Could one of these gizmos add brake lights to my ebike?

[fireaza]

Hey guys! I'm trying to add brake lights to my ebike, since it only came with a saddle LED, which obviously doesn't light up when I apply the brakes. I was thinking I could simply add a proper brake light and wire it to my controller, but it seems like for some bizarre reason, the more expensive controllers that use waterproof connectors don't have a brake light connector, unlike the cheap controllers with the SM connectors which always seem to have that.

Anyway, I looked around on Aliexpress, and I found two gizmos that appear to add this functionality:

https://www.aliexpress.com/item/1005002361646120.html

https://www.aliexpress.com/item/1005007531487836.html

It seems like these work by tapping power from the headlight and using the brake cutoff signal to control the brake light. They seem similar but different, one uses waterproof connectors, and the other one doesn't. Does anyone know which might be suitable for my purposes? Or if there's some other way to add brake lights to my bike? To provide more information about my ebike, it uses a 1000W hub motor. I'm unsure what controller it uses, as it's attached deep inside the frame and I can't see the label. Let me know if there's other information that you might need!

 

[fill]

The brake cut off is generally a simple Normally Open connection which is 'made' to engage the cut off either by a reed switch (2 wire config) or a hall sensor (3 wire config), so piggybacking a brake light relay to the system is easy enough especially when there are existing Y cables for adding 'gear sensors' or further systems are also available.

However the easiest solution is imho a $10 'smart-ish' rear light fitted with a motion sensor which will just require bolting on..

 

[fireaza]

Do you have any recommendations? This is largely for legal reasons, so it should be a proper "pull the brake lever and the brake light lights up" type of setup, so a motion sensor probably won't cut it.

 

[aae34]

In case you can't touch the controller, perhaps a totally separate diy circuit would do?
All it would need is the battery voltage. Stepdown that, add a relay and switches for
brake light after it(<20usd parts from aliexpress). The actual brakelight does dictate
what you need in between it and the battery voltage, but all it takes is 4parts and
some wiring + waterproofing it.

If the bike has hydraulic brakes, pressure sensors would be much cleaner option
than adding any switches to the existing brake levers.

 

[fireaza]

In case you can't touch the controller, perhaps a totally separate diy circuit would do?
All it would need is the battery voltage. Stepdown that, add a relay and switches for
brake light after that(<20usd parts from aliexpress). The actual brakelight does dictate
what you need in between it and the battery voltage, but all it takes is 4parts and
some wiring + waterproofing it.

That sounds very similar to one of the gizmos I linked to, it looks to me like one of the connectors is the same one the battery uses. Would it do what you're describing, but in a ready-to-go package?

If the bike has hydraulic brakes, pressure sensors would be much cleaner option
than adding any switches to the existing brake levers.

It does have hydraulic brakes! A clean install sounds nice, can you tell more about this option?

 

[slaphappygamer]

My bike only came with a static rear light. I used something like this kit. I added front turn signals as well.

 

[aae34]

It does have hydraulic brakes! A clean install sounds nice, can you tell more about this option?

Magura makes these two-wire brake pressure switches, which is all you need for controlling a relay(or a brakelight which takes 2pin input):

 

[99t4]

The hydraulic pressure switch is an elegant solution. But bleeding brakes is not for the faint of heart. Know what you're getting into.

 

[glennb]

There’s also “deceleration lights”, with rechargeable battery. No wiring required.

 

[fireaza]

My bike only came with a static rear light. I used something like this kit. I added front turn signals as well.

How do you wire that up? It looks like you use the Y splitters to add the brake signal to the mix, but how do you power it? Does your controller need a wired tail light?

 

[fireaza]

The hydraulic pressure switch is an elegant solution. But bleeding brakes is not for the faint of heart. Know what you're getting into.

Ah, I do know how to bleed brake lines, but having to cut the brake lines to install this sensor, re-bleed it, and still needing some way to power the brake light since my controller doesn't appear to have a wire for a tail light, sounds like a bit of a pain!

