Fogstar Energy 3800 18650 Battery

Fogstar FS3800 18650

The Fogstar Energy 3800 is an 18650 lithium-ion cell built for regulated vape mods that take removable batteries. The 18650 format measures 18mm in diameter by 65mm in height - the most widely used battery size in vaping. The FS3800 prioritises capacity over discharge rate: 3800mAh is on the higher end of what an 18650 cell can hold, and the 10A continuous discharge rating makes it best suited to dual-battery regulated mods at low to medium wattage rather than high-drain single-battery sub ohm setups.

It is an unprotected flat-top cell, so it is designed for use in regulated mods with built-in safety protections. Each battery comes in a protective carry case.

Key Features

• 3800mAh capacity
• 10A maximum continuous discharge
• 3.6V nominal voltage, 4.2V maximum charge voltage
• Flat-top design
• Unprotected cell
• 18650 format - 18mm diameter, 65mm height
• 200-500 cycle life before noticeable capacity drop
• Sold with a protective carry case

Capacity

3800mAh is towards the upper end of 18650 capacity. Standard 18650 cells used in vaping typically land between 2500mAh and 3500mAh, so the FS3800 offers longer runtime between charges than most. This makes it a good choice for vapers who use dual-battery mods at moderate wattage and want to stretch out their sessions. If you need the maximum capacity an 18650 can offer and your setup runs within this cell's discharge limits, the FS3800 delivers that.

Discharge Rate

The 10A maximum continuous discharge rate is the key spec to check before buying. This is a capacity-optimised cell, not a high-drain cell - it trades discharge headroom for higher mAh. In a dual-battery regulated mod at moderate wattage, the draw is shared across both cells, which brings each cell well within the 10A limit. In a single-battery mod running at high wattage, or in any sub ohm setup where the per-cell amp draw is high, this battery is not the right choice. If you are unsure whether your setup is compatible, use Ohm's law to calculate the current draw and compare it against the 10A rating.

Voltage

The FS3800 operates at 3.6V nominal and charges to a maximum of 4.2V. These are standard lithium-ion figures shared by the vast majority of 18650 cells. Your regulated mod handles output voltage conversion, so the nominal voltage is less critical day-to-day than the capacity and discharge rate. Always use a dedicated lithium-ion charger that cuts off at 4.2V - overcharging degrades the cell faster and is a safety hazard.

Flat-Top Design

The FS3800 uses a flat-top positive terminal, which is what almost all modern regulated vape mods require. Button-top cells are typically only needed for older devices or certain torches. If you are unsure which your mod takes, check the battery bay contacts - a flat positive end means flat-top. Most 18650 dual-battery box mods take flat-top cells.

Unprotected Cell

This is an unprotected battery with no internal protection circuit, which is standard and correct for regulated vape mod use. Regulated mods have their own electronic protections built in, including short-circuit protection, over-discharge cutoff, and temperature monitoring. Do not use unprotected cells in devices with no electronic protection. Check your battery wraps regularly - a torn or damaged wrap on an 18650 is a short-circuit risk and the cell should be re-wrapped or retired immediately. Fogstar sell replacement wraps and insulators separately.

Safe Storage and Handling

Each FS3800 comes in a hard plastic carry case. Never carry loose 18650 cells in a pocket or bag alongside keys, coins, or other metal objects - direct contact can short the cell. Charge on a dedicated lithium-ion charger and do not leave batteries unattended while charging. Fogstar recommend recycling cells after 200-500 charge cycles once you notice noticeable capacity drop-off. 18650 batteries can be recycled at most UK supermarkets and electronics retailers with a battery recycling point.

What's in the Box

• 1 x Fogstar Energy 3800 18650 Battery
• 1 x Protective carry case