Utilizing Brake Light Signal from Controller

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e-doggies
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Utilizing Brake Light Signal from Controller

Many of the smaller brush-motor controllers include a connector to power a brake light. For a 48V battery and 48V controller, I must assume that the output to the brake light is also 48V? I want to avoid having a 48V lamp. All other electrical accessories: headlights, taillights, horn, and 80A solenoid to connect the controller to the battery, are all 12V from a 48V to 12V DC/DC Converter.

Here's my question:

How can I power a 12V brake lamp from the 48V brake signal coming from the controller?

(1)Could I use a relay with a coil that could handle 48V? How hard would this be to find, and how much would it cost?

(2)Could I use another DC/DC Converter from 48V to 12V dedicated to just the brake light? I would need at least 25-30W, I think.

(3)Any other ways to do this?

I appreciate any ideas or comments.

Harlow

e-doggies
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Re: Utilizing Brake Light Signal from Controller

Would it be possible to build a voltage-divider circuit with two resistors in series?

colin9876
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Re: Utilizing Brake Light Signal from Controller

or even put 4 small 12v bulbs in series and have a cluster lamp lol!

chizzer
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Re: Utilizing Brake Light Signal from Controller

Hi,

Have you actually dropped a volt meter across the brake light signal cables and checked what the output is? Moight be an idea to check it. I say this because my speed controller is powered from a 24v system, but the brake light output is actually 6v, going to a 6v bulb.So it's not safe to assume that because it's a 48v supply it's a 48v brake light output.

If it is, I would suggest a relay.

Hope that helps,

Chizz

Toronto_ebiker
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Re: Utilizing Brake Light Signal from Controller

Your best bet would be to add another DC/DC converter. Resisters are not a good idea, since you need 2 watt resisters just to connect one single 20ma led and even then the resister gets hot. You can get cheap DC/DC converters on ebay.

chas_stevenson
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Re: Utilizing Brake Light Signal from Controller

I use 1/4 watt resistors on my 36 volt battery to run LEDs and have never felt it the least bit warm. I use a 1 K Ohm resistor which works great.

Grandpa Chas S.

Toronto_ebiker
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Re: Utilizing Brake Light Signal from Controller

I'm running 2 watt 2k7 resistors for some of my lighting on my ebike. I had originally used 1/4 watt, but they were extremely hot to touch and then I changed them to 2 watt resisters (still fairly hot). I used the led calculator to determine the resister I needed. Maybe I'm using the wrong one? My source voltage is 54 volts with a forward diode voltage of 3.2v at 20mA.

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