 

[fill]

Its generally a bad idea to use controller lighting connections when provided as the switching transistor is generally limited to the current it can handle and aftermarket lamps often burn out this circuit with further knock on and side effects to the controller often 'fatal'.

To wire up take the lamp power voltage from the battery and step it down through an appropriate voltage limiter if necessary, 48v would probably fry a 12v lamp.. A y splitter cable in the brake cut off will give you access to the brake cut off signal (4-5v) logic high (test this) when brakes are applied.

this logic voltage should enable you to switch a relay or ssr used to brake the continuity of your brake lamp power circuit, so when brakes are applied the signal voltage switches on the relay/ssr to power the brake lamp.

 

[slaphappygamer]

How do you wire that up? It looks like you use the Y splitters to add the brake signal to the mix, but how do you power it? Does your controller need a wired tail light?

You won’t need to use your existing tail light since the kit comes with one. You’ll replace the one you currently have with the one in the kit. Add the existing brake sensors to the harness. The Y split connection allows connection to the controller as well. With that particular kit, use the white plug with the yellow and black to feed it power. That kit accepts 24-48v.

I haven’t used that exact kit, but I have this similar one. There are other kits that also include front turn signals, if you were looking to do that as well.

I agree, using the controllers headlight feature isn’t the best option to feed anything else, other than only one headlight. I used the positive and negative that feeds the display, though others may not like that set up. I just tapped to the power. I’ve used a kit wired like this for almost 3 years now. Check my signature for more detail.

 

[fireaza]

How would I go about installing a similar kit when my controller uses waterproof connectors and not SM connectors? I've seen a few kits that have waterproof connectors, but I'm not sure how to know which one I would need. My controller has one of those cables that splits off into multiple connectors which connects things like the light, throttle and light, and I'm not sure how you know what you can connect.

 

[slaphappygamer]

oh. That was a headache. The waterplugs. I installed one on my wife’s RadRunnerPlus and the kit had the small higo connector, as opposed to Julet. The julet plug is larger than the higo. I had to get an extension cable for the light blue plug that feeds the brake light and cut it. Cut the plug on the kit (similar to this) to make what I needed. Then I tested many ways to get the wires where they go. Be sure to identify the exact name of the plug your controller has and the plug on the kit. You should have a better experience than I did.

 

[fireaza]

The plugs on my bike say "Julet" so I'd say that's what they are! I've bought M8 sized Julet connectors in the past, and they plug into the existing connectors. Should any kit with "Julet" branded waterproof cables work..? A lot of them mention "center motor" but mine is a hub motor, are these kits still usable? They also mention they're for Bafang motors, but it's my understanding that most brands of ebike motors are simply clones of Bafang motors, so you'd assume they would be compatible..?

 

[slaphappygamer]

I can’t say if there is a standard pinout and that all julet plugs match, but the kit I bought plugged in between the controller and 9pin harness. I think the kit (for the RadRunnerPlus) came with an 8 pin plug and I had to take matters into my own hands.

If all Julet plugs are a standard pinout configuration, then should be good. I’m not sure what the difference, in wiring, would be between a center motor and a hub motor.

 

[99t4]

Should any kit with "Julet" branded waterproof cables work..?

Yes in theory but there can be some that look similar but are just enough off that they don't fit.

Many of us like to buy the ones called extension cables, that gives you both ends (M/F) and some length to work with before you start cutting and splicing.

 

[fireaza]

Hmmm, I've found this kit for Julet connectors:

https://www.aliexpress.com/item/1005006563120218.html

But there's actually multiple options for a "Julet" connector: JULET 811 (8 pins), JULET 813 (8 pins), JULET 913 (9 pins) and JULET 911 (9 pins). How am I supposed to know which is correct? Also, which cable would this be connected to? The main cable that splits off into the throttle, light, etc, or would it replace the headlight like in slaphappygamer's kit? Sorry! This is all very new to me!