Lumintop BLF GT94 Review – Totally Nuts

Contents

The Boring Stuff

Reddit user u/calmlikea3omb (infamous for throwing a Zebralight in a fire) lent me this light for review. Here is the official product page. Below are the official specs. This light isn’t available anymore and it’s been replaced by GT94X, which is basically the same thing but with fewer, larger batteries.

What comes in the box?

I don’t know. This light was lent to me without a box or any accessories.

Design & Construction

Holy cow, this thing is overbuilt. However big and beefy you think this light is, double it.

Size & Measurements

From left to right:
Convoy L7
Lumintop GT94
Noctigon K1

MeasurementMeasured (mm)
Bezel Diameter134.2
Length317
Switch Diameter18.9
Body Tube Diameter (internal) 46.3
Body Tube Diameter (maximum)56.2
Body Tube Diameter (mode)56.2
Body Tube Length162
Tailcap Diameter62.0
Tailcap Length29.4
Handle Diameter30.2

Weight with eight Sony VTC5A batteries: 3.28kg / 7lbs 4oz

User Interface

GT94 uses the NarsilM 1.3 firmware, and it’s a mixed bag. Basic operation is just like most e-switch UI’s. Single click on/off, double click for turbo, hold from on to change brightness, hold from off for moonlight. That’s just in the “ramping” UI though. There’s also a “mode set UI” which I highly dislike.

In the “mode set UI” you click x number of times to cycle up through the modes and it always starts on the lowest. If you stay on a mode for more than a second or so, the next click will turn the light OFF, not go up another mode. Worst of all, a hold goes to Turbo! I had to use the mode set UI for testing, and several times I accidentally Turbo’d all 20,000 lumens instead of going to moonlight like I planned.

If you’re interested in advanced settings (which you should be, to disable thermal regulation), check out the official NarsilM1.3 BLF thread which is full of info, including a link to a manual.

Modes, Brightness, Throw, & Tint

Disclaimer: Unfortunately, this behemoth with a Texas Ace driver will not fit in my Texas Ace lumen tube, so I’m going to assume the advertised Turbo brightness of 20,000 lumens is true and calculate everything else relative to that. A candela measurement was taken at 10 meters with an Opple Light Master III on the highest brightness, and other candela figures were calculated relative to that. CCT & DUV data was taken for each mode from a few feet away at the center of the hotspot with the Opple Light Master and Waveform DUV Calculator. Runtime tests were performed with the Ceilingbounce app on my smartphone. All of these tests were performed with fully charged batteries unless otherwise specified. I cannot measure moonlight directly, so moonlight readings are calculated based on the brightness relative to the next-lowest mode. None of this is professional equipment, so take all of these measurements with a grain of salt.

Level Lumens (@ Turn-On, Estimated)Candela (@ Turn-On)Throw (meters)
Full2000016000002530
4088607088001684
1034827840334
5403200113
2324030

Why those modes? It’s hard to get repeatable testing from a smooth ramping light, so I put GT94 in the “Mode Set” UI for much of my testing. I chose mode set 5 because it best matches the “moon-low-med-high-turbo” mode sequence I prefer on most of my lights. “Full” is FET Turbo. “10” is the highest regulated level. “40” appears to be PWM limited FET drive.

Mode Spacing: Mode spacing can be customized based on the mode set. Mode set 5 which I have chosen has a huge brightness jump between mode “10” and mode “40”. Alternatively, the smooth ramp is fairly smooth and is a consistent speed.

How does it compare to the official specs? I can’t measure lumens on this beast, but the candela is right on the money.

Runtime

Please disregard the hump in the “FULL” line below. I had to adjust a fan during the test and it changed the readings slightly. In reality, there is no brightness increase at 6 minutes.

Performance: Thermal regulation was disabled and the highest two modes were run cooled by a fan. Turbo performance is blistering and it will get too hot to hold after a couple of minutes if you’re not actively cooling it. Turbo (“FULL”) only lasts about 15 minutes before low voltage stepdowns kick in. High (“40”) lasts considerably longer, about 40 minutes. Medium (“10”) lasted twenty four hours.

LVP: Narsil does have LVP built in, but I never let the light run long enough for it to kick in. Additionally, there are several low voltage stepdowns to warn you the batteries are getting low.

