Ordering a replacement e-bike display online feels straightforward until it arrives and the plug doesn't fit.
Here's what most riders don't realize: the #1 reason displays come back as "dead on arrival" isn't a factory defect — it's a connector mismatch. A display that looks identical to the listing can still refuse to power up, or worse, damage your controller, if the pins or protocol don't match.
The good news? You don't need to be an electrician to figure this out. Most e-bikes, e-scooters, and e-MTBs use one of two connector types. Identify yours in 30 seconds and you'll never order the wrong part again.
The Two Connectors You'll Actually Encounter
Walk into any e-bike parts forum or scroll AliExpress reviews, and you'll see connector names thrown around: Julet, SM, 5-pin, 6-pin, waterproof, JST... It sounds like a lot. In practice, two connectors cover the vast majority of aftermarket displays on the road.
1. Round 5-Pin Julet (Waterproof) — The E-Bike Standard
If you have a pedelec, a hub-motor conversion kit, or an e-MTB, this is almost certainly what you're looking at.
What it looks like: A round, cylindrical plug, usually green or black, with a screw-on locking ring that twists tight to keep water out. Five metal pins sit inside.
Where you'll find it:
- KT-series controllers (KT-LCD3, KT-LCD5, KT-LCD8)
- Bafang BBS01 / BBS02 mid-drive motors (UART versions)
- Most generic hub-motor conversion kits from Chinese OEMs
- The vast majority of 250W–1000W city e-bikes and fat-tire e-bikes
Protocol: UART2 (also called UART No.2 or "second protocol"). This is the most widely used display communication standard in the e-bike industry — and the reason why so many third-party displays from different manufacturers are cross-compatible.
2. SM 6-Pin (QS-S4 Style) — The E-Scooter Standard
If you have a performance e-scooter (Zero, Apollo, Kaabo, VSETT), this is your connector.
What it looks like: A small, rectangular plastic plug — think JST-style, about the size of your thumbnail. No screw ring, no waterproof housing on its own (the scooter's housing and silicone boot do that work). Six pins inside.
Where you'll find it:
- Zero 8/9/10/10X scooters
- Apollo Explore / Ghost / City (2019–2021)
- Kaabo Mantis series
- YUNLI and JINGBO controllers (used across dozens of scooter brands)
- The ubiquitous QS-S4 throttle-display combo
Protocol: UART No.2 (also written UART2 or "second protocol"). This is a specific flavor of UART used by nearly all Chinese scooter controllers.
What About the Pentagonal CAN Bus Plug?
You might see a pentagonal, "house-shaped" plug on premium systems from Bosch, Shimano STEPS, Brose, or the newer Bafang mid-drives (M600, M620 CAN versions). That's CAN bus, and it's a different world.
If your bike uses one of these systems, stop here. Third-party displays are generally not compatible — the protocol is locked to the manufacturer's ecosystem. You'll need an OEM original replacement. This guide is for the rest of us.
How to Identify Your Connector in 30 Seconds
You don't need to open the controller case or measure anything. Just follow these three steps:
Step 1 — Power Off and Find the Controller End
Turn off the bike and remove the battery for safety. Follow the cable from your display down the handlebar and frame until it plugs into the controller. That's the connector you need to match — not the display end.
Step 2 — Count the Pins
Look inside the socket. Count the metal contact points:
- 5 pins → either a round Julet 5-pin or an SM 5-pin
- 6 pins → either a round 6-pin or an SM 6-pin
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7 pins → usually an SM 7-pin (dual-motor or extended features)
Step 3 — Look at the Shape
Now glance at the housing:
- Round with a screw-on ring → Julet waterproof connector
- Small rectangle, no screw ring → SM (JST-style) connector
Match It to Your HAYTRIX Order
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What you see on your bike
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What to order from HAYTRIX
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Round, 5 pins
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5PIN
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Round, 6 pins
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6PIN
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Small rectangle, 5 pins
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SM5PIN
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Small rectangle, 6 pins
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SM6PIN
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Small rectangle, 7 pins
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SM7PIN
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Still unsure? Snap a clear photo of the connector (both the socket and the plug) and send it to us before ordering. We'll confirm the match.
HAYTRIX Covers All Five Connector Types
You shouldn't have to choose between a display that works and a display that fits. Every HAYTRIX LH-series display is available with your choice of connector:
- 5PIN — round Julet waterproof (e-bike standard)
- 6PIN — round Julet waterproof
- SM5PIN — rectangular JST (generic e-bike / scooter controllers)
- SM6PIN — rectangular JST (QS-S4 / Zero / Apollo / Kaabo style)
- SM7PIN — rectangular JST (dual-motor / extended systems)
All models run UART No.2 protocol, support 24V–60V auto voltage detection, and carry an IP65 waterproof rating. When you place your order, just tell us which connector your controller uses — or attach a photo — and we'll ship the matching version. We also supply custom cable lengths and OEM packaging for bulk orders.
Frequently Asked Questions
Can I use an adapter to convert a 5-pin plug to 6-pin?
No. Adapter cables rewire the pins arbitrarily and can damage both the display and the controller. Order the connector version that matches your bike.
My connector looks identical to the listing, but the display won't turn on. What now?
The housing matches, but the pinout or protocol may not. Send us a photo of both ends of your cable — we'll confirm whether the pinout lines up before you continue troubleshooting.
Is "UART2" the same as "UART No.2"?
Yes. You'll see it written as UART2, UART No.2, second protocol, or protocol 2 — they all refer to the same standard used by most Chinese e-bike and scooter controllers.
Can I order a sample first before buying in bulk?
Yes. We ship sample units worldwide so you can test fit and function before committing to a bulk order. Contact us to request one.
Wrong-connector returns are avoidable. HAYTRIX manufactures UART2 LCD displays for e-bikes, e-MTBs, and e-scooters from our factory in China, with five connector options, 24V–60V auto-voltage, and IP65-IP67 sealing. Tell us what your ride has — we'll make sure it fits the first time.
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