1-2* Lithium 2-Group 3/5-Mode 2.8A LED Flashlight Driver (LD-29)

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Driver is from Fasttech.com

Official specifications:

Perfect for Cree XM-L series LEDs -- especially with T6 and U2
Dual PCB layout, 10mm total height
Designed for Cree XM-L LED emitters
Also works with four MC-E's and four SST-P7's connected in parallel
2800mA maximum current output
Low voltage warning battery protection mode triggered when voltage drops below 3V (in 1-lithium configuration) or 5.8V (in 2-lithium configuration): automatically switches to the lowest output setting, and blinks periodically
Modes:
Group 1: Lo (5%) > Mid (50%) > Hi (100%)
Group 2: Lo (5%) > Mid (50%) > Hi (100%) > Strobe > SOS

To toggle mode group:
Switch to Lo (5%) mode and count exactly 5 seconds. As soon as the flashlight blinks, half press (or quickly toggle power) to go into the other mode group.



Measurements

Tested with: Cree XM-L2
The driver uses buck mode
Driver diameter 18.6mm + 21mm
Driver height 8mm
The driver has memory, the actual mode is stored when the light is off for a short time.
A off/on will select next mode, the off has to be rather long, not to select next mode.
Mode set 1: High, medium, low, Strobe, SOS
Mode set 2: High, medium, low
The driver can be used with 1 or 2 LiIon batteries in series.
Strobe is 15Hz with 43% duty cycle
Threshold between 1 and 2 cell is between 4.5 and 5 volt



High

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V

The drivers has very good regulation and good efficiency. It turns power down at 6.7 volt and battery warning comes on at 6 volt.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4VDriver

There is a maximum of 1.5 watt lost in the driver, while delivering 9 watt to the led.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4VLed

High%207.2V

No noise in the light.

LowVoltage%205.9V

The low voltage warning is a slow flashing.


1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V

With one cell the stabilization only works down to 3.7 volt, that means no stabilization for half of the runtime on a single LiIon cell.
The driver has a low voltage warning at 3 volt.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5VDriver
1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5VLed

High%203.6V
LowVoltage%202.8V



Medium

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V%20medium

Medium has the same good stabilization and does not step down, it goes directly to low battery warning at 6 volt.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V%20mediumDriver
1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V%20mediumLed

The led power is down to 2 watt.

Medium%207.2V

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V%20medium

With lower led power, the driver can sustain the medium level down to about 3.2 volt and it has very good efficiency.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V%20mediumDriver
1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V%20mediumLed

Medium%203.6V



Low

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V%20low

The regulation is also good on low, but the efficiency is slightly down.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V%20lowDriver
1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%208.4V%20lowLed

Low%207.2V

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V%20low

With a single cell the driver works down to about 3 volt with full stabilization, before it goes into low voltage warning.

1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V%20lowDriver
1-2%20Lithium%202-Group%203-5-Mode%202.8A%20LED%20(LD-29)%20HL%204.5V%20lowLed

Low%203.6V



Strobe

Strobe%207.2V
Strobe%203.6V

Strobe is 15Hz with 43% duty cycle, the driver cannot reach full brightness with a single cell


SOS
SOS%207.2V
SOS%203.6V


Conclusion

The driver is a very good stabilization (Except on high with 1 cell) and good efficiency. The mode change could be better.


Notes

I have tested a slightly different LD29 driver before, with nearly the same result.

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