Sofirn BS01⌗

Specifications
Introduction
Torch in use
Build quality
LED, bezel, lens, reflector and beam
Dimensions
User interface
Batteries and charging
Performance
Beamshots
Conclusion
Price
Product page

Specifications⌗

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

Introduction⌗

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.

Packaging⌗

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.

The following was included in the box:

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

Torch in use⌗

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

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.

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.

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.

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.

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.

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⌗

Dimensions⌗

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

Weight⌗

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.

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⌗

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%

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
Low	Yes	2.78V
Medium	Yes	2.78V
High	Yes	2.79V
Turbo	Yes	2.81V

PWM⌗

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⌗

Battery⌗

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

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.

Charging⌗

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

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

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.

Performance⌗

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.

Runtime⌗

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.

Throw⌗

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.

Beamshots⌗

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)⌗

Conclusion⌗

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.