M Photon ReX Review
by Roger Caffin and Rick Dreher, with contributions from Will Rietveld
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Flashlight progress comes in unpredictable spurts, interspersed with long plateau periods where little notable progress occurs. The first generation of LED lights used several batteries and a current-limiting resistor. The second generation used several batteries and a fairly crude electronic chip to provide current-limiting. The Freedom chip used in the ReX is a third generation device that is somewhat more sophisticated - and it shows.
Slightly larger than their existing Photon line of button-cell flashlights, the ReX differs in three significant respects: its battery is a single rechargeable lithium-ion cell, it has four (instead of the usual one) good white LEDs, and the ReX can be recharged on the go using common inexpensive batteries.
The ReX is fitted with the LRI Freedom controller chip. This chip is reportedly also used in the LRI Photon Freedom Micro single-LED light, but that unit does not have the recharging facility. The battery in the Photon Freedom Micro unit is replaceable, while the battery in the Photon ReX unit is not. The Freedom chip delivers "stepless" variable output and a number of flash modes as well, all operated via the single button. The button is phosphorescent, by the way, making the ReX a little easier to locate in the dark. A spring clip connected to the ReX with a split-ring gives one a way to anchor the little flashlight to hopefully keep from losing it.
The ReX is charged by connecting to a battery (1.2 volt to 3 volt, see below) using a pair of magnet-tipped wires. The wires are anchored to a yoke that connects magnetically to the ReX itself, and the other ends attach to the donor battery terminals. To keep the positive and negative separate, one yoke terminal has a small plastic collar to prevent it from being reversed inadvertently, creating a polarized connector. This is where several of us had some problems: a mismatch in the dimensions of the polarized connector can actually prevent a connection from being made. At the very least, some fiddling is required to seat the yoke correctly and complete the circuit. Proper connection is clearly signaled by a slow flashing from the ReX, which ceases when charging is complete (in approximately two hours with a fresh battery, according to LRI). This is further discussed under the 'Problems' section at the end of this review.
The Freedom chip does far more than just control the flashing, however. It is a fairly sophisticated switch mode controller chip, and actually performs four distinct functions:
- Sensing the button to turn the power on and vary the power level
- Converting the four volts from the little cell to a variable mark/space ratio supply to drive the four white LEDs at varying power levels
- Converting the incoming battery voltage to the required voltage to recharge the internal cell
- Monitoring the charging process and turning it off when the cell voltage is high enough
It is, therefore, far more sophisticated than the more common chips found in other LED headlights, which just turn the LEDs on and off at three different brightness levels. This is clearly a third generation device.
LRI claims two full charges from an alkaline AA battery and twenty or so full charges from an alkaline D-cell battery. They champion the use of NiMH rechargeable cells for the least expensive and most environmentally friendly approach (with an average three charges from an AA cell). The ReX onboard Li-ion battery is claimed to have a useful life of three hundred to five hundred charge cycles.
The little charge wire assembly comes with a snap connector that can (and should!) be anchored in some safe place to prevent its loss - it's hard to envision fashioning temporary connectors from stray or salvaged bits you might have in your pack! The ReX is too small to store the wires on board, unlike the rechargeable Aquastar mUV, for instance.
Interestingly, the ReX isn't water-resistant, despite not having a battery door. It may be they weren't able to sufficiently seal the two halves of the clamshell around the four-LED bezel to supply this desirable trait, which is a shame, since the Freedom is splash-proof. However, it seems likely that a few splashes would not do much harm to the unit. The ReX ships with a clip similar to that of the Freedom's for attaching to a hat, etc. (ReX accessories, including a clip, headband, and solar charger, are promised in the future.)
At the time of writing this review, the LRI website was claiming that "The ReX will charge from any standard battery of six volts or less." This is not strictly correct and should not be followed. Previously, the website was claiming a maximum of three volts, which is correct. The six volt claim relates to charging from a USB connector, but the supply on a USB connector has a protective ten ohm resistor in series, and this reduces the output to under three volts when used to charge the ReX. Our understanding is that a USB charger is planned for the ReX in the future, along with a solar panel.
However, in bench testing, we were sometimes unable to get the charging circuit to start working when the incoming voltage was much above 2.5 volts. The microprocessor is a shade cautious about overload. On the other hand, we found it would work at very low incoming voltages, down to almost 0.6 volts, which approximates a very flat single alkaline cell, which is actually more important.
- Basic Performance
- In the Field
- Rick's Experiences
- Roger's Experiences
- Laboratory Testing
- Recharging - Basics
- Recharging - Experiments
- Choice of External Battery
- Problems when Recharging and Recovery
- Enhancements for the Dedicated Ultralighter
- Specifications: Manufacturer:, Year/model:, Battery:, LEDs:, Battery life:, Weight:, MSRP:
- What's Good
- What's Not So Good
# WORDS: 5560
# PHOTOS: 12
# TABLES: 1
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