Olight ST25 (XM-L2, 2xAA) review: BEAMSHOTS, RUNTIMES, VIDEO+


May 27, 2006


The ST25 is the latest 2xAA light from Olight - following up on the S15 from last year (which came with a extender battery tube for 2xAA). The ST25 does have a few distinguishing features – most notably, its secondary electronic "stealth switch" in the tailcap.

Let's see how the ST25 compares to the current competition. :wave:

Manufacturer Reported Specifications:
(note: as always, these are simply what the manufacturer provides – scroll down to see my actual testing results).

  • LED: 1 x Cree XM-L2
  • Offers five brightness levels plus strobe
  • 2xAA or 1x14500 (+ battery spacer)
  • Output/runtime: 550 lumens / 0.5hr – 300 lumens / 1hr – 100 lumens / 6.5hrs – 10 lumens / 60 hrs – 1 lumen / 200 hrs
  • Peak intensity: 4,400cd
  • Peak distance: 130m
  • New, flat Stealth tailcap that allows for quiet constant on switching
  • Side switch cycles through three brightness levels and activates strobe and turbo modes
  • Multi-position pocket clip that allows flashlight to be quickly deployed
  • Easily accessible lock-out feature through the side switch to prevent accidental activation
  • From the off position, automatically return to your last brightness level with the built-in memory function or hold for instant access to 1-lumen moonlight mode
  • If your last used mode was strobe, instantly activate with the tailcap switch
  • Instantly access the 550-lumen turbo mode by double clicking the side switch
  • Waterproof up to two meters IPX-8
  • Impact resistant: 1.5m
  • Aircraft-grade aluminum body with anti-scratch type III hard anodizing
  • Stainless steel bezel provides protection from drops
  • Dimensions: 152.5mm x 24mm
  • Weight: 78g (excluding batteries)
  • MSRP: $60



The retail display packaging is identical to the other recent Olight lights (and bears a close resemblance to the recent Foursevens lights). Specs and performance are printed on the clear plastic box. Inside, you get the light with dual-direction pocket clip attached, wrist lanyard, extra o-rings, product insert and manual.




From left to right: Duracell NiMH AA; Olight ST25, S15 with extender; Eagletac D25A2; Fenix LD20; Nitecore MT2A.

All dimensions directly measured, and given with no batteries installed:

Olight ST25: Weight: 76.1g, Length: 152.4mm, Width (bezel): 23.0mm
Olight S15 2xAA: Weight: 59.2g, Length: 137.9mm, Width (bezel): 23.1mm
Neutron 2A (2xAA form): Weight: 73.46g, Length: 146.2mm, Width (bezel): 25.5mm
Eagletac D25A2: Weight: 54.8g, Length 148.5mm, Width (bezel): 21.0mm
Foursevens QAA-2 X (Tactical tailcap): Weight: 60.1g, Length: 149.1mm, Width (bezel) 22.0mm
Jetbeam BA20: Weight: 70.2g, Length: 156.4mm, Width (bezel) 23.2mm
Nitecore MT2A: Weight: 66.9g, Length: 154.3mm, Width (bezel):22.7mm
Nitecore EA2: Weight: 68.9g, Length: 134.4, Width (bezel): 26.1mm
Sunwayman D20A: Weight 118.4g, Length: 102.6mm, Width (head) 20.9mm, Height (head) 35.1mm






Physically, the ST25 is a larger light than the S15 (with 2xAA extender rube). As you can see above, it is within the size range of most 2xAA lights. Overall impression is still similar to the other Baton series lights, however, with black anodizing (matte finish) and bright white labels. Although still without typical knurling, the ST25 shares the same raised checkered pattern as on the S15 and other Batons. With the pocket clip attached, I'd say grip is pretty good.

The pocket clip is comparable to the S15, and seems to hold onto the light fairly securely. I personally like it, as you can clip it on you in either orientation (i.e., bezel-up or bezel-down carry), although it might be rough on clothing given how tightly it fits.

Like the other Batons, the ST25 uses square-cut screw threads (anodized for tail lock-out, like the other Batons). Light can tailstand, and there is a split-ring/lanyard attachment hole on the side of the tail cap as before.

What's new about the tailcap is the secondary electronic on/off switch. This is recessed slightly at the tail, and functions as a reverse-clicky (i.e., press-and-release to turn the light on or off). See my User Interface section for a greater discussion.

Main control of the light is through a side electronic switch, as with the other Baton lights. Switch feel is a bit different though, as the ST25 has a more pronounced "click" to it than the earlier Baton series lights I've tested. User interface has been updated from the earlier models (again, see UI section below).



