Test/review of Led driver 17mm 3A LiIon Fasttech 4594600

Led driver 17mm 3A LiIon Fasttech 4594600

The last image is from after my test.

Driver is from Fasttech.com

Official specifications

  • Operating Voltage: 3-4.2 -volt

  • Output Current: 3000 mA

  • Flashlight Modes: Lo > Mid > Hi

  • Mode Count: 3

  • Mode Memory: Yes

  • Cable Length: 3 cm

  • Depth: 3.5 mm

  • Height: 17.5 mm

  • Width: 17.2 mm

  • Max. output current: 3A

  • 3-Mode: Low(80mA) > Mid(700mA) > Hi(3000mA)

  • Diameter: 16.8mm

  • Height: 3.4mm

  • Driver has memory.

  • A short off/on selects next mode.

  • Driver uses linear regulation.

  • The modes are 85mA, 0.9A, 3A

  • Double click for strobe.

  • There is battery warning below 3V

Test is with XM-L led


The driver can maintain full output until 3.5V, then the output starts dropping.
Being a linear driver the input and output current is the same.

Power loss in the driver depends on difference between led voltage and input voltage, with a fresh battery it may be around 2 Watt.

With 3A to the led the output power is around 10W

No PWM, only a bit of noise in the signal.
Blue line is voltage across led and yellow line is brightness measured with a photo diode.

M1: 109.1°C, M2: 130.1°C, HS1: 165.6°C
But the driver needs cooling when running in high, this was less than a minute with 4.18V in, i.e. about what a fresh and over charged battery may deliver.

M1: 81.6°C, M2: 103.9°C, HS1: 117.5°C
Dialing the voltage down to 3.88V reduces the heat some, this is again after a minute and a good battery can keep above 3.9V for 10 minutes!

The battery warning signal is fading off/on every 3. second.


At medium the output can be maintained down to about 3V

The power loss in the driver is up to 1 Watt

Power is about 3 Watt

Again the signal is smooth without any pwm.


At low the output can also be maintained down to 3V. When the low volt battery warning is activated the current drain increases.

Not much power loss in the driver at this low current.

The led gets about 0.25 Watt

Without any PWM.


A couple of fast off/on will activate strobe, it is 12Hz with 50% duty cycle

The led current is 3A in 50% of the time when in strobe mode.
The efficiency and current in curve is wrong for this mode.

Just to verify the current I used my current clamp.


This looks like a nice linear driver for 3A leds from a LiIon battery, but it need good cooling on the mosfet transistor when running in high mode.


How do I test a led driver
List of all tested drivers

Thank you for the test.

I like this driver, but I do not like memory: is there a possibility to do the “pencil trick” on one of the capacitors to remove memory and let the driver start in low all the time?

This is LD25 driver, which is “also available from Simon store:

All modes are programmable (except for strobe). Recently it arrived to me and I already checked. Works great.

There is another layout on the movie. I marked the programming (set) pin in red.

Hope it’s useful :slight_smile:

Thanks for the review. HKJ. I’m sure a certain member will be very happy with your results.

Also thanks to Chatika vas Paus for the video, can you also reduce current in each mode?

Reducing current you need to tab the red wire to brass ring and if you hold it will increase current.

ordered this driver 2 weeks ago. cant wait to get my hands on

Thanks, nice to see a driver review :+1:

Thanks. :+1:

Nice indeed. Used a few of these already, now I can understand why I had a hard time trying to measure its output flicker with VISO Flicker Tester.

MOSFET temperature speaking, once the driver is installed in a flashlight it is able to transmit heat to the host, thus its effective temperature should be considerably lower ( :???: ).

Nice to see mode current can be adjusted, but I would certainly thank a more careful explanation besides what's seen in the video.

At last, let me say the driver has two track jumpers on the underside, one of them comes stock closed and the other is open:

In Chatika vas Paus photograph, the closed one is above, the open one below.

In this picture by me closed one is to the right side, open one at the left.

I wonder what do they do.

Cheers ^:)

My driver from Simon arrived with open jumpers.
I asked about this Simon. His answer: it’s useless

Let's see if I understand how current can be set for a given mode. Initial conditions:

  1. Driver has an attached load (emitter).
  2. A way to determine emitter current is set up.
  3. Driver is powered with a voltage source beefy enough to overcome all burdens.
  4. Driver has adequate cooling.
  5. Driver mode to adjust is selected.

Then, when connecting the adjustment wire to ground driver will alternatively increase or decrease current until adjustment wire is ungrounded or some limit is reached. Is this right?

I wonder how low can it go.

Cheers :-)

These look the same just rotated.

A really detailed explanation would be great!
I do not know how far you can reduce the current but i see a sens resistor. And usually playing with it, in or decreases the current. Could be a last resort if the programming is not enough.
I increased the current on my TN31 (K40m driver installed) a long time ago by switching the sense resistor from 100 or 82mOhm original to 50mOhm. And when i turned it on for the first time i was thinking : it’s alive it’s alive. Huge difference!

Hey Barkuti

have you receive your driver yet?

I’m curious to know what is the lowest current it can go.

I have 2 drivers. I think it’s highly depends on used led battery.
1,49mA with Jaxman LG led and Sanyo NCR18650GA
4,6mA with LH351D and Panasonic NCR18650B

thanks Chatika

so the driver can adjust the current for each mode?

5.6mA is true firefly and this is what im looking for :slight_smile:

Little mistake, already edited. Its 4,6mA, not 5,6.
Yes, each mode can be changed. Just select the mode in which you want to change the brightness and taptaptap (I recommend doing single/slowly taps) to reduce the current and hold for increase.

I noticed something strange. I have reduced the current of the lowest mode to about 35mA. After switching from Hi> Lo, Low it ramping from 0. It doesn’t work when turning on at lowest mode.

What does he said? :-D

Err, do you mean that, when switching from high to low, low starts ramping from 0 to your 35mA current setting? How fast?

Cheers :-)

Fast, but it can be seen. Half a second, maybe less. At 60mA, I didnt notice it.

Adjusted low mode to 100 mA and sometimes I see ramping too. Also my driver had strange modes by default: med 1.1A, high 2.2A. However, “set point” works as expected and all modes adjustable.