Acebeam H40 Headlamp Review

Acebeam H40 Headlamp Review

The Acebeam H40 is an AA headlamp which also runs on a 14500 cell, with high CRI output from the Luminus SST-20 emitter. Read on!

Official Specs and Features

Here’s a referral link to the Acebeam H40 Headlamp product page.


Just one body is available, but that body can be had in two emitter choices.  They are CREE XPL HD 6500K or Luminus SST-20 4000K CRI 95+ LED (which I have here.)


This light has a MSRP of $34.90.  That’s a very compelling price for all that this light offers!  Buy it at!!

Short Review

This is a neat little light.  I like in particular that it’s available with 95+ CRI.  Also useful is support for all AA-sized cells, including NiMH and Li-Ion (14500).

Long Review

The Big Table


Acebeam H40 Headlamp
Emitter: Luminus SST-20 (4000K 95 CRI)
Price in USD at publication time: $34.90
Cell: AA
Turbo Runtime High Runtime
LVP? Yes
Switch Type: E-Switch
Quiescent Current (A): ?
On-Board Charging? No
Claimed Lumens (lm) 180
Measured Lumens (at 30s) 164 (91.1% of claim)^
Claimed Throw (m)
Candela (Calculated) in cd (at 30s) 100lux @ 3.422m = 1171cd
Throw (Calculated) (m) 68.4^
All my Acebeam reviews!


Acebeam H40
Emitter: Luminus SST-20 (4000K 95 CRI)
Price in USD at publication time: $34.90
Cell: 14500
Turbo Runtime High Runtime
LVP? Yes
Switch Type: E-Switch
Quiescent Current (A): ?
On-Board Charging? No
Claimed Lumens (lm) 600
Measured Lumens (at 30s) 602 (100.3% of claim)^
Claimed Throw (m) 106
Candela (Calculated) in cd (at 30s) 89lux @ 5.198m = 2405cd
Throw (Calculated) (m) 98.1 (92.5% of claim)^
All my Acebeam reviews!

^ Standard measurement disclaimer:  I am an amateur flashlight reviewer.  I don’t have $10,000 or even $1,000 worth of testing equipment.  I test output and such in PVC tubes!!  Please consider claims within 10% of what I measure to be perfectly reasonable (accurate, even).

What’s Included

  • Acebeam H40 Headlamp
  • Headband
  • Spare o-rings (2)
  • Manual and paperwork

Package and Manual

Acebeam ships this light in a display-ready slip fit box.  Inside the box is some foam, holding the pieces very carefully.  The back of the box is very informative, including output and runtimes for both emitters and 3 supported cell types.

The manual is good.  It includes the UI, and also all of the info from the back of the box, and warranty info, etc.


Build Quality and Disassembly

This is a tiny little headlamp!  There are a lot of ridges on the body, including some cooling fins directly behind the emitter.

One end of the light is thread locked closed.  The other is labeled Open/Close and that’s the end with knurling, to assist with accessing the cell area.

The tailcap has a thick removable spring.  The head has only a brass button, and to be honest, looks like either a frown or smiley face, depending on how you see it.  There is no magnet in the tail.

The threads are well lubed, square-cut, and anodized.  Thus it’s possible to lock the light out with just a very small twist of the tailcap.

Even though this bezel looks removable, it’s at best, difficult to remove.  I didn’t use any tools, but I wasn’t able to just twist it off.  (Other users have done this successfully.)

Inside the cell tube is a little sticker indicating cell orientation.  The head goes in first, as seen in the photo to the right.

Size and Comps

Officially the dimensions are: 64.7 mm long, 23.4mm in diameter, and the weight is 34g.

Sorry for the out-of-focus shot, but here’s the H40 with my force patina ReyLight Brass Pineapple.

Here’s the test light with the venerable Convoy S2+.  Mine’s a custom “baked” edition Nichia 219b triple.  A very nice 18650 light.

Retention and Carry

This light has essentially only one carry mode, and that’s with the headlamp.  The light slips into two silicone loops and fits very snugly.  It’s possible to rotate the light inside this housing.

The light can be oriented with the button on top or bottom.

The headband has a silicone grip section all the way around the inside of the band and stays in place very nicely.  Also worth mentioning is that the silicone part that contacts the forehead is quite comfortable.

I’d love for there to be a magnet in the tailcap of this light.  I do believe that’s a bit of an omission, but I also get it – this is a very dedicated headlamp.

Power and Runtime

The H40 is capable to run from many AA-sized cells.  This includes primary alkalines, NiMH, and 14500.  It’ll even work properly with flat or button top cells, too.

Again, be sure to put the cell into the light positive end first.

Here are a number of runtimes.

Noteworthy about every test I ran is that the light does have LVP, and that includes for Li-ion and NiMH independently.  Also when the cell voltage gets low, the light will flicker on and off to warn the user!

Turbo output with a NiMH cell isn’t quite like the Turbo of a Li-ion.  It’s a much more subdued output, and fortunately the H40 is able to maintain that for quite some time.

