Upgraded Radwagon 4 Lighting


New Member
I picked up a new Radwagon 4 this spring since I currently am not driving and needed something that could do everything (on a budget) but I knew from the start that the OEM Spanninga lights would likely be a problem after reading reviews and talking to a friend who had bought a Rad Mini. Sure enough the headlight was almost horrifically underwhelming for a bike that can hit 20mph easily and the town I live in has very sparse street lighting to boot. I had good experience with my Busch + Muller taillight on my manual utility bike and decided to go with their products for both taillight AND headlight.
Now the main confusion I found was on confirming whether the lights would operate on the apparent full 48v current supplied to the Radwagon's light circuits. The IQ-XE was clear enough in its compatibility but the Line K Brake taillight was a bit of a mystery (though now it seems the power rating is on the website clear as day). The challenge was finding a way to rig them onto the bike without cutting the factory harness (I'd reached out to Rad and their official response to my wanting better lights was to get a second handlebar-mounted battery light...so no). I found a company that stocked pigtailed Julet connectors (the snazzy connectors used on the Radwagon 4 and, presumably, other ebikes) and you can find that here. For this project I needed a 2-pin male and a 4-pin male for the headlight and taillight respectively. Some adhesive-lined heatshrink tubing and soldering gear along with a heat gun (or other way of shrinking the tubing) were necessary and you'll also need a multimeter, good conventional wire strippers but also something like this round cable stripper to get through the thick outer insulation of the Julet pigtails. The wires within are a particular pain to strip so give yourself plenty of extra length for trial and error in case your strippers are too tight. If I had to do this again, I'd get a better stripper for the inner wires than the one I had (I ended up having to delicately use the Fluke stripper linked above to cut the insulation from the inner wires).
I don't have a full DIY for this since I wasn't even sure it would work when I started, but here are the general steps:

The headlight installation is the easiest part of this project. The Busch + Muller IQ-XE has a pair of 20 gauge wire leads for its power supply. Basically all you need to do is a little trial-and-error by plugging the pigtail into the factory harness and see which way lights it up and which way doesn't. Once that's done, just make a note of which color wires go with which and then cut the pigtail down. I don't recommend trimming the leads on the headlight itself (nor do B+M) so just bundle the excess out of the way. A more electrically-literate user may step in and correct me on this but I found (after using crimp connectors) that it was easiest to just twist the conductors together in-line, flux them, and solder them clean before slipping heatshrink tubing over them for proper insulation. I do not recommend mounting a light to the accessory front rack even though a mounting hole is provided. If you live anywhere with rough or uneven pavement, it bounces maniacally and is really annoying with a light on it. If you want to do it anyway or you live someplace with good paving, the bracket around the light housing can be rotated 180 degrees. Simply unfasten the bracket arm from the "ring" around the housing and spread the flange where it was bolted. You should be able to rotate the ring now and you'll feel it "click" into place at 180 degrees. If you do NOT do this, the beam will be upside-down and you'll have no light on the road while blinding all oncomers. That said, the IQ-XE has a double-jointed bracket and is compact enough to fit at the fork crown. Be aware that you may want to measure and get some right-sized washers for mounting the headlight as the fender-mounting bolt's head is not wide enough and the washers that Rad supplies are too wide. First time I tried to install it I ended up sinking the bolthead INTO the headlight bracket!

This took a while longer (mainly because I honestly don't know how to use a multimeter beyond checking for continuity). Because the taillight has a brake light function, you have to determine which wires do what. With two pairs, one carries the power and the other carries the signal for the brake light function. I believe the way I found the power circuit was to check continuity with the bike powered on, as the circuit opens when it's off. The light will ONLY light one way and if you test the system without the brake signal leads connected the self-diagnostic the bike does on startup will trip and the headlight will go off after a second. Presumably the internal conductors on the Julet pigtails are the consistently-colored so if this is the case, i'll just give you the wiring guide. Also forgive me but I'm slightly colorblind so I'll do my best.
For the taillight, the brake circuit is the black and the blue-green pair in the Julet pigtail. I wired them as Blue/Green->Black/white (+) and Black->Black (-). The Main power to the taillight itself is provided by the red and yellow/green wires in the Julet pigtail. Red->(+) and Yellow/Green->(-). Obviously test everything before soldering and make sure you have your heatshrink tubing ON THE WIRES before soldering so you can slide it down and over the soldered connection (if it's not clear, you cannot get tubing onto wires that you've already soldered, haha)


You can see here how hectic the experimentation process was to get the taillight wiring correct


Here you can see the inner wires of the Julet pigtail on the right. The clamp/prong contacts on the right are the power input whereas the brake signal is supplied to the leads on the left.


You can see how tight the clearance is. I wasn't able to fit the included reflector so I mounted a large round one to the front of the crate that's bolted to the front carrier. Make sure you leave enough slack so that the wires don't go taut with the handlebars all the way to one side or the other. That said you also don't want the wire rubbing on anything or it can wear down the insulation over time.


Here's a pretty accurate depiction of how powerful this headlight is at 150 lux. I don't recommend any headlight that's rated in lumens simply because lux actually measures the effectiveness of the light as opposed to the raw, total output. For example, I had a 1600 lumen Cateye rechargeable but it was a huge waste because it didn't have a shaped beam like this and therefore had to be aimed downward, wasting a large amount of that light (note that the light in the picture above isn't "brighter" closer to the bike and is instead roughly uniform, just like modern LED car headlights). You want a shaped beam, not a spot/flood light. You can see the cutoff on the fence very close to the ground.


The finished product with clarijs XXL 65-70L panniers. For anti-theft reasons I popped holes in the material that goes over the carrier so i could bolt the 'surfboards' down through the bag material, clamping it in place. These are JUST wide enough to fit the Radwagon's rear carrier. Other mods include a Hexlox antitheft skewer for the front wheel and Hexlox seatpost kits (Qty 2) along with Hexlox inserts for the seat clamp and the stem. The only thing I couldn't secure was the M12 rear axle, though I found a company that makes a possible solution (bulk orders only sadly)

(and for the hawk-eyed among you, yes that's a Sony SL-5000)


Active Member
Nicely done! I'm to lazy to upgrade my lights. I purchased the upgraded headlight for my 'Runner and it wasn't much better than the OEM light. Now I'm gonna look thru your pictures some more in regards to the tail light upgrade. I may break my laziness cycle for an upgraded tail light. Thanks again for the write-up!


New Member
Clearwater, FL
Great mod, Dragon. Thanks for posting this very detailed description.
I’ve done several mods successfully to my Radcity, with the remaining exception of the headlight.
I’ve used a split “Y” Juliet cable to install a pair of stock headlights to double the output, clean and easy but it is still underwhelming. I tried a very powerful Juiced Bikes headlight $50, but my Radcity can not power it nor a third party KT controller either.
So I’m surprised that you managed to power that bright headlight with the stock Radwagon controller, assuming is the same as the Radcity.
Photographs can be deceiving since the output will look brighter than in person, if a long exposure has been used.
As a brightness ”reference” I know that the Rad LCD display is not that bright, so I assume this new headlight is not as bright as is shown in the pictures.
Did you compare this new headlight with the stock? Just confirming.
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New Member
On "Facebook Rad Power Bike Upgrades" group, there's a member (Matthew Lee Newell) who makes plug-and-play upgraded headlights. They're supposed to be compatible with factory controllers, as well as upgraded Bolton controllers.


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