Gearbest kindly sent me this bike light for review.
That doesn’t mean that my review is biased, I’ll be as objective as if I bought the light with my hard earned money.
Presentation
- This is sold as a bike light as well a a head light. It does both well.
- It is sold with a battery pack (2S2P) with a long wire.
- There are two XM-L2 LEDS. One has a deep reflector, sending light far away (thrower) and the other has a shallow one, for close up lighting (flood).
* There are 4 modes:
- Flood LED only
- Throw LED only
- Both LEDs
- Blinky
- A long press will turn the light off.
- There is no lower mode, but that’s OK IMO for a bike light.
- There is no visible PWM.
- The light setup as a headlight weighs about 360g. Most of the weight is in the battery pack (about 200g).
Summary
Pros:
- Nice construction with decent water proofing
- Good user interface with battery indicator
- Decent runtime (2-4h)
- Nice beam pattern
- No visible PWM
Cons:
- Battery capacity is on the low side for a 4 cell pack.
- When used as a head light, the wire between the battery and the light is too long
A few pictures…
The light came in a nice box with a magnetic hatch.
The box contains:
- Light with its non removable cable and water resistant connector
- Head band
- Battery pack with water resistant connector and rubber coating
- Two rubber straps to fix the light to the headband or to your bike handlebar
- Nylon strap to fix the battery pack to the head band or to your bike frame
- Charger (8.4V 1A)
Connector between light and battery pack. Notice the Oring and screw.
The light
The body of the light is made out of aluminium. The anodizing is good and it arrived in perfectly good condition.
To make light, it uses two XM-L2. The tint is cool, if I had to guess I would say the bin is 1A. Each LED has a different reflector. One is deep which produces a tight spot (throw) while the other is very shallow and produces a very wide beam (flood).
* There are 4 modes:
The beam pattern is very (very) floody. Almost like a bare LED without reflector. This mode is useless to light anything faraway. Runtime: ~4h.
The deep reflector has a standard beam pattern for this size. It is very similar to my convoy S2+. Runtime: ~4h.
In this mode the runtime is halved (~2h). It is a nice combination of flood and throw, perfect for a bike light.
- Blinky
About 10Hz and uses both LEDs
A long press on the button in any mode will switch it off. When the light is switched on, it always starts in flood mode. There is no memory.
This is acceptable IMO as it’s much easier to develop memory of the click sequence to go in the mode you want. Also, if you don’t like blinky you almost never have to cycle through it as it is the last mode.
The guts
The light comes appart easily. Two screws on the front and two on the back. There are orings everywhere. The blue ring that can be seen above has an unusual shape. I wonder if it does a good job at stopping water… However the screws are not water tight. Adding some thread locker would probably solve the issue.
- Driver
As you can see, there are two drivers on the same board, one for each LED. There is a controller that enables or disables each driver separately to create modes.
The drivers use a buck topology. (If you want to know more about this, I published a guide with more details here)
The input voltage varies between 8.4V and 6V because the battery pack has a two series (2S) configuration. I tried to feed the drivers with a lower voltage and they kept working fine even at 4V.
The light output is perfectly stable until the last moment where the battery pack protection kicks in. That’s a big plus for me.
Some current readings on the battery side:
1 LED: 0.6A at 8.4V
2 LEDs: 1.2A at 8.4V
I also measured the current at a very low voltage:
1 LED: 2.2A at 3.4V
This is not the normal operation so it is just to show that the driver will increase the input current when voltage decreases to maintain a constant light output.
- Battery indicator
There are three green LEDs next to the switch that indicate roughly the state of charge of the battery. The green LED starts blinking when there is about 5% left in the battery. This is also very useful IMO.
Heat Management
The body is hollow to host the driver.
The LED is properly glued down on a metal ring. I’m confident that the heat transfer is good on that part. However that metal ring is then simply placed on a notch in the body. Once the front part and reflectors are in place and screwed in there is some pressure that maintains a good contact between the metal ring and the body. I don’t know how good the heat transfer is at that point, but I don’t really like it. However I’ve seen much worse and the body heats up quite quickly so at least some heat is transfered. What I would like to see is the LED directly screwed or glued to a thick plate that is part of the aluminium body. For people who don’t care about this, I’ll just tell you that this is not perfect for LED longevity but will work fine.
Reflector and Oring. Nothing to say.
Head strap
The head strap is adjustable in every way possible and I have no complain about it.
Battery pack
When I received it, the battery pack was at 8V. I did a full charge and discharge test and got a capacity measurement of about 2500mAh. This is very bad for a 2S2P pack! That means that each cell has about 1250mAh… As of today a very good cell has about 3000mAh and a cheap one is around 2200mAh. This is a big con for me, they saved a few bucks (less than $4USD) on the batteries but that halved the runtime!!
The battery pack is enclosed in a nice rubber pouch that will probably protect it from rain.
There is no markings on the cells. There is a battery protection circuit board (PCB) under the black heatshrink. The light will run until the protection kicks in.
Once the protection is triggered, the pack won’t allow the light to turn on again until charged for a few seconds.
After the protection stopped the discharge, the battery pack was at 6.2V. This is a good value. The PCB also protects the pack from short circuits.
I measured the total pack resistance (batteries + PCB + cable) at around 0.15ohms. I’m surprised at this value, it is very good.
Charger
The charger came with a US plug. However it works fine with a EU adapter and 230V.
The open circuit voltage is 8.42V which is good for a 2S pack.I don’t know if the PCB inside the battery pack balances the cells.
The charger takes 2-3h to charge a pack.
The LED on the charger is red when charging and green when it’s done.
I’m no expert, but I’ve seen worse. The charger doesn’t get very hot which is a sign of good efficiency.
Final words
Overall I think that this is a very good bike light. It’s also a good headlight, specially with the flood mode which is very useful for close up work.
At a price of $30-35USD it’s a very good value. It’s perfectly usable as is.
For people who like to tinker, you can replace the battery pack to increase runtime (or decrease weight) and try to increase current (just make sure to improve heat transfer before doing that).