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There are many various lights currently on the market that are marketed as "designed for E-bikes". They have external power connectors. Of course, the voltage must also match but I am not even there.

My E-bike seems even having some support for lights, as there is the "lights" button on the control panel (seems not doing anything). The engine is Bafang 36V/250W Maxdrive if matters but probably generic advice where to look for may be even more valuable.

I have looked visually around the motor, the control panel, there is no any obvious socket available. Where should I look for the terminals to connect the externally powered light?

I use the bicycle daily for commuting and need lights quite often in the evening. Monitoring over the charging level of the front, rear light, also the main battery requires attention. It would be simpler to watch over the single battery only.

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    I have no idea but maybe there are several models of your battery/controller which share the same control panel. So the lights button doesn’t necessarily indicate the existence of a port somewhere. In Austria and Germany lights had to be dynamo-powered until recently, so it didn’t make sense to add an output to the battery/controller.
    – Michael
    Commented Jul 15, 2021 at 10:25
  • Details of the control system, especially the panel, are far more important than the type of motor. I have worked on e-bike lighting, for a model which powered a front light via the control panel but had an independent rear light. I had to open the control panel and splice wires. You may well have to do the same (with associated warranty risks)
    – Chris H
    Commented Jul 15, 2021 at 10:34
  • My bike has a USB port for providing power, mounted on the handlebars. Presumably the presence and position of such a port will vary from bike to bike.
    – Chenmunka
    Commented Jul 15, 2021 at 10:39
  • BTW some of the cheap lights are pretty poor. The rear light I fitted ("24-36V") turned out to be several white LEDs connected in series with an inadequate resistor even for 24V and a red filter, also inadequate so combined with the overcurrent the light looked pink.
    – Chris H
    Commented Jul 15, 2021 at 10:39
  • @Chenmunka is that switched and intended for lighting? There are 5V-input lights, especially front ones, but the ones intended for e-bikes normally run at the main battery voltage
    – Chris H
    Commented Jul 15, 2021 at 10:40

2 Answers 2

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It may depends from brand to brand, the only way to find it being to look at the technical documentation.It is however very likely that it will be on the motor unit itself (but may not be at an obvious place), as the power has to arrive there at the first place. The screen/control units can then just send the signal to turn on/off the lights.

For Shimano, that publishes some information, the connectors are on the motor itself. The following picture is a screenshot from the DU-EP800 user manual, for illustration.

For Bosch, the dealer's manuals are not available online, but it looks from internet research that it's on the motor unit as well. The discussion in this thread indicates that plugging the light is not sufficient, and it needs to be enabled by a a certified dealer.

Note that according to compatibility chart published by Lezyne, stock Bafang motors only provides 6V/0.5A (vs 13.5V/2.2A max seen on other units), which is not sufficient for the Lezyne lamps listed in this chart (but it can be done if the motor is fitted with an additional component).

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My understanding is that the EU has a bunch of rules about bike lights that don't apply anywhere else in the world.

So in Europe your bike is much more likely to have a hard-wired light and perhaps a dynamo to power it. With the advent of ebikes, a hard-wired battery powered light becomes more convenient.

Your Bafang motor is not an ebike - the controller is probably a generic part as is the dashboard panel. That it has a Lights button doesn't mean there's anything to connect it to and control.

Instead, check the details of your specific brand of bike, and if theres nothing useful, look for generic details on your controller and console boards. It is possible there's a +12V DC switched terminal, or it might be a 6V AC terminal intended to use existing dynamo lights. Or some third option is also conceivable... a 3V circuit with the frame as ground might also be a valid option because its 2x carbon battery cells, like the bike lights of old.

If you're not up for manipulating wires, then perhaps stick with some battery lights for your bike. At least they won't run down your main motive battery.


European law varies from state to state.

Example:

Germany – Dynamos are required by law, they must be attached, the battery light alone is not permitted (except for race bikes)...

Austria – Battery lights are allowed and they can be detachable...

Switzerland - Battery lights are allowed and they can be detachable, must be seen from 100m, ...

Netherlands – Battery lights are allowed, detachable or fixed to the body, ...

France – Battery lights are allowed, detached only, ...

page 16 of https://www.anec.eu/images/Publications/technical-studies/ANEC-RT-2012-TRAF-002.pdf

Upshot, in Germany your ebike is not legal for lighting unless it has a dynamo as well. Nominally, your ebike with a hardwired light is still battery powered. Whether this is enforced, is another question.

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    Th EU rules weren't fully harmonised by the time the UK left. 6VAC would make sense but I've never seen that as an output and given the range of voltage and frequency you can get from a dynamo, all modern lights rectify to DC while incandescents don't care, thus 6VDC would be reasonable. But as far as I can tell, even Germany doesn't require permanently fixed lights, it's just that dynamo lights are very common and are permanently fixed
    – Chris H
    Commented Jul 15, 2021 at 12:15
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    Because e-bike are fairly harmonised, they do have to be pedelecs everywhere in the EU, and that means they have to function as a normal bike if the battery is flat, and you need lights after dark. Relying on the motor's battery for lighting may not be wise, but a backup set could be very small
    – Chris H
    Commented Jul 15, 2021 at 12:17
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    I think that requirement for dynamo likely have been dropped as most the bicycles I see around use battery powered lights. It made more sense in the past when the battery was much more likely not to be good when needed.
    – nightrider
    Commented Jul 15, 2021 at 19:53
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    @h22: In Germany, battery-powered clip-on lights are road-legal since 2017, but only if they are certified by the Kraftfahrt-Bundesamt. You aren't even required to carry them with you during the day – but note that if you happen to be surprised by a rain shower, a fog bank, smoke, or something else that impairs visibility and you don't carry your light, then it's time to walk. The standard rules still apply though: you must have one white front light and a red rear light, the front light must be brighter than 10 lux, the rear light must be mounted higher than 25cm off the ground, etc. Commented Jul 18, 2021 at 9:38
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    §67 StVZO is the most relevant, I guess. Commented Jul 18, 2021 at 19:39

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