positive terminal?

No. A deformed cap, signs of rust or a damaged wrap on the positive terminal are clear reasons to discard the battery. Such cells belong in the battery collection point, not in the battery mod.

The positive terminal is a simple but safety-critical detail when handling batteries. By checking the ‘+’ marking, keeping the wrap intact and using only compatible cells, you can avoid the most common mistakes. This care pays off, particularly with high-performance vape setups. You can find suitable cells, safe chargers and mods in our selection of battery mods and accessories, as well as in our charger accessories section – where you can take your time to compare the different models.