Sofirn BS01


Brand/model Sofirn BS01
LED HP50.1 6000-6500K
Maximum lumens 2,000 lm
Maximum beam intensity 19,233 cd
Maximum throw 277 m
Battery Built-in 21700 Li-ion
Onboard charging Yes (USB-C)
Power bank Yes (USB-C)
Material Aluminium
Modes 4
Blinkies Strobe
Reflector Smooth
Waterproof IP65
Review date December 2023


The Sofirn BS01 is a relatively affordable Smart Bike Light with a built-in 21700 cell, USB-C charging and a power bank feature.

What makes it smart? It can automatically turn on when a bike moves and it can automatically turn off after thirty seconds of inactivity. This feature can be turned on or off.

Here is a video demonstrating the Sofirn BS01:

Sofirn kindly sent this torch for review. I have not been paid for this review nor have I held back my opinions of this torch.


The Sofirn BS01 comes in a white box. An outer cardboard sheath has an image of the torch while a white box inside has a flap that can be lifted to reveal the torch.

Sofirn BS01 packaging Sofirn BS01 packaging

Sofirn BS01 packaging Sofirn BS01 packaging

The following was included in the box:

  • Sofirn BS01.
  • USB-A to USB-C cable.
  • Mounting strap.
  • User manual.

Sofirn BS01 packaging Sofirn BS01 accessories

Sofirn BS01 user manual

Torch in use

The Sofirn BS01 is simple to attach to a bike and easy to use.

Sofirn BS01 in use 1

There is a big rubber button with a battery status indicator. It can be held to turn the torch on and off, or clicked to change the brightness.

I found the High mode to have the right balance between lumen output and runtime while cycling at night.

There is a power bank feature that could be used in a pinch.

Build quality

The Sofirn BS01 is made of aluminium and it has a black anodised finish. There are no sharp edges.

Sofirn BS01 left Sofirn BS01 right

The adapter under the torch clicks into the strap. The torch can be swiveled from left to right and up and down slightly to get the best angle.

Sofirn BS01 closeup-charging Sofirn BS01 strap

The USB cover feels strong but I wish that it had a design like the Sofirn Q8 Plus so that it is easier to replace if it gets damaged.

The plastic lens came with some protective film that needed to be removed before using the torch.

Sofirn BS01 protective-film Sofirn BS01 tail

There are four screws holding the tail plate in place. I used a T5 torx bit to remove the screws. Sofirn advises against removing the battery.

Sofirn BS01 teardown

The tail plate has had some anodising removed in the screw holes and the screws have had a bit of anodising removed under the head of each screw. The threads look as though they have black anodising.

This is the first time that I have seen screws being used in a circuit for a torch.

The torch appears to have reverse polarity protection to protect the driver but the battery might explode if it is inserted backwards. The battery shorted when I put it in backwards and connected probes from a digital multimeter between thenegative end of the battery and the screw hole in the case. Don’t try this at home!

This definitely seems like a budget torch.

LED, bezel, lens, reflector and beam

The Sofirn BS01 has a cool white HP50.1 6000-6500K emitter, a reflector and a plastic lens designed for cycling.

Sofirn BS01 closeup emitter Sofirn BS01 closeup-reflector

CCT, CRI, and duv

I have taken Correlated Colour Temperature (CCT) and Colour Rendering Index (CRI, RA of R1-R8) measurements with the torch positioned two metres away from an Opple Light Master Pro III (G3).

The CCT is around 6700K. The CRI is around 72.

The Delta u, v is slightly negative (rosy) but there is a hint of green near the upper part of the beam.

The beam produced is like a big square with an upside down trapezoid near the top. The trapezoid part of the beam reaches far and it cuts off to avoid blinding oncoming traffic.

Mode CCT (K) CRI (Ra) x y Duv
Low 6729 72.1 0.3106 0.3172 -0.0019
Medium 6707 71.9 0.3108 0.3180 -0.0016
High 6781 72.2 0.3098 0.3164 -0.0019
Turbo 4392 50.3 0.3718 0.4044 0.0151

Calculate Duv from CIE 1931 xy coordinates

Dimensions and weight


I took the following measurements using a digtal caliper.

Measurement Unit (mm)
Length 112.69
Head width 31.76
Head height 27.88
Mount diameter 24.69
Mount max width 28.28


I took the following measurements using a digital scale.

