Adding tail lights to E bike

Duneit

New Member
Region
USA
I have a Trek Allant +7 E bike I use for commuting. I tow a trailer with it and want to add tail lights to the trailer. I want to wire from the existing factory tail light to the two new ones I want to add to the trailer. I want to do it this way so that every time my factory headlight and tail light are on, so are the tail lights on my trailer. I do not want to go the rechargeable remote tail light route because of the inconvenience of having to remember to turn them on as its getting dark on my ride or not knowing if they're actually working because the battery might be dead. What I don't know is: will adding this small load to the tail light interfere with the computer? What is the voltage LED light I would need to purchase?
Thanks in advance for any help
 

fooferdoggie

Well-Known Member
you would need to splice in a connection on the original wire then run two wires to the trailer then spit them. but that will will be pretty vulnerable to getting damaged. yjpihj oy costs more a garmin radar will turn on and off from a computer or your phone or their display and let you know when the batteries are low. or this guy again you need a garmin or such to connect them. https://www.rei.com/product/152987/bontrager-flare-rt-rear-bike-light
 

Duneit

New Member
Region
USA
you would need to splice in a connection on the original wire then run two wires to the trailer then spit them. but that will will be pretty vulnerable to getting damaged. yjpihj oy costs more a garmin radar will turn on and off from a computer or your phone or their display and let you know when the batteries are low. or this guy again you need a garmin or such to connect them. https://www.rei.com/product/152987/bontrager-flare-rt-rear-bike-light

Thanks. I looked into that. I don't want my handlebars covered in gadgets and I don't bring or use a cell phone while riding. I am mostly curious about the computer compatibility and output voltage to tail lights.
 

fooferdoggie

Well-Known Member
Thanks. I looked into that. I don't want my handlebars covered in gadgets and I don't bring or use a cell phone while riding. I am mostly curious about the computer compatibility and output voltage to tail lights.
well then your going have to wire then . taillights don't take much juice and I dont think anyone has posted what Bosch will put out in watts. splicing the tail light Wie will be a pain if its tucked in the fender. these should work https://www.amazon.com/Portland-Des...cphy=9032946&hvtargid=pla-1313841892690&psc=1
nut what about two regular lights solder wires to the battery terminals and run the wire to your bike and a battery pack with a switch. I use that method for the lights on our tandem.
 

indianajo

Well-Known Member
I have a garmin varia. https://www.eriksbikeshop.com/garmi...=45fbce74f7e01c88d4e7af940551c2e4#productInfo
It comes with a remote display that tells me the state of both batteries when it first turns on, and turns itself off if the rear taillight goes out. I have the display mounted on a 1/2" plastic stalk on the front battery frame so it is in my line of sight when I am looking forwards. IE a heads up display. The radar is a hysterical crybaby when it comes to warning about trucks 8 lanes away over on the freeway through the fence, or cars crossing right to left the 4 way stop sign I am leaving. But it is a bright rechargeable taillight that tells me if it goes off. I have a backup light powered by AAA batteries, a Brightz pink, if the Varia goes out.
The Varia rear unit is mounted on a 1/2" plastic pipe at the rear of my bike, not on the seatpost as designed. I sometimes carry cargo that would cover over a seatpost light. People have stolen the Brightz once, cut the tie-wraps, and broke another last November when they couldn't get it off the screws . But the Varia, which clips on with rubber o-rings, has so far bamboozled thieves.
 

Duneit

New Member
Region
USA
well then your going have to wire then . taillights don't take much juice and I dont think anyone has posted what Bosch will put out in watts. splicing the tail light Wie will be a pain if its tucked in the fender. these should work https://www.amazon.com/Portland-Des...cphy=9032946&hvtargid=pla-1313841892690&psc=1
nut what about two regular lights solder wires to the battery terminals and run the wire to your bike and a battery pack with a switch. I use that method for the lights on our tandem.
The wires come out from the battery area and under the frame before going into the fender. That is where I planned to splice. Still don't know what effect it will have on computer or voltage
 

tomjasz

Well-Known Member
Easy for someone handy with wiring to make. And fit with correct connectors. Can be a very clean install @PedalUma for insight.

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fooferdoggie

Well-Known Member
The wires come out from the battery area and under the frame before going into the fender. That is where I planned to splice. Still don't know what effect it will have on computer or voltage
I have replaced both lights after wire damage it would not hurt anything worse can you get a error code if it is too many watts.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
I have replaced both lights after wire damage it would not hurt anything worse can you get a error code if it is too many watts.
That's going to depend on the controller. Some controllers feature light output wires that aren't even fused, and will smoke the controller if overloaded. I WOULD NOT assume it's just going to error out on you.
 

penserv

Member
Region
Canada
City
Calgary, AB
When I put lights on my E-bike, I just made sure to get ones with variable input voltages. As I recall, my tail light is variable from 6-60 V, which works fine for my 52 V system. Then I can just splice the two wires into a 5.5 x 2.1 mm round connector and plug directly into my CA3. Biggest thing is that most lights have a plug-in cable and you either have to glue it in place or modify the light so it is permanently wired in.
 

penserv

Member
Region
Canada
City
Calgary, AB
You can always use a battery operated light or a rechargeable light. Problem is, when you need the light and the battery is dead, you never seem to have the right battery or charging cable handy. You've got a big battery on your bike. Why not use it?
 

Robspace1

Active Member
Region
USA
I have a Trek Allant +7 E bike I use for commuting. I tow a trailer with it and want to add tail lights to the trailer. I want to wire from the existing factory tail light to the two new ones I want to add to the trailer. I want to do it this way so that every time my factory headlight and tail light are on, so are the tail lights on my trailer. I do not want to go the rechargeable remote tail light route because of the inconvenience of having to remember to turn them on as its getting dark on my ride or not knowing if they're actually working because the battery might be dead. What I don't know is: will adding this small load to the tail light interfere with the computer? What is the voltage LED light I would need to purchase?
Thanks in advance for any help
 

Robspace1

Active Member
Region
USA
Make it easy on yourself and get the Bikespark auto sensing tail light. They have the large ones for cargo bikes for 30 bucks on Amazon. Had mine for two years. Work great. They turn off when no motion is made. Come on when you move the bike. 5 modes. Great light. Usb lasts long time.
 

Duneit

New Member
Region
USA
Make it easy on yourself and get the Bikespark auto sensing tail light. They have the large ones for cargo bikes for 30 bucks on Amazon. Had mine for two years. Work great. They turn off when no motion is made. Come on when you move the bike. 5 modes. Great light. Usb lasts long time.
Thanks!!! I bought one I thought had this feature but you have to turn it on each time. I'm going to buy one of these. Thanks again!
 

Robspace1

Active Member
Region
USA
Your welcome. I have one on my escooter as well. They look great at night, but for the brightest daytime tail light nothing beats the Cygolite. They have the brightest head and tail lights out there. An American co., the tail light can be seen for blocks during the daytime! I have two of them on the back. Very adjustable brightness levels and modes and usb recharge. But, not a smart light. You have turn them off and on yourself. Well worth the daytime safety on busy roads.