Driver & Regulation

GT94 uses a “Texas Avenger” driver, developed by BLF member Texas Ace. I use one of his lumen tubes for my lumen testing. This is a FET+7135 driver, with the FET channel handling higher modes and the 7135 channel handling lower modes. I’m not certain how many 7135’s are present, but my guess is it’s just one, which is pretty disapointing.

The lower modes (“10” and lower) that are driven by the 7135 chip(s) appear to be constant current driven because they are quite green tinted. As soon as you exit 7135 drive and enter PWM limited FET drive, the tint gets way cleaner. Unfortunately, you can audibly hear the PWM anywhere between “10” and full FET Turbo.

Regulation: No need for separate regulation testing here since I was able to disable thermal regulation completely. See the runtime graphs instead to see how well the light can sustain its brightness at various battery levels. Basically, it’s poorly regulated at higher FET driven levels, and well regulated at lower 7135 driven levels. Unfortunately, the highest regulated level is only a few hundred lumens.

Note: All regulation measurements are taken at turn-on so they do not reflect any thermal or low voltage stepdowns that may occur. A value of 0 indicates low voltage shutoff immediately upon activation.

Thermal regulation: Is present by default and it sucks. I did several cooled runtime tests with a desk fan blowing directly across the fins at full speed. Every single time, thermal regulation kicked in and dropped output down to a few hundred lumens. The light would then cool off, but the brightness never stepped back up. That’s nonsense. You should completely disable thermal regulation immediately upon receiving this light.

Emitter & Beam

The 94 in GT94 refers to the four Luminus SBT90.2 LED’s. SBT90.2 is just about the biggest and baddest LED on the market at the time of writing, producing up to a whopping 5000 lumens while also managing to throw pretty well too. It’s a 3V LED, but GT94 uses a 4S battery configuration and a FET driver, so the four LED’s must be wired in series.

The beam is fairly clean for a quad reflector like this. There aren’t any weird artifacts aside from huge flower petals at the edges of the spill. Those are a result of the quad reflector. It’s pretty green at low levels but the tint cleans up a lot as soon as you exit the 7135-chip regulated levels and enter the FET driven levels.

GT94

In the beamshots above, the trees where I’m aiming the hotspot are 175M away. In the beamshots below, the park bench where I’m aiming the hotspot is 42M away.

GT94

GT94 blows my biggest throwers (Noctigon K1 SBT & Convoy L7) out of the water. It can induce giggles in anyone who holds it. It’s truly awesome. Check out these drone shots courtesy of u/jonfromm!

GT94

Switch

There’s an electronic side switch located on the head. It’s covered by a black rubber boot that allows a bit of green backlighting to show through. It’s a fine switch, but I really wish it were on the end of the carrying handle.

Carry & Ergonomics

This thing is a beast and it’s too much to hold in one hand by the body tube. Thankfully, there’s a nice, ergonomic carry handle included and it works great. I have one, large complaint with the handle: the switch isn’t on it. It’s awkward and cumbersome to be holding the light by the handle in one hand and have to reach around to the other side with your opposite hand and press the switch. The switch should be on the end of the handle.

If you’re not into the carry handle, it can be removed. Underneath is a tripod mount and there are two shoulder strap mounts on the head and tail.

Batteries & Charging

GT94 uses eight, unprotected, button-top, 18650 batteries. For best performance, use cells with a continuous draw rating of at least 10 amps. I’m using Sony VTC5A button tops. To hold all those batteries, a carrier is included. The owner of this light had some trouble with his carrier so he uses original BLF GT battery carriers instead and they work well, provided the center contacts are screwed on all the way.

No charging solution is included. You’ll probably want to get an 8-Bay charger to charge all these cells at once.

Competition

Here are some lights in the same class and how they compare.

Lumintop GT94X: basically the same light but with 4×21700’s by default instead of 8×18650’s, optional 8×21700 extender

Wuben A1: better handle with integrated wireless remote, battery pack consisting of 8 21700 cells, powerbank function, integrated (not USB) charging, very very expensive

This section is not comprehensive. If I didn’t include a particular light here, it doesn’t mean it’s bad or doesn’t deserve to be here. I simply cannot list every possible competitor.

Conclusion

This light is monstrous and incredible. I cannot think of a reason anyone needs this, but that is no excuse not to have one. This is just about the pinnacle of insane hobbyist flashlights and I love it.

Thanks to u/calmlikea3omb for lending me this light for review!

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