Connecting a 9-pin cable to an ebike controller with an 8-pin connector

Question

I don't want anyone to drown in details, but long story short, I had to change my ebike's controller and I wanted to buy something more powerful. I bought a controller that supports 48V but sadly, I missed a detail. My current controller is exactly like the one I bought, except the cable that connects to the throttle, the brake sensors and the display has 9 pins whereas the one that I bought has 8.

This part is very important: I cut them to see what is going on and I saw an extra brown wire. The rest of the wires are exactly the same color

What is the brown cable for? Can I bypass it?

Answer 1

You need to find the pinout of both sides, and ideally wire a small adapter between the two standards.

Colour by itself is not enough information, you need to know which wires are voltage, ground, data, and connect them appropriately.

Black is commonalty used as ground, but that's not guaranteed, and every other colour is less standardised.

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Your other problem is to know that the protocol between each unit is compatible. If the head unit is made by the same company as the motor, you're more likely to succeed, but even then there are changes across the years.

Answer Buy the right head unit with the right cabling. Then sell your existing head unit second-hand on an auction website - someone might need it if theirs was broken/stolen.

Answer 2

The 8-pin or 9-pin male connector on a generic (i.e. mostly brands that are from China and Tawain like Bafang, Kunteng and Lishui) ebike controller is meant to connect a 1to4 cable (for the 8-pin) or a 1to5 cable (for the 9-pin). A 1toX cable (where X is a number) is a cable with a big connector on one end that connects to the controller and X connectors on the other end that connect to cockpit accessories.

The 1to4 cable is meant to connect a throttle, the left brake sensor, the right brake sensor and the HMI (human-machine interface which is usually an LCD or a more basic LED display).

The 1to5 cable is meant to connect the same things as the 1to4 but adds an extra connector for a headlight (probably the extra brown wire you are referring to). The light needs its own dedicated power wire since you can usually turn it on or off with the HMI.

If your new controller has an 8-pin connector, you simply need to buy an 8-pin 1to4 cable. Controllers with an 8-pin connector will usually have a separate wire for the headlight but some does not have any. Those cables are fairly cheap, so you are probably better off buying the right cable than trying to modify your old one.

A word of caution

The pinout of those cables is not standardized. While they seems to loosely follow one, there are known exceptions. The green 5-pin connector for the HMI can be different between Bafang and Lishui/KT. Here is a picture from the EggRider v2 display compatibility page:

Also, some brake sensors use the yellow 3-pin connector, while some use the red 2-pin connector.

Finally, there are two main types or waterproof controller side connectors for the 1toX cable (I am not talking about the number of pins here). It can be one from the HiGo Main Signal series (or compatible from other connector brands), such as the 8-pin Z812 which is mostly found on Bafang controllers:

or a connector that is similar to the 2-3-4-5-6-pin HiGo Mini B series, such as this 8-pin which is mostly found on KT/Lishui controllers: