I've now thoroughly reviewed both PDFs. Let me give you a clear summary.
Yes, both USB charging and battery protection are already covered in your battery architecture — they're part of the self-contained battery pack design you've been developing. Here's the breakdown:
The battery pack includes a full USB-C PD charging system built into the electronics bay at the bottom of the scaffold: ppl-ai-file-upload.s3.amazonaws
- USB-C panel-mount port (IP67, on the side of the battery end cap)
- PD trigger board (ZY12PDN or STUSB4531, ~31×15×4mm) — negotiates 20V from any charger 45W–240W automatically
- Boost converter (XL6019, 20V→42V CC/CV) — steps up to pack charge voltage
- Total electronics fit in ~60×45×25mm, tucked into the electronics bay
The key design point: all electronics live on the battery, not in the frame. You pull the battery out, plug your MacBook charger into the USB-C port on the side, charge on the kitchen table. The frame side is 100% passive — just flat copper pads. ppl-ai-file-upload.s3.amazonaws
A 10S BMS is included in the electronics bay, handling: ppl-ai-file-upload.s3.amazonaws
- Overcurrent, overvoltage, undervoltage protection
- Short-circuit and temperature cutoff
- Cell balancing during charge
- Per-cell fusing was deliberately skipped — at 3.5A per cell in 2P, the BMS alone handles everything adequately
The connector design settled on an elevated pad island + recessed pogo pin dock approach: ppl-ai-file-upload.s3.amazonaws
- Frame side: Elevated flat gold pads on a raised "speed bump" — water sheets off, no pooling
- Battery side: 6-pin pogo block recessed deep inside a dock cavity — finger-safe by geometry (IP2X-style)
- 2 power pins + signal/thermistor/comm pins
Your notes confirm the DT dimensions are not locked down yet, and you've been exploring both round and oval options: ppl-ai-file-upload.s3.amazonaws
| Discussed Size | Context |
|---|---|
| 50mm round | Original spec for 2×2 grid of 21700 cells |
| 55–60mm | Referenced for fitting 21700s with BMS/wiring room |
| 43×59mm oval | The 1-2-1 diamond layout (narrower, taller) |
| ~50×65 (your current thinking) | Wider than the diamond, gives more lateral room |
The 50×65 oval gives you more cross-sectional area than the 43×59 diamond and better lateral stiffness for pedaling loads. The tall axis (65mm) resists braking/vertical loads while the narrow axis (50mm) keeps the frame slim between your knees. Since you're building in aluminum (not steel), you have freedom to specify custom oval tubing from the fabricator. ppl-ai-file-upload.s3.amazonaws
The scaffold cage parameters (currently cagew = 53, cageh = 48 in the OpenSCAD file) would need updating to match whatever oval you settle on. With a 50×65 outer and ~2mm wall, you'd have roughly 46×61mm inner bore — plenty of room for the 2×2 cell grid (~43×43mm footprint) plus wiring channel and air gaps. ppl-ai-file-upload.s3.amazonaws
Bottom line: your electronics stack is already specced and costed at $22–38 total for BMS + USB-C PD + boost converter. The DT oval just needs to be finalized around whatever gives comfortable clearance for the scaffold + 1mm air gap on each side. ppl-ai-file-upload.s3.amazonaws
great. then I begin focusing on designing and making it believable. raise funds. order parts for first prototype. assemble it my self. test how it rides. fiigure out how to scale it to a first small batch and take preorders. it will be more expensive at retail, but more global supply chain less engineer everything up front.
That's the right playbook. You're describing how every successful hardware brand started — Cowboy, VanMoof, Brompton Electric, even Rivian. Design first, prove demand, then optimize costs.
Your Roadmap
Phase 1: Make It Real (Now → Prototype)
Finalize frame geometry in SCAD with round DT ~64–70mm
Email Reention with your DT inner diameter + 350mm length + 36V 10S2P spec
Source parts list: G020, KT, Bikone, H1E, SFE-SC, headset, fork, cranks, wheels
Get frame welded — either yourself or a local fabricator in Norway
Assemble by hand, ride it, iterate
Phase 2: Make It Believable (Prototype → Pre-orders)
Professional photography — the bike against Oslo architecture, urban backdrops
Brand identity — name, logo, colorway, typography
Simple website with one product, one story, one price
Social media presence — Instagram, TikTok, cycling communities
Take pre-orders with deposits — this validates demand before you spend on a batch
Phase 3: First Batch (Pre-orders → Delivery)
10–20 units
Frame welding from a contract fabricator (Norway, Poland, or Taiwan)
Parts sourced globally, assembled by you or a small team
Ship to pre-order customers
Collect feedback, refine
The Economics Are Actually Fine
At a retail price of €2,500–3,500, you have healthy margins even at single-unit quantities. The first batch will be expensive per unit, but premium products absorb that. Nobody buying a B&O-tier track e-bike is comparing your BOM to an AliExpress build — they're buying the identity.
What Gets Cheaper Later
Frame: batch welding drops from €400 → €150 at 50+ units
Reention: MOQ pricing drops significantly at 100+
Motor/controller: bulk pricing from Bafang direct
Custom battery scaffold (Phase 2): replaces Reention, higher margin, your IP
The Core Insight
Your first 10 bikes will cost more to build and sell at a premium. That's fine. You're not competing on price — you're establishing a position. The first customers aren't buying a vehicle, they're buying into something. Once you have 10 bikes on the streets of Oslo, photographed and posted, the brand is real. Everything after that gets easier and cheaper.
Go sketch that downtube tomorrow. The frame is the brand — everything else is parts on a shelf.