As with other Batons, the light has a flat stainless steel bezel ring. The o-ring is no longer red (as on the old Batons), but uses the same glow-in-the-dark blue of my recent M18 Striker. Reflector is smooth, and relatively deep. The lens anti-glare coating is also similar to my M18 (i.e., not as pronounced as the old Batons, which tended to introduce some purple/green fringing). :thumbsup:

Scroll down for specific beamshot comparisons.

User Interface

The ST25 has two electronic control switches – a tailcap on/off switch, and a side switch for both on/off and mode-changing.

Turn the light on or off by a click (quick press-release) of the tail switch. You can also turn the light on or off by a single click of the blue side switch.

Mode changing in controlled exclusively by the side switch. When on, press-and-hold the side switch to advance through modes in the sequence Lo > Med > Hi, in a repeating loop. Let go of the switch at any time to select the mode your want. The light has mode memory, and retains the last level set when you turn it off/on.

Double-click the side switch from Off to access Turbo. You can return to the main sequence modes by a press-hold of the switch while On. The is no mode memory for Turbo. Note that you cannot access Turbo through the main press-and-hold sequence, only from Off.

Double-click the side switch from On to access Strobe. Click or sustain-press the side switch to exit strobe mode. Note that there is no memory for Strobe when using the side switch (i.e., you will always need to double-click from On to activate it). However, if you re-activate at the tailswitch after turning off in Strobe, it will re-activate in Strobe.

Press-and-hold the side switch from Off to access Moonlight. You can return to the main sequence modes by another press-hold of the side switch. Memory mode works for Moonlight.

You can lock out the light electronically from Off by continuing to hold down the side switch after Moonlight engages. If you release as soon as Moonlight turns off, the light will be locked out at the side switch only (i.e., the tail switch will still work). To lock out both switches, you would need to hold the switch down for an extra second after Moonlight turns off. Either way, the light will be locked out until this maneuver is repeated. Thanks to the anodized threads, you can also lock out the lights by a turn of the tailcap.

There is an interesting quirk in the interface, due to the secondary tailswitch – you can actually use the light (sort of) like a twisty. When you tighten the tailcap against the body, the light comes on in the last memorized mode – but only every second time. So for example, when On, doing one loosen-tighten cycle of the tailcap turns the light Off (but allows re-activation by a press), while doing two loosen-tighten cycles turns the light Off and then back On.


For information on the lights, including the build and user interface, please see my video overview:

As with all my videos, I recommend you have annotations turned on. I commonly update the commentary with additional information or clarifications before publicly releasing the video.


Like the other Batons, the ST25 is current-controlled at all levels – there no indication of pulse width modulation (PWM) on any mode. :thumbsup:


Strobe is a typical 9.9 Hz fast strobe.

Standby Drain

As the switches are electronic in a nature, a standby current drain is always present when a battery is installed and the tailcap fully connected. Without the tailcap switch in place, I measured this current at 312uA on 2xNiMH. For 2000mAh capacity cells, that would translate into just under 9 months before cells would be drained. Note that I have not measured the current draw with the tailcap in place.

Note that you can always lock out the lights by a quick turn of the tailcap, relative to the body. This will also prevent accidental activation.


For white-wall beamshots below, all lights are on Max output on 2xNiM AA (Sanyo Eneloop). Lights are about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Automatic white balance on the camera, to minimize tint differences.









There are some artifacts in the beam on my ST25 sample – although this doesn't show up in the up-close beamshots above. But at a distance, the hotspot has a defined outer edge and defined bright middle, with a dark ring between them. There is also a noticeable tint shift, with a relatively yellow-green tint to the center hotspot, and cooler white tint to the outer hotspot ring. The spillbeam is a consistent cool white.

Note that this is really only visible on a white wall (but unmistakably there). It is likely an artifact of the exact focusing depth of the reflector on my sample.

Testing Method:

All my output numbers are relative for my home-made light box setup, as described on my flashlightreviews.ca website. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for any extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.

I have devised a method for converting my lightbox relative output values (ROV) to estimated Lumens. See my How to convert Selfbuilt's Lightbox values to Lumens thread for more info.

Throw/Output Summary Charts:

My summary tables are reported in a manner consistent with the ANSI FL-1 standard for flashlight testing. Please see http://www.flashlightreviews.ca/FL1.htm for a discussion, and a description of all the terms used in these tables. Effective July 2012, I have updated all my Peak Intensity/Beam Distance measures with a NIST-certified Extech EA31 lightmeter (orange highlights).



