DC/DC converter hook up help.

[Ham549]

I want to put a DC/DC 48v-12v converter on my e-bike. To do this I would wire it in parallel with my controller. However I don't want to have any power go through the DC/DC converter without my controller being on (therefore no accidental leaving the lights on when I park). To do this I was thinking of using some kind of transistor or relay or solid state relay useing the the wires going to my power switch as the trigger voltage. Does anyone have any ideas or schematics for how to set this up. The DC converter is rated at 10A so at least I know that the component I need should be rated for that much or above.

 

[biohazardman]

Why not do it the easy way and hook it up to the output side of your battery switch? It's what I did for my brothers bike and werqs well as when the bike is powered up the DC-DC converter gets powered up and his headlight comes on. Reminds him if he forgets to turn the bike power off as well cuz the light will still be on if this is the case.

 

[Ham549]

I don't have a battery switch and since my controller has a lock out I am assuming that no current will flow through the switch when it is locked out. Therefore if my DC/DC converter relies on power being sent through the switch to work no one can play with my bike and turn the lights on ex unless it is locked up. However I do need a battery switch but I don't know of any good suggestions for one, would a circuit breaker switch work?

 

[marty]

Turn off controller lights go off. DC/DC converter that powers the lights has a negative input trigger. Transistor and resistors in diagram have not been tested. I did not design this. I just drew the picture.

Here is same drawing in PDF format.
View attachment controler_box03.pdf

 

[beppe000]

I see 3 way of doing that:
1- if you can open your controller and have the proper schematics you can hook up the 12v (or maybe 14v) power line which should be inside your controller.
in you dont want or cant do this...
2- if you have a led battery meter which turn on only when your controller is on, then you can use the 48v line on this line to operate a relay or better (because it would consume fewer current) a mosfet switch, or another kind of transistor based switch(like the one with 2n3904 posted by marty).
3- buy a sold state relay (or another type of relay if you prefer) which have a control(input) of 5v and 10-20mA max, and a load(output) >48v 10A: you will connect the input line of the relay to the 5v power line (+ and -) on the throttle or pas (maybe with a protection resistor in series), and the output line will operate your external 48to12v or 48to5v converter connected directly on your battery.

 

[Ham549]

I don't have a battery switch I also am going to use a key switch in series with the controller power switch. That unless the key switch and power is on no power will flow to the DC DC converter.