Review: Serfas Thunderbolt

It's 40 grams and bright as heck

Lights Lights Shootout

2015 Lights Shootout

Serfas Thunderbolt Front

The Serfas Thunderbolt became one of our favorite lights last year with its small, rechargeable package and serious Lumen power. It’s an LED array that is visible from a very wide viewing angle, making it a perfect ‘to be seen’ commuter light.

This year, the Thunderbolt evolves with a matching tail light and a clear housing for both headlight and tail light versions. The clear housing for the lights transmits the light through the housing, giving extra brightness and more degree angles of visibility.

The tail light version is of course useful, as it allows the rider to be very visible from behind. The unique shape of this light allows it to be attached to almost any part of the bike.

Serfas Thunderbolt on Bike at Night

Of course the light is rechargeable with lithium batteries integrated into the light. The batteries are not very big for a light this bright, so run time is only 1:15 hours at the constant high mode. High Flash mode delivers a decent 4 hours of run time.

Integrating Sphere Measured Lumens

This light measured 82 Lumens in an integrating sphere. Claimed Lumens by the manufacturer is 90 Lumens. The Lumen-hour graph below shows how the light performs over the first three minutes of its battery cycle. Compare all Lumen Tests here »

Serfas Thunderbolt Lumen Chart

  • 40 grams and tiny
  • Really high visibility, especially with the clear housing
  • 80-90 Lumens of actual output is excellent for a light of this size
  • Light is pretty versatile and can be used for other purposes such us a camping light
  • 1:15 in constant High mode is pretty short
  • At this price point, the competition is catching up with much brighter lights with longer run times.
  • Price: $40
  • Claimed Lumens: 90 Lumens
  • Measured Lumens: 82 Lumens (some light leakage in the integrating sphere occurred due to the light’s unusual shape
  • Lumens per $: 2.05 Lumens
  • Lumens per gram: 2.05 Lumens
  • Time on High: 1:15 Hours
  • Charge Time: n/a Hours
  • Mounted Weight: 40 grams
  • Category: Commuter
Overall Rating

4.5 out of 5 Stars

For more information visit

This article is part of Mtbr and RoadBikeReview’s 2015 Lights Shootout. To see all the bike lights tested CLICK HERE.

About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a lugged commuter, ultralight carbon road steed, singlespeed or trail bike. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. This obsessive personality has also turned him into a bit of an addict when it comes to high quality coffee and IPAs.

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  • Greg Jones says:

    I got one three weeks ago. It wouldn’t turn on today. Have to get with Serfas tomorrow, it should be under warranty.

    It worked good, until it didn’t. From car response, it work well on low flash.

  • Greg Jones says:

    I did email Serfas last week. I was returning today to add that I just received my replacement light this morning and have it charging now. It works fine. Serfas customer service was prompt in responding to my complaint and replaced the light without any charges to me.

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