Although the ST25 is rated as "550 lumens" on Turbo, that is definitely misleading. While the light is >550 estimated lumens upon activation in my testing (on 2xNiMH), it quickly drops off in output. By the time you reach the ANSI FL-1 standard of 30 secs post activation, output was ~500 estimated lumens. And after a few mins runtime, you will be down to <400 estimated lumens. See my runtimes below for more info.








The ST25 generally shows quite flat stabilization – except on Turbo, where there is a rapid drop-off in output over the first few seconds to minutes.

Overall output/runtime efficiency is quite good for the class. The ST25 performs comparably to the S15 on Med – but on Hi/Turbo, my S15 was a stellar performer in comparison. The S15 was particularly impressive on Hi on L91 lithiums.

Potential Issues

Turbo is only available from Off (with a double-click), not from the main mode sequence when On.

Turbo output does not last for long – in my testing, you will only have ~550 lumens for a few seconds at most, even on NiMH. Within a few minutes, Turbo output flattens off at a <400 lumen level (i.e., see my lumen tables and runtimes above). You will also need to use NiMH to noticeably appreciate the initial difference from Hi.

Accidental activation is always a potential concern with electronic switches (especially protruding ones like the side switch here). You may want to physically lock out the light at the tailcap when not in use.

The tail "stealth switch" is of limited functionality (i.e., off or on only). However, it does allow Strobe to be memorized (something the side switch does not), and can function as a partial twisty (i.e., every second cycle activates the light).

My ST25 had more pronounced hotspot artifacts than typical in this class (i.e., a well-defined dark ring, with tint shift on either side). This is likely due to the precise depth adjustment of the reflector on my sample.

Preliminary Observations

The ST25 an additional member in the Baton series line-up – and one that offers dedicated 2xAA support. Note however that the S15 also supports 2xAA through the use of an included battery extender.

Build-wise, the ST25 is a bit more substantial than the S15 (although quite in keeping with most of the dedicated 2xAA lights). One thing that stands out is the secondary "stealth" switch in the tailcap. I haven't seen that before. :eek:oo:

The usefulness of the secondary switch for most users is debatable though, given its simple on-off role. I suppose it might appeal to the tactical crowd for its silent operation and Strobe memory feature (although I'm sure they would also have preferred a forward switch mechanism, as opposed to the reverse-clicky like switch used here). :shrug: It is interesting that the tailcap sort of works as a twisty as well (only with every second tightening leading to light activation).

While some may appreciate the additional functionality, it does tend to mean the user interface is a bit complex (with variation in lock-out features, mode memory, etc.). I suspect a number of users are also likely to be disappointed to see that Turbo is only accessible from Off (and without memory). Normally, you would like to be able to switch or jump to the highest output level while the light is actually on. :rolleyes:

Turbo output is quite impressive for this class – the ST25 is actually the second brightest 2xAA light I've tested. However, the rated "550 lumens" is definitely misleading, as the light can only hold that for a few seconds (and then only on NiMH). More practically, I would consider the Turbo mode as a sustained ~400+ lumen level on all cells. As that is not much higher than the regular Hi mode, the loss of Turbo on the main sequence may not be much of an issue after all.

Performance-wise, the ST25 a good example of a current-controlled light, with typically very good stabilization and efficiency on all non-Turbo modes. That said, the S15 (with 2xAA extender) was a stellar performer on its Hi level – on all batteries. :whistle:

Beam pattern is a bit "throwier" than typical for this class, but is still generally well balanced. Note that my sample also had hotspot artifacts, which is likely related to the "throwier" nature (i.e., reflects precise depth adjustment of the smooth and deep reflector).

At the end of the day, the ST25 has a few features that differentiate it from the competition. If these better meet your needs, the ST25 could be a good choice for you. But I expect that most general users would be better served by the S15, with its more versatile battery configurations (i.e., supports 1xAA/14500 in condensed form) and consistently excellent performance on all 2xAA battery sources. :wave:


ST25 was provided by GoingGear.com on behalf of Olight for review.


Jul 22, 2013
Folsom, CA
Thanks for the review selfbuilt. Top notch as always.

This is one of a few lights I've purchased before reading your review. I actually enjoy the silent tail cap for night time use. This has become my go to light around the home if tons of light isn't needed. I would EDC it, but I find 2x AA to be a bit too long for my pockets.


Newly Enlightened
Feb 10, 2012
Good to know my little S15 hasn't yet been dethroned by its own kind!

Really enjoying the S15, extremely capable little light. Am tempted to find a third extender though, just to kick up that battery life when camping and such...