High is marginally lower, but also very stable.

User Interface and Operation

There’s just one button on the H40.  It’s a big orange square e-switch and is in the center of the body.  It can be on the top or bottom when the light is in the headband, per your preference.  To be perfectly honest, the switch is probably my single least favorite thing about this great little light.  It’s quite mashy.  Double-clicking for turbo is a bit difficult to do reliably.  The switch works right, mind you, it’s just the actuation point is a bit under so much mashing that it’s … unusual.

Here’s a UI table!

State Action Result
Off Hold Ultra-Low
Off Click On (Mode memory, except Ultra-Low and Turbo)
On Click Off
Any (Non Turbo) Double Click Turbo
Turbo Double Click Previous mode
Any Triple Click SOS
On Hold Ramp up to High (signified by three flashes) then ramp down to Low (signified by two flashes)
Off Hold >3s Lock (signified by 3 flashes)
Locked Hold >3s Unlock to On

Modes and Currents

Mode Mode Claimed Output (lm) Claimed Runtime Measured Lumens Tailcap Amps
Turbo (14500) 600/220 1m/40m 602 1.98
High (14500) 150 65m 136 0.32
Low (14500) 20 7h 20 0.01
Ultra-Low (14500) 5 17h ~ ~
Turbo (NiMH) 180 80m 165 0.93
High (NiMH) 150 85m 114 0.69
Low (NiMH) 20 16h 15 0.02
Ultra-Low (NiMH) 5 43h ~ 0.02

LED and Beam

The light I have is the Luminus SST-20 4000K CRI 95+ option.  The other is a Cree XP-L HD.  The Cree has much more output (over 1000 lumens on Turbo) but the Luminus boasts >95 CRI.  High CRI and headlamp seem to go together extremely well.

The reflector is small, of course.  It has an orange peel texture.  The small size of the emitter coupled with this reflector gives a surprisingly tight hotspot, but there’s a reasonable spill, too.  This light will likely be good for hiking, and on-trail activities.


14500 (Li-Ion)

Tint vs BLF-348 ( 219b version) (affiliate link)

I compare everything to the 219b BLF-348 because it’s inexpensive and has the best tint!

Random Comparisons and Competitive Options….

Here’s a link to a relevantly filtered page on  I use that site a lot!  There are some comparable lights.  Most notably, many of the Zebralight headlamps.  As far as I can tell, the H40 is the only option that supports all these cell chemistry options, which makes it truly stand out.


What I like

  • Very high CRI!
  • Warm emitter – 4000K claim, feels warmer
  • Nice tight hotspot, good for hiking
  • Multi-chemistry support

What I don’t like

  • Button is too mashy for my usage
  • No magnet


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10 thoughts on “Acebeam H40 Headlamp Review”

  1. I have bought this as well as the XPL version. While I generally prefer warmer tints, the floodier beam profile of the XPL version makes it much more usable as a headlamp. With the SST version, I have to rotate the light in the headband to go from “walking around use” to “up close use”. With the XPL, I can get away with both tasks without having to adjust the angle of the light. Thank you for this and the other great reviews on your site!

    1. I have both and agree, although I like the warmer sst20 over the cold white cree version, the spill of the cree is much more usable. I am looking at replacing the reflector in the sst20 4000k with a tir optic that gives a it more flood. Just need to find the right size optic.

  2. KdW, the Netherlands

    I’m looking for this kind of single AA driven headlamp for some time now, and at this moment the Acebeam H40 is available at my local store. I am reading some detailed reviews to see if there are any hidden downsides. Seems there are none besides brightness and battery life, inherent to this type of light. For hiking we are using Black Diamond Icons because of the very long battery live ( 4 batteries in a separate housing). For short hikes, walking the dog and well-lit repairs in and around the house the Acebeam H40 is an ideal headlight because of the unlimited rotating angle. Build quality and other specifications are expected to be OK. Thanks for the extensive review, it has helped a lot.

  3. Your reviews are always awesome, thanks for doing what you do! I come here for the run time graphs on different battery specs, but stay for the whole article.

  4. I have one of these in the high CRI version and I agree with those above; the light does have to be adjusted from time to time and that can be a little bit annoying, but not too much. I cut off the strap that goes over the top of the head and haven’t missed it at all.
    Really like this light. Perfect for chores around the house and working on vehicles. The UI is perfect and the firefly mode is just right. Haven’t used it with lithium batteries, but it doesn’t look like that gets me too much over alkaline or NiMh from the outputs and runtimes in your review. I’ll order some 14500s and see what I think.
    Thanks for your reviews. They are awesome.

    1. Great! And yeah it’s possible on many (most?) of these over the top bands to just lop them off. I just…. can’t bring myself to doing that (but for no good reason!).

      Enjoy your H40!

  5. I leave that top strap on my 18650 headlamps because of the weight, but this one is light enough that it’s not needed.

  6. In this flashlight, you can get diffused light by sticking a matte film, after which it becomes your favorite headlamp.

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