Serfas TSL-2500 Bike Headlight—Top-of-the-Line Power

Serfas TSL-2500 Bike Headlight—Top-of-the-Line Power.

This is a complete package with everything you need to equip your bike with maximum night vision.

Bike lights come in many shapes, sizes and intended purposes. We have them all. Some are just designed to let you be seen, some letting you see the road. When it comes to this Serfas TSL-2500, you will see the road better than ever before. This light opened my eyes to what is really possible when it comes to a well designed bicycle lighting system.

Lumens is a word that is used to measure light output. Sometimes the numbers are fudged, there are articles you can read on how the real numbers stack-up. Serfas has tests to confirm their output, so when they say 2500 lumens I believe it. What I also believe is that this is the brightest, best focused bike light I have tested or had experience with. We have gotten by fine with 650 lumen lights we normally use at mid-power, so with all four levels of power on this TSL-2500 above that, you can imagine the safety it offers.


Out of the box, ready to light your way

Like most modern lights nowadays, the switch controls a electronic circuit. The plus there is to turn it off, you don’t need to toggle all the levels, you just hold the button for a couple seconds. If you do toggle it, it switches between four levels. Max is 2500 lumens, called overdrive. This is way bright, but may be needed by the fastest off-roaders and road bike types. Your other levels output at 1600, 1000 and 600 lumens.

The plastic cased lithium battery sports 6600 mAh, enough to power the light at the low setting for 7 ½ hours, a longer night ride than I’m accustomed to. In overdrive it pumps power for 1 hour and 45 minutes, 2:45 on high and 4 hours on medium. These are some awesome run times compared to the many lights we have and I have tested. An included smart charger will fill the battery back to full in 4 hours or less.

The battery has some other cool and useful features. A USB port will power phones, bike sound systems and recharge digital cameras. There is a low-power warning light that will blink to tell you it is time to recharge, (the headlamp power button does the same at 20% power left) A strong Velcro mounting strap will hold it on your bars or on the frame. I would think it could be placed in a bag too. The end pieces of the case are silicone (?) to keep it from coming loose or scratching your bike. The two power ports have plug covers to keep debris out. The plugs snap in with a sealed feel.

With many mounting options for the battery, I chose this for some quick testing. The light’s handlebar mount is easily adjustable for different sized bars.

The light itself has an aluminum alloy inner housing covered with durable nylon. Built-in are ram air cooling ports to keep the whole unit within temp requirements. Even though LED lights use minimal energy and stay fairly cool, at the higher settings the heat will build. Serfas recommends keeping the light shut off when the bike is stationary to prevent heat build-up, but from my time with this light I would think that is only needed at the higher settings. The light will power down to a lower output level when the heat is too high, to protect itself.

This Serfas light I am testing is the limited edition model. That translates to the interesting color combo. The ones I saw on-line come in black only. Also this light came with a great carry case to hold all the extra pieces it comes with. And when I say it comes with all the extra goodies, I mean it From what I can tell though, all the specs and performance attributes are the same with the standard model.


From the business end, you can see the four LEDs and the cooling slots. Weighing 19 oz, that is a small weight penalty to pay for so much road lighting power.

Along with the light, battery and charger are many other pieces. It comes with a solid, quick and easy to use handlebar mount. A helmet mount is also in the package. I really like the remote button. It Velcros right by your thumb on the bars to make operating the light easy with both hands on the grips. The light will respond to the button on top of the unit or the remote. The included 1 foot and 3 foot extension cords makes battery placement your choice, not the light’s.

One piece I was sorry not to get (yet?) is the optional rear light. There is a place on the main cord to plug it in. The info for that light makes it sound like a very desirable piece to get when you purchase your own TSL-2500. It will stay on steady or flash depending on which power level the headlamp is in. The taillight will reduce the battery run times slightly when used, but not much. The instruction shows the numbers.


Not the best photo, the video I took might give you a better idea of the Serfas TSL-2500 light beam.

All that aside, let’s talk light. Of course I was impressed by the light output, but there is much more to it than that. The wide beam it puts out made riding at night more pleasant. At each of the power settings the amount of light thrown to the side is generous. Some lights with their pencil beam focusing don’t allow you full vision of the road. Not a problem with this Serfas light.

Some of the high powered lights I’ve used are too strong for your fellow riders and oncoming vehicles. I would constantly turn them downward to keep that in check, to the point I wasn’t lighting my own way anymore. I loved the massive light, but what good was it to use it to light your front tire? I didn’t find this to be the case with the TSL-2500. The wide beam is fairly gentle on the eyes of others. Every aspect of this bright light was to my liking and that of my fellow riders.

It easily goes on the bike, making it simple to transfer from one bike to another, something that is important to me. Being such a pricey light, being able to take it off when parked makes sense too. I usually try not to walk away from my bike when parked, but I have lost cheapo lights I wasn’t that concerned about when leaving my bike locked but unattended.
So there you have it. An awesome light, a major investment and the best of performance. When you get the best you expect the best in return. That is exactly what I found with this Serfas TSL-2500—the best right down the line.

Riding at night is fun and peaceful, go out and do it, Turbo Bob.

“Tens of thousands who could never afford to own, feed and stable a horse, had by this bright invention enjoyed the swiftness of motion which is perhaps the most fascinating feature of material life.”—Frances Willard, How I learned to Ride the Bicycle.

Links to Serfas on-line and Facebook

Two videos I took of the light. The first shows it and the pieces. The second is a nighttime riding video.


About Turbo Bob's Bicycle Blog

E-bike Enthusiast Vintage Bike Enthusiast
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3 Responses to Serfas TSL-2500 Bike Headlight—Top-of-the-Line Power

  1. Goodbikegear says:

    There headlights are really cool and I would love to have them on my bike but I need Road Bike Mud Guards which has the stands for the same.

  2. armadillozack says:

    I really like this light, and I would like to know how to get my hands on a Special Edition TSL – 2500 For my new ride, because I have not bought one as of yet and the bike is almost built and on it’s way to me…? I particularly like the fact that it is white because it will look great with my painted bike, because they are one and the same color…!


    • According to Serfas’ Facebook page, they only made 6 of these lights in this color. The final one was given away through their site a couple months ago.
      I would check with Serfas directly to see where you stand. I think I read they were considering another run of the white ones.
      Thanks for reading along. Good luck, Turbo.

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