My biggest complaint with our first-generation Tern HSD P9 was the headlight. The bike came with a Tern Valo, rated at just 150 lumens / 40 lux. It’s a truly terrible light.
I knew we could do better. I knew that Tern could do better. Our GSD came with a Roxim Z3EK Pro specced at 450 lumens / 55 lux low beam and 700 lumens / 213 lux high (Tern calls this the Ignis Headlight). The Roxim isn’t easy to source in the US, so I found Supernova.
I wanted something substantially brighter that would still run directly from the HSD’s Bosch battery, turn on and off with the bike, and ideally add a real high beam. I ended up purchasing a Supernova Mini 3 Pro.
The upgrade
The difference in output is enormous:
| Tern Valo | Supernova Mini 3 Pro | |
|---|---|---|
| Low beam | 190 lumens | 350 lumens |
| Low-beam intensity | 45 lux | 110 lux |
| High beam | NA | 800 lumens |
| High-beam intensity | NA | 140 lux |
The current Mini 3 Pro is rated for 350 lumens / 110 lux on low beam and 800 lumens / 140 lux. It can actually produce 1,100 lumens at 21W on systems capable of supplying that much power, but not on the 12W HSD system.
In normal riding, output goes from 190 to 350 lumens, or about 1.8× the factory light’s output. Hit the high-beam button and it’s 4.2× brighter than the original light.
More importantly, the Mini 3 Pro isn’t simply blasting more light everywhere. Its shaped low beam keeps the light where you need it without dazzling oncoming riders and drivers, while the high beam fills in the area above the normal cutoff.
Parts and cost
The main expense is obviously the light. I purchased the Mini 3 Pro from VPL Bikes in Paonia, Colorado. The light is currently listed at $263 including the mount, high beam switch, and bare cable. Note – the HSD center handlebar diameter is 25.4 mm / 1 inch, not 31.8 mm, so the mount is a little awkward. More on that below.
I also needed a couple of small 2.8 x 0.5mm male blade/spade terminals to connect the Supernova to the HSD’s existing headlight wiring. Purchased on Amazon for $5 here.
Removing the original HSD light
The nice thing about this conversion is that I didn’t need to modify the Bosch electrical system itself or run a new cable through the bike.
The factory Valo Direct is already powered by the Bosch motor’s lighting output. After removing the original light with four phillips screws, I was left with the HSD’s two existing power wires.
Before doing anything permanent, I connected the Supernova’s red and black leads directly to the HSD wiring to verify polarity and make sure the Bosch system could run the light.
One lesson from this part: don’t cut the HSD’s factory connectors unless you have to. I initially considered doing that, but there’s no reason. The existing female terminals can be retained and the Supernova can be terminated to plug into them.
Cut the Supernova cable to a good length and attach the spade connectors to the bare ends. Once the correct terminals are fitted, this makes the electrical installation reversible.
Installing the high-beam switch
The Mini 3 Pro has a separate magnetic high-beam button, placed nearby on the handlebars.
The button mounts on the handlebar within thumb reach. Normal operation gives you the shaped low beam. Pressing the button activates the much brighter high beam. I stuck it near the Bosch display.
Mounting the light
This is the one part of the project I’m still refining.
The included Supernova universal handlebar mount works on the HSD, but because of the HSD’s unusual Tern Andros/Physis handlebar arrangement, the clamp sits to one side of the centerline. The light can be positioned reasonably close to the middle, but the installation isn’t as clean or symmetrical as I’d like.
The Tern GSD has a much nicer solution – the Roxim headlight uses a dedicated bracket that positions the light directly in the center underneath the handlebar/handlepost assembly.
According to Bike Shop Girl’s amazing part list, that’s a Tern part: Light Bracket – Ignis, Handlebar Mount (SKU: F.07004.0026.03.00). I have a call into a Tern dealer to see if I can purchase that separately.
Was it worth it?
Absolutely.
Going from 190 lumens to 350 lumens in normal use is already a substantial upgrade. Having 800 lumens available on demand changes what the bike is capable of at night. It feels safe now! Not just a bike to ride alongside the better GSD.
The upgrade also retains what I wanted from an integrated e-bike light: no separate battery to charge, no light to remember to remove from the bike, and no need to turn it on independently. It’s powered by the HSD’s Bosch system just like the original light. And yes, it can still be turned off by holding the + button on the Bosch controller.
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