These lights are USB-powered and use micro-LED strips rather than bulbs. Let me tell you – the LED strips are BRIGHT!! It hurts to look at them even obliquely. This is both a positive and a negative. It’s a positive because you get around 180 degrees of visibility from each light – way more than you typically get from either headlights or taillights, and it gives a degree of confidence that you can be seen from the side nearly as well as from the front or rear. The negative? Well, you can’t mount them quite everywhere you might want to without getting blinded! Despite the brightness, these are definitely more in the “be seen” than “see” category of lights – they don’t light up enough road/trail to function in that fashion, but that’s OK since it’s not what they were designed for. I liked using them in tandem with a brighter headlight, and mounting the Thunderbolt to my fork. However, I couldn’t do this with every bike, since on some of my bikes the structure of the fork meant that a decent bit of the light actually went back up into my eyes! Not really a fault of the light – but a note for those who might be thinking of using a light in that fashion!
The lights are encased in a silicone rubber body with straps that allow quick attachment and detachment to/from just about any part of your bike. I initially thought they might not last very long, but so far the only thing that’s happened is that the (white) models I received are no longer white, and the little flap that covers the USB charge port is a little loose (not a big deal, since that bit sits pretty tightly against the bike frame/handlebar/etc). The flexibility of being able to put a light pretty much wherever I want is AWESOME. I don’t know why more light manufacturers don’t use this method. I’ve attached the lights to bars, forks, seat stays, racks, and a trailer. No problems with them staying anywhere! Once attached they stay put.
According to Serfas, “burn” time is “1.75 hours (high beam); 7 hours (low beam); 3 hours (high blink); 9.5 hours (low blink).” My experience would indicate that these numbers are a little on the high side, but I can’t say for sure as I often wasn’t running them totally in a single mode for a single use (I definitely never used them on low blink for 9.5 hours). I DO know that the front has run out in under 1.5 hours of total use (two 45-minute trips in the dark, separated by about 2 hours). Similarly, I think the other modes run out in a bit less time than advertised. The only one where I’d say this is a true negative is with the high beam for the front. Most of the time, that’s the mode I want it in – and since I do ride for longer periods at night, it’s possible for my ride to last longer than the battery. I’d also say that for anyone who is not commuting to a destination where a friendly USB charger awaits, this might be a little short for longer there-and-back-in-the-dark commuting. However, it probably will cover 90% of potential users just fine.
The on/off button also functions as a mode switch (short hold to switch modes, long hold to turn off). Pretty standard commuter light function, and I never had any issues. The only (slight) beef I had with the switch is that it’s a little tough to manage in winter gloves – on multiple occasions I had to remove a glove to turn a light on. Those of you in warmer climes (or who are only fair-weather riders) won’t be bothered by this.
TL;DR summary: the Serfas Thunderbolt lights are a solid set of be-seen lights that offer unparalleled side visibility and impressive brightness for their size. Run times may be on the shorter end, but the attach-anywhere flexibility brings the Thunderbolt solidly into the “good buy” category.
Please click here to read our review disclaimer as required by the Federal Trade Commission.