Enquiries answered within 5 hours
Get a Quote
Products
Hailong Series Silver Fish Series Integrated & In-Frame Downtube Rear Rack Water Bottle
OEM & ODM
Factory
Contact
Get a Free Quote

Downtube Battery Cases

Bolt-on housings that mount above or below the down-tube, taking 18650 packs to 104 cells. The largest family we hold tooling for.

15 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 openings from 355 to 465 mm. ABS, high-temperature grade.

MOQ 1 · quote in 5 hView ALX030 downtube case

Showing the 15 models with a full spec page. The complete range of 15 is shown below. Every one is an empty shell — you supply cells, BMS and harness. Measured openings and cell ceilings for every model: see the full dimensions table.

How many Downtube empty battery cases are there?

15 — every one with its own spec page and a measured drawing. Every downtube housing we mould is listed below. All are empty housings: no cells, no BMS.

ModelCellsCommon configurationsOpening / sizeFitmentMaterialVoltage
ALX03018650 — 40 / 52 / 65 cells · 21700 — 40 cells18650: 13S5P · 16S4P · 10S6P · 20S3P · 21700: 10S4P · 20S2P · 13S3P · 16S2POpening 355 / 415 / 465 mm (18650) · 435 mm (21700)DowntubeABS—
ALX030B18650 — 40 / 52 / 65 cells · 21700 — 40 cells18650: 13S5P · 16S4P · 10S6P · 20S3P · 21700: 10S4P · 20S2P · 13S3P · 16S2POpening 355 / 465 / 531 mm (18650) · 435 mm (21700)—ABS36 V – 72 V
ALX030D18650 — 40 / 52 / 65 cells · 21700 — 40 cells18650: 13S5P · 16S4P · 10S6P · 20S3P · 21700: 10S4P · 20S2P · 13S3P · 16S2POpening 355 / 415 / 465 mm (18650) · 435 mm (21700)Downtube——
ALX05818650 — 30 / 40 / 52 / 65 cells · 21700 — 20 / 28 cells18650: 13S5P · 16S4P · 10S6P · 20S3P · 21700: 14S2P · 13S2P · 10S2POpening 365 / 414 / 531 mm (18650) · 414 mm (21700)Downtube——
ALX077B18650 — 40 / 52 / 65 / 78 cells · 21700 — 40 / 52 cells18650: 13S6P · 10S7P · 14S5P · 16S4P · 21700: 13S4P · 10S5P · 16S3P · 14S3POpening 392 / 462 / 508 mm (18650) · 392 / 462 mm (21700)Downtube——
ALX08618650 — 30 / 40 / 52 / 65 cells18650: 13S5P · 16S4P · 10S6P · 20S3POpening 370 / 500 mmDowntube——
ALX08918650 — 52 cells18650: 13S4P · 10S5P · 16S3P · 14S3POpening 420 mmDowntube——
ALX09918650 — 40 / 52 / 65 / 78 cells · 21700 — 50 / 52 cells18650: 13S6P · 10S7P · 14S5P · 16S4P · 21700: 13S4P · 10S5P · 16S3P · 14S3POpening 355 / 425 / 465 (18650) · 425 / 450 (21700) mmDowntube——
ALX099B18650 — 40 / 52 / 65 / 78 cells · 21700 — 50 / 52 cells18650: 13S6P · 10S7P · 14S5P · 16S4P · 21700: 13S4P · 10S5P · 16S3P · 14S3POpening 355 / 425 / 475 (18650) · 425 / 455 (21700) mm—ABS36 V – 72 V
ALX10018650 — 52 / 68 / 78 cells · 21700 — 68 / 80 cells18650: 13S6P · 10S7P · 14S5P · 16S4P · 21700: 10S8P · 16S5P · 20S4P · 13S6POpening 355 / 415 / 465 (18650) · 355 / 425 / 450 (21700) mmDowntube——
ALX100A18650 — 52 / 65 / 78 cells · 21700 — 40 / 50 / 52 cells18650: 13S6P · 10S7P · 14S5P · 16S4P · 21700: 13S4P · 10S5P · 16S3P · 14S3POpening 355 / 415 / 475 (18650) · 355 / 425 / 455 (21700) mm—ABS36 V – 72 V
ALX119A18650 — 40 / 52 / 65 cells · 21700 — up to ~46 cells18650: 13S5P · 16S4P · 10S6P · 20S3P · 21700 (~): 14S3P · 10S4P · 20S2P · 13S3POpening 340 / 391 mmDowntube——
ALX12718650 — 40 / 52 / 91 / 104 cells · 21700 — 52 / 65 cells18650: 13S8P · 10S10P · 20S5P · 14S7P · 21700: 13S5P · 16S4P · 10S6P · 20S3POpening 382 / 462 / 498 mmDowntube——
ALX14318650 — 52 cells18650: 13S4P · 10S5P · 16S3P · 14S3POpening 278 mmDowntube——
ALX148B18650 — high-capacity build—Opening 473 mmDowntube——
About this series

Why do assemblers choose a Downtube case?

15 Downtube models across 36 V – 72 V systems, on 18650 and 21700 cells — empty shells, MOQ one piece. Bolt-on housings that mount above or below the down-tube, taking 18650 packs to 104 cells. The largest family we hold tooling for.

Downtube housings bolt on above or below the down-tube — visible on the frame, and removable, so you reach the pack without opening anything. That is the difference from an in-frame housing, which disappears inside the tube and is mostly used on folding bikes, where it folds with the frame. Downtube is also 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 531 mm on ALX030B, covering 18650 packs from 30 to 104 cells and 21700 packs from 20 to 65.

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.

Also known as: buyers also know this family as Polly or Dolphin cases — Polly for the square-shouldered bodies, Dolphin for the slim long profile. The names describe the shape, not a single factory — our Polly, Dolphin and Shark size guide maps the dimensions to the names.

  • Twelve body sizes, 278–531 mm — Match the opening to the frame, not the frame to the case.
  • 18650 to 104 cells, 21700 to 65 — 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 Compare all six formats
Downtube e-bike battery case, ALX030, shown from the drive side
Downtube housingBolts on above or below the down-tube · 18650 to 104 cells
Other fitments

Which mounting format fits your frame instead?

Six mountings, six jobs: Hailong and Silver Fish dock on the down-tube, integrated moulds into the frame, downtube suits standard tubes, rear rack carries cargo, and water bottle fits small packs. Choose by frame first, then by cell count.

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
Start here

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.

Get Your Quote

Common questions about Downtube

How many cells fit in a Downtube battery case?
Across our 15 Downtube housings the largest mould takes 104 cells on 18650 and 80 on 21700 — the same mould physically holds fewer of the fatter 21700 format. Cell count per model is listed on each product page.
What voltages do Downtube cases cover?
Across the 15 models the range spans 36 V to 72 V. Voltage follows the cell count you build to — 10S is 36 V, 13S is 48 V, 14S is 52 V — so pick the case by cells, not by the label voltage.
Can I order a single Downtube case?
Yes — MOQ is one piece on every model in this series, quoted within five hours. Single-piece orders ship from stock for the common moulds; rare configurations are moulded to order.
Are downtube cases waterproof?
The cases are moulded as dust- and splash-resistant shells; the pack itself is not waterproofed by the case. For wet-climate builds we recommend the flame-retardant grade with sealed cable exits.
WhatsApp Get a Quote