4 x 21700 Battery Holder - 4-Cell PCB Mount DIP Storage Case

Specifications

• Supported Battery Size: 21700 (21mm diameter x 70mm length)

• Number of Slots: 4

• Mounting Style: PCB Through-Hole (DIP pins)

• Pin Count: 8 (Independent positive/negative for each cell)

• Contact Material: Nickel-plated steel springs

• Housing Material: High-temp resistant plastic (typically ABS/PC)

• Pre-drilled Mounting Holes: Yes (in the base of the slots)

Key Applications and Projects

• DIY Power Banks: Building a massive 20,000mAh+ portable charger by wiring four 21700 cells in parallel.

• Robotics & RC Vehicles: Delivering high-voltage, high-current power by wiring the cells in series for heavy-duty motor controllers.

• Off-Grid IoT Nodes: Providing months of backup power to a solar-powered sensor array using a custom PCB.

Unlock New Capabilities (Project Evolution)

• Battery Protection: Because this is a bare holder, pair it with a 4S Battery Management System (BMS) board. Route the pins from this holder into the BMS to ensure your 21700 cells are balanced perfectly and protected from over-charging and deep-discharging!

Package Includes:

• 1 x 4-Slot 21700 Battery Holder (PCB Mount)

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What size battery does this hold? It is specifically molded to hold 21700 lithium-ion batteries, which are roughly 21mm in diameter and 70mm in length.

2. Will an 18650 battery fit in this holder? No. Because 18650 cells are narrower (18mm) and shorter (65mm), they will be too loose and will not make a reliable electrical connection.

3. Will a 20700 battery fit? Generally, yes. A 20700 is only 1mm narrower than a 21700 and the same length, so the spring contacts can usually accommodate it.

4. Are the batteries wired in series or parallel? Out of the box, they are not wired together at all. Each slot has its own independent pins. You dictate the wiring configuration (series or parallel) via your PCB traces.

5. What are the sharp metal spikes on the bottom? Those are through-hole solder pins. They are designed to be pushed through holes in a printed circuit board and soldered into place.

6. Can I use this without a custom PCB? Yes, you can carefully solder standard wires directly to the pins on the bottom, though mounting it to a perfboard or custom PCB provides the best mechanical stability.

7. How many batteries does it hold? It holds exactly four 21700 cells.

8. Does this holder have built-in overcharge protection? No. This is simply a mechanical plastic holder with metal contacts. You must connect it to an external Battery Management System (BMS) for safety.

9. Are the spring contacts strong? Yes, the leaf-spring contacts are designed to hold the heavy 21700 cells very securely, even in vibration-prone environments like RC cars.

10. Does it come with a cover or lid? No, this is an open-top chassis design.

11. Will protected 21700 cells fit? "Protected" 21700 cells have a small circuit board added to the top, making them slightly longer than 70mm (often 73mm-75mm). They will likely be extremely tight or may not fit at all. This holder is best for unprotected, flat-top cells.

12. Can I use flat-top and button-top batteries? Standard flat-top cells fit perfectly. Button tops may fit but will compress the springs heavily.

13. What is the maximum current these contacts can handle? Standard spring contacts are typically rated for 3A to 5A continuous draw per slot. For extreme high-drain applications (e.g., 30A vape cells), spot-welding batteries is recommended over using spring holders.

14. What are the holes inside the battery slots for? Those are pre-molded mounting holes. You can put small screws through them to permanently mount the plastic holder to your project's chassis.

15. Does it come with wire leads attached? No, this specific model is the PCB-mount version and features rigid metal pins, not flexible wire leads.

16. How do I know which side is positive and negative? Usually, there are small + and - symbols molded into the plastic inside each slot. Generally, the flat contact pad is positive, and the curved spring contact is negative.

17. Can I cut this in half to make a 2-slot holder? While technically possible if you have the right cutting tools, it will compromise the structural integrity of the plastic. It is better to buy a dedicated 2-slot holder.

18. Is this waterproof? No, it is an open electrical component. It must be kept dry or placed inside a sealed waterproof enclosure.

19. What material is the casing made of? It is made of rigid, heat-resistant plastic, usually a PC/ABS blend, designed to withstand the mild warmth generated by charging/discharging batteries.

20. Can I mix old and new batteries in this holder? It is highly discouraged. If you are wiring the batteries together in series or parallel, you should always use four identical, brand new cells of the same brand, capacity, and voltage level.