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Downtube Battery Cases

Housings that sit inside the down-tube, taking 18650 packs to 104 cells. The largest family we hold tooling for.

12 models 36 V – 72 V 18650 / 21700 MOQ 1 piece
ALX030 65-Cell Downtube — empty e-bike battery case
ALX030 · DOWNTUBE

65-Cell Downtube

The long-body downtube in the range — 18650 packs to 65 cells or 21700 to 40, on a 465 mm opening. ABS, high-temperature grade.

MOQ 1 · quote in 5 hDetails
ALX030D Downtube, Single or Dual Tube — empty e-bike battery case
ALX030D · DOWNTUBE

Downtube, Single or Dual Tube

Same 65-cell envelope as ALX030, supplied in either a single-wall or double-wall tube so the frame line can stay thin where it matters.

MOQ 1 · quote in 5 hDetails
ALX058 Long Downtube, 21700 Ready — empty e-bike battery case
ALX058 · DOWNTUBE

Long Downtube, 21700 Ready

The longest opening in the downtube family at 515 mm, sized around 21700 cells and still taking a 65-cell 18650 pack.

MOQ 1 · quote in 5 hDetails
ALX077B High-Capacity Downtube — empty e-bike battery case
ALX077B · DOWNTUBE

High-Capacity Downtube

Built for the biggest packs that still fit inside a frame — 78 x 18650 or 52 x 21700, on a 538 mm opening.

MOQ 1 · quote in 5 hDetails
ALX086 Slim Tube Downtube — empty e-bike battery case
ALX086 · DOWNTUBE

Slim Tube Downtube

A narrow section for frames with little aesthetic room. Takes 52 or 65 x 18650 on a 375 or 500 mm aluminium tube.

MOQ 1 · quote in 5 hDetails
ALX089 Downtube, 52-Cell — empty e-bike battery case
ALX089 · DOWNTUBE

Downtube, 52-Cell

The straightforward 18650 downtube: 52 cells, 420 mm opening, ABS. The low-cost starting point for a commuter frame.

MOQ 1 · quote in 5 hDetails
ALX099 Mountain Downtube, 21700 — empty e-bike battery case
ALX099 · DOWNTUBE

Mountain Downtube, 21700

Wider section for MTB and small-wheel frames, taking 52 x 21700 or 65 x 18650 on a 445-450 mm opening.

MOQ 1 · quote in 5 hDetails
ALX100 Downtube with Power Bank Port — empty e-bike battery case
ALX100 · DOWNTUBE

Downtube with Power Bank Port

A downtube housing that carries a USB output, so the pack can charge a phone as well as drive the bike. 18650 to 78 cells or 21700 to 80.

MOQ 1 · quote in 5 hDetails
ALX119A Downtube Battery Compartment — empty e-bike battery case
ALX119A · DOWNTUBE

Downtube Battery Compartment

Sealed compartment layout for 18650 packs to 65 cells, with the cover and latch as a separate assembly.

MOQ 1 · quote in 5 hDetails
ALX127 Long Downtube, 104-Cell — empty e-bike battery case
ALX127 · DOWNTUBE

Long Downtube, 104-Cell

The volume leader: 104 x 18650 or 52 x 21700 in a 498 mm opening, for cargo and long-range builds.

MOQ 1 · quote in 5 hDetails
ALX143 Compact Downtube — empty e-bike battery case
ALX143 · DOWNTUBE

Compact Downtube

Short 278 mm body for small frames and step-throughs, taking 52 x 18650.

MOQ 1 · quote in 5 hDetails
ALX148B Large-Capacity Tube Downtube — empty e-bike battery case
ALX148B · DOWNTUBE

Large-Capacity Tube Downtube

Round-section tube housing for high-capacity 18650 builds, with the end caps moulded separately.

MOQ 1 · quote in 5 hDetails

Showing all 12 models in this series. Every one is an empty shell — you supply cells, BMS and harness.

About this series

Why buyers choose Downtube

Downtube housings are inserted into the tube itself rather than hung off a dock, so nothing shows on the outside of the frame. That makes them the default choice on city, commuter and step-through bikes — and the hardest family to re-tool, which is why we keep twelve body sizes on the shelf.

The range is organised by opening length, because that is the number that decides whether a pack fits a given frame. Openings run from 278 mm on the compact ALX143 up to 538 mm on ALX077B, covering 18650 packs from 40 to 104 cells and 21700 packs from 28 to 52.

Every model is quoted as an empty shell with the end caps, cover and latch as separate mouldings, so you can specify the assembly route your line already uses.

  • Twelve body sizes, 278–538 mm — Match the opening to the frame, not the frame to the case.
  • 18650 to 104 cells, 21700 to 52 — The widest capacity span of any family we mould.
  • Separate caps, cover and latch — Assemble to your process, or take them loose.
  • MOQ 1 piece — Test a single housing against your frame before committing.
Get a Quote All battery cases
Downtube e-bike battery case, ALX030, shown from the drive side
Downtube housingSits inside the tube · 18650 to 104 cells
Other fitments

Compare with the rest of the range

Hailong Battery Cases

The universal fitment. Waterproof ABS and PC+ABS shells with key lock, cable exit and mounting kit options, sized for 18650 or 21700 packs.

Silver Fish Battery Cases

Tapered shells that slide into a frame or seat-post carrier — the retrofit standard for folding bikes, mountain frames and conversion builds.

Integrated & In-Frame Battery Cases

Hidden housings that sit inside the down-tube, plus conversion kits with aluminium-alloy reinforcement.

Rear Rack Battery Cases

Flat rack-mounted housings for cargo, delivery and long-tail builds — to 104 cells, without widening the bike.

Water Bottle Battery Cases

Mounts on standard bottle bosses — the lowest-cost way to add range to a frame with no down-tube space.
Ten Haitian injection moulding machines running in a line at the ALX factory in Guangzhou
Moulded in house10 Haitian injection moulding machines
Finished e-bike battery cases racked ready for dispatch
Racked and readyEmpty shells, inspected before dispatch
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Tell us your voltage, cell type and dimensions

That is all we need to point you at the right case. Quoted within five hours, MOQ one piece.

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