buck converter (step down converter) question

[joby1]

hey all,

Making a decision soon on buck converter to run possible alarm system, lights, horn etc.

I see two types, one has separated positives and negatives for input and output.

other type has 3 wires, red for high volt input, yellow for low 12v output, and a black common wire.

I am guessing some of these are made for golf carts etc, that may have grounded system..

question is can I use a 3 wire one on an ebike. if so how would it be wired..

something like this, can this type be used for ebike....I have not decided on make/model yet at all, still investigating options. want a decent amount of available watts...

thanks
Joby

 

[fechter]

It should work fine. Just make a splitter for the black wire so one goes to the battery and one goes to the 12 load. You need a pretty hefty switch on the battery side if you want to switch it.

 

[joby1]

thanks for the reply, thats what I was thinking, splitting the negative. just making sure...

what do you mean when you say "switch it", you mean put in a switch before the converter?

I was planning to run some fog lights for headlights, that supposedly can run 12v- 80v, so straight to battery possibly if the wires are heavy enough when I get them, they come with their own switch, I was going to use handlebar switch for led running lights, led tail lights, led brake light and led turn signals, horn and also run a 2-way motorcycle alarm most likely,

my battery has on/off switch and stays in the bike hardwired for charging, I was not really thinking about a switch for the converter that much, if I can shut off the battery with on/off switch, do you think I will still need to switch the converter?? what would be the variables/situations/reasons for having a switch or not having one to turn the converter off? just if I wanted to run bike with only motor? and nothing else? like if I am on a trail or something? I also suppose it would be helpful for maintenance / wiring and such on the 12v components..

thanks for the input it is appreciated greatly, just trying to think ahead...

 

[amberwolf]

The entire time the converter is connected to a power source, even without a load, it will draw power from that source. Might only be a little, but if you leave it all the time and the power source is a battery, and the battery has been discharged low enough, the converter could keep drawing enough power over time before you recharge the battery to bring it so low it damages the battery (unless it has a BMS to prevent that).

 

[fechter]

The battery switch should be OK.
Like amberwolf was pointing out, you need to disconnect it from the battery when not in use as it will be on and cause drain even if there is no load.

 

[joby1]

ok thanks guys,

battery has BMS, and the on/off switch does cut all battery output.

I'll have to ponder on it, as I might get different battery setup in the future...

thanks again
Joby