DIY 18650 Dual USB Power Bank Module with LCD Display

Prototyping and Engineering Tips from Robogears

• Polarity is Absolute: This module does not have reverse polarity protection on the battery terminals. Connecting the "B+" and "B-" wires backward, even for a millisecond, will instantly destroy the main control chip. Always double-check your connections with a multimeter before soldering.

• Parallel Connection Only: You can connect multiple 18650 cells to increase capacity (e.g., 10,000mAh), but they must be connected in parallel (all positives together, all negatives together). Never connect batteries in series (7.4V or higher), as the module is strictly designed for a 3.7V input.

• Thick Wiring Matters: When drawing 2.1A, thin jumper wires will cause a voltage drop, making the module think the battery is empty. Use short, thick 20 AWG to 22 AWG copper wires for the battery-to-module connections for maximum efficiency.

• Initial Activation: After soldering the batteries for the first time, the screen might not turn on immediately. You usually need to plug in a Micro USB charger for a few seconds to "activate" the protection circuit and wake the module.

Package Includes

• 1 x Mobile Power Boost DIY 18650 Lithium Battery Digital Dual USB Module

Disclaimer

Handling lithium-ion batteries requires extreme caution. Ensure all batteries used in a parallel pack are of the same brand, capacity, and voltage level to prevent internal overheating or fire.