When looking for the smallest cart battery for your vape pen, you have several options that offer portability and discretion. Here are some of the smallest cart battery available:

1. Rokin Rage: This is one of the smallest oil vape pens on the market, fitting in the palm of your hand. It features a 280mAh rechargeable lithium-ion battery and Rokin's Powerwave™ Technology for a smooth vaping experience. It has a single voltage setting of 3.6V and includes a USB-C charging cable and lanyard .

2. CCell Palm 510: This battery is known for its compact size and ease of use. It has a fixed voltage of 3.7V and a 500mAh battery, providing over 250 puffs per charge. The cartridge fits inside the outer shell for protection, and it uses a buttonless design for convenience .

3. Magic 710: This is a mini vape with a fixed voltage of 3.5V and a 380mAh battery. It features a magnetic cartridge connection and is known for its sleek, stylish design that is easy to use and conceal .

4. Slim 510: This vape pen is super slim and offers variable voltage settings, letting you customize your vaping experience. It has a preheating function and a 280mAh battery life, making it a good choice for on-the-go vaping .

5. v-mod 2: Designed for thick oils, this compact vape pen has a 900mAh battery and variable voltage design with pre-heat function. It's compatible with all 520 thread cartridges and offers a discreet and easy-to-use option .

These smallest cart battery are designed to be portable and discreet, making them ideal for those who want a small vape that can be taken anywhere. When choosing smallest cart battery, consider factors such as battery capacity, voltage settings, charging method, and compatibility with your cartridges.