Dummies guide to powering 12V Lights from main battery?

xylene23nyc

100 mW
Joined
Jan 16, 2022
Messages
48
Are there any general guides or good resources for learning how to safely tap into main Ebike batteries for a 12v DC-DC converter that will power commonly found 12v lights + handlebar controls? Most of the YouTube videos I find for this are not in English. Ebike school only has a guide for powering lights/accessories from an external battery.

My goal is to power 12v LED front/rear lights from the main Ebike battery : front/rear/and handle bar controls/turn signals + flasher relay

I am also a bit confused about what is a safe/recommended way to minimize risk of damaging battery/bms/controller/my home?
Inline fuses, breakers, where to add them, where to buy them and what models should be used? Terminal blocks a good idea for the lights wiring?

I have one Battery 48V with 30Amp continuous BMS (small anderson connector) and also will soon upgrade to a 72V battery 100 amp continuous BMS (Xt60). Also have a 12V DC-DC converter up to 15Amp that works with 48-120V. I'm guessing I should start by getting an Anderson to xt60 adapter and then a xt60 Y cable with one output going to the DC-DC converter and other output to controller? Not sure where I should add any inline fuses or breakers or which ones to use. I have tools for crimping and soldering cables.

Thanks in advance
 
Wow alot of feedback here. I was hoping to copy your set up... but nothing past ur original post. Bummer, did u end up figuring it out? If u found any good info or instruction/guidance...id be very grateful if u wanted to share!
 
Wow alot of feedback here. I was hoping to copy your set up... but nothing past ur original post. Bummer, did u end up figuring it out? If u found any good info or instruction/guidance...id be very grateful if u wanted to share!
Many controllers have a Lights lead already waiting to just plug into a lamps ,controlled via your headset lcd screen i/o. If the wires are not in place you may on inspection of your controller pcb find an unpopulated solder pad labeled lights+ Might be +6v tho not +12v just add the wire and select a suitable ground (-ve).

If no controller light option, then as long as your not fitting silly hi power blinding beams a simple tap from the battery power leads/terminals to a suitable step down converter should be straight forward. just double and triple check polarity before making any connections.
 
Wow alot of feedback here. I was hoping to copy your set up... but nothing past ur original post. Bummer, did u end up figuring it out? If u found any good info or instruction/guidance...id be very grateful if u wanted to share!


There are lots of posts about DC-DC setups for lighting/etc, some in individual threads, some within various build threads (like my SB Cruiser or CrazyBike2, or Teklektik's Yuba)

If you are going to use it for lighting, get one with 13.6v output, not 12v, if you are going for any form of DOT lighting.
 
Many controllers have a Lights lead already waiting to just plug into a lamps ,controlled via your headset lcd screen i/o. If the wires are not in place you may on inspection of your controller pcb find an unpopulated solder pad labeled lights+ Might be +6v tho not +12v just add the wire and select a suitable ground (-ve).

Keep in mind most of those can only output a tiny amount of power on those lighting ports--the tiny transistor used to switch them on and off can't handle much power. If you're using lights that came on a bike with the bike's original controller, this works fine, but adding aftermarket lights, etc., you have to be sure not to use something more powerful than the original or risk destroying the lighting control (at best) or the internal votlage converter in the display or controller next best case, whcih can take out the entire display/controller system worst case.
 
The easy way is like this:


I use an adjustable converter for my headlight, which needs about 26V give or take. But I have one of the above which I'll employ to operate a klaxon horn on my bike when I get around to it.

Because the switch mode electronics in that DC-DC converter consume some power even if there's no load, you should try to switch it on the main battery voltage side.
 
Keep in mind most of those can only output a tiny amount of power on those lighting ports--the tiny transistor used to switch them on and off can't handle much power. If you're using lights that came on a bike with the bike's original controller, this works fine, but adding aftermarket lights, etc., you have to be sure not to use something more powerful than the original or risk destroying the lighting control (at best) or the internal votlage converter in the display or controller next best case, whcih can take out the entire display/controller system worst case.
This is what I did. It fried the daughterboard that managed the lights. No more holding "up" to activate my lights. I was lucky when it was just this board and not the controller itself.

I've since then run a dc-dc 48v-12v converter wired from my display voltage. I intercepted the 48v and also added a keyswitch.
 
Sorry for the late follow up guys. I had clue u guys replied bc ididn't have my alerts turned on. I really appreciate the feedback and suggestions. I'll follow up to show u what I come up with or if I have any questions. Everyone on here seems more than willing to help the newbies figure things out. That's what I luv about these forums. I'm new to ebikes but luckily I've got alot of experience building esk8's & working with DC power in vehicles. So I'm hoping I can make something happen! 🤷‍♂️🤣 thx again guys!!
 
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