Li-ion Battery Case Adapter — Rechargeable Battery Holder with USB Output

Turn Rechargeable Cells Into a Power Bank.

This Li-ion battery case adapter lets you use standard rechargeable lithium cells as a portable USB power source. Load it with compatible cells, connect your device to the USB output, and you have a power bank that you can refuel with fresh cells rather than replacing the entire unit. It’s a practical, cost-effective approach to portable power for anyone who already uses rechargeable cells in other devices.

Features

• Li-ion cell compatible — holds standard rechargeable lithium cells (check variant for cell size compatibility: 18650, 21700, etc.)
• USB output — charges phones, earbuds, and other USB devices from the installed cells
• Built-in protection circuit — over-discharge protection prevents cells from being drained below safe voltage levels
• Replaceable cells — swap in fresh cells when depleted rather than discarding the entire unit
• Compact housing — lightweight case keeps cells organized and protected
• LED indicator — shows power output status

Who It’s For

• Flashlight and electronics hobbyists who stock rechargeable cells and want a dual-purpose power bank
• DIY enthusiasts who want a customizable, refillable portable charger
• Preppers and off-grid users who want a power bank that can be refueled with spare cells
• Anyone who wants a sustainable alternative to disposable or non-replaceable power banks

How to Use

1. Insert fully charged Li-ion cells into the case, observing correct polarity (+ and − markings).
2. Close the case and connect your device to the USB output port.
3. The LED indicator will confirm power output is active.
4. When cells are depleted, remove and recharge using a dedicated cell charger, then reinstall.

Frequently Asked Questions

Are cells included?
No — cells are not included. Purchase quality cells from reputable brands (Samsung, LG, Panasonic, Sony) for best performance and safety.

What cell size does it accept?
Check the variant details for compatible cell sizes (18650, 21700, or other formats). Using the wrong cell size will prevent proper fit and function.

Can I charge the cells while they’re in the case?
This depends on the specific model — some cases include a USB input for in-case charging, others require removing cells for charging in a dedicated charger. Check the variant details for charging method.