Hi all,

Sorry if this is in the wrong section or I’ve approached this from the wrong way.

I have a question regarding electronics and my ebike.

Basically I have a 52v battery (58.5v charged).
I have a connected controller that has a 5v output with low mA capacity. This is my desired method as then the controller will be able to turn the lights on and off without the need of additional switches on handlebars.
I want to run 12v LED off this set up.
I planned to use a step down dc-dc converter that will take battery voltage down to 12v. However I would like to use a relay or contactor that will operate using the 5v wire in order to control these lights.
Is there a really obvious choice to use ?
I basically want the existing controller to be able to turn the lights on and off, it has a 5v output that can’t handle over 500mA, so I want that to be able to turn on the step down transformer via a relay or contactor so I can run easy to find 12v led running at a few watts.

Thanks for any help

 

Hi all,

Sorry if this is in the wrong section or I’ve approached this from the wrong way.

I have a question regarding electronics and my ebike.

Basically I have a 52v battery (58.5v charged).
I have a connected controller that has a 5v output with low mA capacity. This is my desired method as then the controller will be able to turn the lights on and off without the need of additional switches on handlebars.
I want to run 12v LED off this set up.
I planned to use a step down dc-dc converter that will take battery voltage down to 12v. However I would like to use a relay or contactor that will operate using the 5v wire in order to control these lights.
Is there a really obvious choice to use ?
I basically want the existing controller to be able to turn the lights on and off, it has a 5v output that can’t handle over 500mA, so I want that to be able to turn on the step down transformer via a relay or contactor so I can run easy to find 12v led running at a few watts.

Thanks for any help

Trying to understand what you say:

• You have an ebike with 52V battery
• You have some undefined/undescribed type of controller
• The controller has a 5V output with "low mA capacity". I understand "low mA capacity" to mean something in the 1-50mA range, but your later statement indicates that you might mean 500mA. Which is correct?
• "Something," not yet described, is your desired method.
• I don't know what switches on handlebars has to do with your question.
• You wish to drive a "12V LED" (array) using "this" setup. Does "this" refer to the following paragraph "I planned to use..."?
• Summary: You want to use a 5V output from some existing controller to control a 52VDC-to-12VDC converter (do you already have a converter circuit?) to drive one or more (how many?) easy-to-obtain 12V LEDs (automotive?, how much current does each 12V LED draw?). You wish to control the LED on/off state by turning the DC-DC converter on and off (via a relay driven by the 5V signal), with the 12V LED always connected to the converter output.

If I have captured your meaning in my Summary, please answer the few questions raised in the summary. Then we can offer suggestions.

 

Trying to understand what you say:

• You have an ebike with 52V battery
• You have some undefined/undescribed type of controller
• The controller has a 5V output with "low mA capacity". I understand "low mA capacity" to mean something in the 1-50mA range, but your later statement indicates that you might mean 500mA. Which is correct?
• "Something," not yet described, is your desired method.
• I don't know what switches on handlebars has to do with your question.
• You wish to drive a "12V LED" (array) using "this" setup. Does "this" refer to the following paragraph "I planned to use..."?
• Summary: You want to use a 5V output from some existing controller to control a 52VDC-to-12VDC converter (do you already have a converter circuit?) to drive one or more (how many?) easy-to-obtain 12V LEDs (automotive?, how much current does each 12V LED draw?). You wish to control the LED on/off state by turning the DC-DC converter on and off (via a relay driven by the 5V signal), with the 12V LED always connected to the converter output.

If I have captured your meaning in my Summary, please answer the few questions raised in the summary. Then we can offer suggestions.

Hi thanks for the reply.
Apologies for not being very clear.

To clarify a few things;
The motor is connected to a handlebar mounted controller. This displays speed and voltages etc. This is also where the peripherals connect to (throttle, speed sensor, selected power mode, etc.).

I was going to order a small step down dc-dc converter from eBay. Haven’t bought it yet.

Would have one rear red LED light.
And two front LED (a bright light to light up off road in dark, and a less bright one to use on the road).
I don’t imagine that this will be above a combined power consumption of 15w for all three.

And yes the configuration you described is exactly as I hope to have the set up operating.

I wasn’t aware of the defintive of low mA. I meant 500mA and Anything else was a typo.

The method I tried to describe, but it would be a button on existing controller that controls on/off signal at 5v/500mA max)
This would control a relay that would control the on/off of the dc-dc transformer, which would power the led lights.
This was the only way I could think that would allow me to use 12v LEDs that draw current above 500mA.

 

I planned to use a step down dc-dc converter that will take battery voltage down to 12v. However I would like to use a relay or contactor that will operate using the 5v wire in order to control these lights.
Is there a really obvious choice to use ?

If your battery doesn't allow you to access a point around 12V, a buck (step down switching) converter would be the way to go.

To minimize current consumption, you can use transistors, MOSFETs, or solid state relays (SSRs) instead of mechanical relays. Transistors or MOSFETs will be less expensive than SSRs.

I don’t imagine that this will be above a combined power consumption of 15w for all three.

Don't guess. Get the specs for the lights you intend to use before you start making assumptions.

 

The simplest would just to use a relay, controlled by the 5V, to power the DC-DC converter.
It could be a mechanical type, or a solid-state type (SSR) which tend to be more expensive.
If you go with an SSR it must be a DC output type (most are AC output only).