4-cell 21700 lithium battery pack with wires, supports series/parallel connection

Product Name: 4-cell 21700 Lithium Battery Holder (with Wires, Supports Series/Parallel Connection)

Appearance and Structural Features:
Overall Structure: This is a black four-slot battery holder designed specifically for accommodating four 21700 cylindrical lithium batteries (diameter 21mm, length 70mm). The batteries are arranged in four parallel rows, giving the holder an almost square shape (93mm x 85mm), which greatly optimizes the use of space and makes it suitable for installation in flat, wide device bases.

Materials and Manufacturing:
Shell: The main body is made of black engineering plastic (usually PP or ABS) with a matte finish, providing good insulation and impact resistance.
Contacts: Each slot has a high-elasticity nickel-plated spiral spring at one end (negative pole) and a metal spring/connector at the other end (positive pole), ensuring secure battery contact and reliable conductivity.
Bottom Reinforcement: As shown in the back view, the bottom is reinforced with ribs and multiple screw mounting holes, enhancing the overall structural strength.

Functional Design (Key Features):
Wired Output: Red and black wires are led out from the side (red for positive, black for negative), with the ends pre-stripped for easy direct soldering or crimping of terminals, eliminating the need for secondary processing on the battery holder.
Mounting Holes: Multiple round screw holes are provided on the sides and bottom of the holder, allowing for secure fixation to the device's base plate or bracket to prevent displacement during use.
Polarity Indication: The slots clearly mark the positive and negative poles (⊕ / ⊖) and the "L21700X4" designation to prevent incorrect battery installation.
Open Design: It's an open-type structure and typically needs to be used in conjunction with a device enclosure, which provides protection and battery retention.

Dimension Specifications (Based on Image Markings):
Total Length: Approximately 93mm
Width: Approximately 85mm
Height: Approximately 21.8mm (excluding spring protrusions)

Electrical Characteristics:
Voltage and Capacity: Four 21700 lithium batteries typically have a nominal voltage of 3.6V / 3.7V (about 4.2V when fully charged).
Connection Method: The internal circuit of this type of battery holder is usually designed for series connection (outputing approximately 14.8V / 16.8V) or parallel connection (outputing approximately 3.7V with four times the capacity). Following the common "L21700X4" model convention, unless specified otherwise, it's mostly used for series boosting, but parallel versions also exist. Users should confirm the actual output voltage with a multimeter before use.