Weight Unit (g)
Torch 155.96

User interface

The Sofirn BS01 has an electronic switch on the top with an indicator light.

There are four main modes: Low, Medium, High and Turbo. And one blinky mode: Strobe.

State Action Result
Off Click Battery status indicator displays for 5 seconds
Off Hold On (memory)
On Hold Off
On Click Cycle (Low, Medium, High, Turbo)
Any Two clicks Strobe
Off Three clicks Activate smart mode
Off Five clicks Activate smart mode and Strobe
Smart mode Hold Deactivate smart mode
Smart mode Click Cycle (Low, Medium, High, Turbo)
Smart mode Two clicks Strobe
Smart mode Three clicks Deactivate smart mode

Smart mode

The indicator light will turn blue when smart mode has been activated.

Sofirn BS01 closeup-blue

The light will automatically turn on when it is moving (i.e. the bicycle is moving).

The light will automatically turn off after thirty seconds of inactivity when the light is idle and not moving.

The button can be clicked to cycle between Low, Medium, High and Turbo or double clicked to access Strobe while in smart mode.

The light will flash three times to indicate that the light is no longer in smart mode after clicking the button three times.

Mode memory

Mode memory includes: Low, Medium, High and Turbo.

Strobe is not memorised.


Strobe appears to have a frequency of 1 Hz.

Battery level indicator

The indicator LED in the switch will display the following for 5 seconds when the torch is on:

Colour Battery level
Green Capacity ≥ 50%
Red 25% ≥ Capacity < 50%
Red flashing Capacity < 25%

Sofirn BS01 closeup-green Sofirn BS01 closeup-red

Low voltage protection

The torch has low voltage protection.

I tested low voltage protection by connecting the torch to a bench power supply and then by lowering the voltage from 4.2V to 0V for a 21700 Li-ion cell.

Mode LVP? Cut-off voltage Current
Low Yes 2.78V 0 A
Medium Yes 2.78V 0 A
High Yes 2.79V 0 A
Turbo Yes 2.81V 0 A


I did not notice any visible PWM (flickering).

What I like about the UI

It is easy to cycle between modes (Low, Medium, High, Turbo) with one click.

What could be improved

  • A lock mode would be nice for storing the torch in a backpack.
  • Double click should be used for Turbo instead of Strobe.
  • Triple click should be used for Strobe.
  • Four clicks should be used for a lock mode.
  • Five clicks should be used to a smart mode.

Batteries and charging


A flat top 21700 cell with a blue wrap was found inside the torch.

Sofirn BS01 teardown

I measured a capacity of 4768mAh by discharging the cell at a rate of 1A using a Vapcell S4 Plus.

I was previously riding around with a headlamp mounted below the handlebar and a regular torch mounted over the handlebar so that I could see up close and in the distance.

Prior to going down the rabbit hole of flashlights, I was using regular bike lights from a local bike shop from brands like Cygolite and Moon Sport. I managed to get about 2-3 years of use out of them before the built-in battery failed.

Cygolite have a repair service but it is not cost effective if you live outside the USA. But I digress.

It is nice that Sofirn have used a standard 21700 cell. But be careful if you replace the battery! It needs to be inserted correctly.


Sofirn BS01 closeup-charging

Power supply: PinePower Desktop USB-A
USB Meter: AVHzY CT-3 (recommended by LiquidRetro)
Room temperature: 21 C

Sofirn BS01 charging profile

Charging completed after 2 hours 30 minutes. The indicator light went from red to green when charging finished.

Sofirn BS01 closeup-red Sofirn BS01 closeup-green

Power supply compatibility

I tried the following power supplies with the built-in USB-C charger:

Power supply USB Type Protocol Does it charge?
Apple 61W Power Adapter USB-C PD Yes
Google Pixel Power Adapter USB-C PD Yes
PinePower Desktop USB-C PD Yes
PinePower Desktop USB-A QC Yes
PinePower Desktop USB-A Yes

USB-C to USB-C charging works.

Power bank

I was able to use the Sofirn BS01 to charge my phone. The charging rate was approximately 5V 1.4A.


Specifications from the user manual:

ANSI/NEMA FL1 Low Medium High Turbo Strobe
Output (lumens) 50 150 500 2,000 500
Runtime 38h 14h 3.5h 3h
Beam Distance (metres) 47 86 156 277
Beam Intensity (cd) 558 1,842 6,075 19,233

Lumen measurements

I measured the current at turn on using a bench power supply.

