3 x 21700 Battery Holder - 3-Cell SMT / SMD Surface Mount Socket Case

Specifications

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

• Number of Slots: 3

• Mounting Style: Surface Mount Technology (SMT / SMD)

• Tab Count: 6 (Independent positive/negative tabs for each cell)

• Contact Material: Nickel-plated steel

• Housing Material: High-temp resistant plastic (optimized for reflow soldering temperatures)

Key Applications and Projects

• Low-Profile Power Banks: Building a massive portable charger where keeping the PCB flat against the bottom of the enclosure is necessary.

• Custom Sensor Nodes: Providing extreme, multi-year battery life for remote, solar-assisted LoRaWAN stations.

• Portable Audio Amplifiers: Delivering clean, high-current 11.1V power to custom Bluetooth speaker builds.

Unlock New Capabilities (Project Evolution)

• Battery Protection: Because this is a bare holder, pair it with a 3S Battery Management System (BMS) circuit directly on your PCB. Route the SMT tabs into the BMS traces to ensure your 21700 cells are balanced perfectly and protected from over-charging and deep-discharging.

Package Includes:

• 1 x 3-Slot 21700 Battery Holder (SMT/SMD 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. 18650 cells are narrower (18mm) and shorter (65mm), so they will be too loose to 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 inside the plastic? No. They are not wired together at all. Each of the 3 slots has its own independent tabs. You dictate the wiring configuration (series or parallel) via your PCB traces.

5. What does SMT / SMD mean? SMT stands for Surface Mount Technology (and SMD is Surface Mount Device). It means the metal tabs are completely flat and designed to be soldered flush to the surface of a circuit board, rather than pushed through holes.

6. Why choose SMT over a through-hole (DIP) holder? SMT holders keep the bottom side of your PCB completely flat, which is great for mounting the board flush against a case. They are also much easier for automated robotic assembly machines to install.

7. Can I use this on a standard breadboard? No, the flat SMT tabs cannot be plugged into a breadboard.

8. How many batteries does it hold? It holds exactly three 21700 cells.

9. 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) circuit for safety.

10. Are the spring contacts strong? Yes, the leaf-spring contacts feature raised dimples to concentrate pressure, holding the heavy 21700 cells very securely.

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

12. Will "protected" 21700 cells fit? "Protected" 21700 cells have a small protection 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.

13. 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.

14. 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., pulling 30A continuously), spot-welding batteries is recommended over using spring holders.

15. Does it come with wire leads attached? No, this specific model features rigid, flat metal SMT tabs designed for PCB soldering, not flexible wire leads.

16. How do I solder this to my board? You typically apply solder paste to large rectangular pads on your PCB, place the holder so the tabs align with the pads, and use a reflow oven or a high-wattage soldering iron to flow the solder over the tabs.

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

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, high-temperature plastic designed to withstand the heat of an SMT reflow oven without melting or warping.

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 on your PCB, you should always use three identical, brand new cells of the same brand, capacity, and voltage level.