Mode Specs Amps at start Lumens @turn on Lumens @30 sec Lumens @10 min
Low 50 0.15 A 46 44 44
Medium 150 0.46 A 130 127 122
High 500 0.91 A 387 378 363
Turbo 2,000 3.48 A 1,515 1,367 402

The lumen output is lower than expected. I suspect that this could be due to the 21700 cell and the design of the torch where the four anodised screws the tail form part of the circuit.

I would prefer the following mode spacing:
Low (100 lumens), Medium (400 lumens), High (800 lumens), Turbo (2,000 lumens).

Standby drain

191.6 µA

The 21700 cell might last 2 years and 10 months while idle inside the torch.

I measured a current of 1.96 mA using a UNI-T UT139C digital multimeter by connecting one probe to a screw hole and another probe to the 21700 cell.

I thought that the driver might be defective but an engineer at Sofirn clarified that the torch will hibernate after five seconds if I use the torch and turn it off.

I clicked the button once so that the battery status indicator turned on momentarily. The current peaked at around 4mA and then it dropped to 191.6 µA after five seconds. The engineer was right!

I figure that this is worth mentioning if you are trying to measure standby drain at home. A torch might not sleep until it has been used at least once after reconnecting the battery. The risky part here is that a 600mA fuse could blow in the digital multimeter if I turn the torch on while trying to measure microamps. Fortunately the BS01 has a battery status indicator that can be activated by clicking the button without needing the main emitter to turn on.

The user manual states that the standby current is less than or equal to 100 µA.

Runtime graphs

I used my own DIY lumen tube with a TSL2591 sensor and forked bmengineer’s project RuTiTe to record runtimes.

Note: Lumen measurements may be off by 10% with my DIY lumen tube.

The room temperature was approximately 21 C.

Sofirn BS01 runtime graph

Sofirn BS01 first 3 hours runtime graph

Sofirn BS01 first 10 minutes runtime graph


Here is a summary of the runtime results:

Mode User manual Runtime Turn off
Turbo 3h 3h 11min 24s 3h 12min 23s
High 3.5h 5h 25min 46s 5h 25min 46s
Medium 14h 17h 8min 35s 17h 8min 35s
Low 38h 38h+ 38h+

“Runtime” is the time until the output reduces to 10% of the output at 30 seconds (as per the ANSI/PLATO FL1 2019 Standard).

“Turn off” is the time until my DIY lumen tube no longer detects more than one lumen.

“+” indicates that the light remained on after recording had stopped.

The runtimes results are better than expected.


I took lux measurements with a UNI-T UT383BT at 30 seconds. Each mode was measured at five metres.

Mode Specs (cd) Specs (m) Candela measured (cd) Distance (m)
Low 558 47 425 41
Medium 1,842 86 1,475 76
High 6,075 156 4,725 137
Turbo 19,233 277 16,875 259

The beam distance is slightly lower than expected.


I went to a local park and aimed the Sofirn BS01 at a tree 70 metres away while using Turbo.

Beamshots were taken using a Sony RX100M2 using 3.2", f3.2, ISO 100, 5000K WB.

Sofirn BS01 (Turbo)

Sofirn BS01 Turbo beamshot


The Sofirn BS01 is a good budget bike light.

I have removed an Armytek Wizard C2 Pro Nichia headlamp and a Mateminco FT01 torch from my bike. I am going to continue to use this Sofirn BS01 bike light. It does the job of two torches by producing a floody beam near the bike and by producing a throwy beam so that I can see up ahead while cycling fast.

The runtimes are better than expected but the lumen output is lower than expected.

I would prefer the following mode spacing:
Low (100 lumens), Medium (400 lumens), High (800 lumens), Turbo (2,000 lumens).

I love how Sofirn used a flat top 21700 cell. I can replace the battery in a few years instead of having to throw out the light. Sofirn advises against removing the battery but I would prefer to fix my own equipment instead of throwing it out.

I can highly recommend this bike light.


  • Good runtimes.
  • Practical beam.
  • Strap fits thick handlebars.
  • Power bank.
  • Low voltage protection.


  • Lumen output is lower than expected.
  • Mode spacing.
  • Beam distance is slightly lower than expected.


The Sofirn BS01 is US$31.99 from

Product page

Sofirn BS01 at Amazon
Sofirn BS01 at

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