Fasttech SKU 1127402 boost driver behaviour

Flashlight Modding and DIY Parts
1

https://www.fasttech.com/products/1127402


I ordered two of these boost drivers and checked the current draws in various battery configurations.

Using 1 NiMH cell fresh off the charger it draws 2 amps. With a more depleted battery the current draw goes down to 1.7 amps, and it draws 1.0 amps from an almost empty cell.

So I thought it was an unregulated driver, drawing more current with higher voltage.

But if I use 2 fresh NiMH cells, the current draw is also 2 amps, just as with one fully charged cell. So it seems to be regulated to some extent.

The fasttech product page states the following:


Booster driver mode when input voltage is 1.5V or less
Linear regular (constant current) mode when voltage is between 1.8V and 3.6V
Rated at 500mA current output @ 1.5V input
Rated at 800mA current output @ 3.6V input


I don't understand the part about the boost driver mode. To my understanding, the driver has to be always in boost mode if the input voltage is under the Vf of the LED.

What do you think?



Comparing these values to this popular DX driver, it is obvious that the DX driver is regulated, trying to supply constant current to the LED:

http://dx.com/p/1-5v-4-2v-3w-cree-circuit-board-for-flashlights-16-7mm-5-6mm-25505

1xNiMH: 1.8A
2xNiMH: 1.3A
2xLithium AA: 1.1A

I think I still prefer the DX driver, but the FT one gives more juice at higher Voltages.

Edit: fixed typos

2

FWIW, I just tested both drivers with 3NiMH cells and they both draw about 1A. The FT driver a little more, the DX driver a little less.

So if I see that right, both drivers are regulated, but the FT driver drops out of regulation at a higher voltage than the DX driver.

3

I'm starting to feel like a lunatic talking to myself, but maybe somebody will find this useful sometime.

I used another one of the FT drivers, this time in a P60 dropin with an XP-G2 and it behaves totally different. Mind that I used the first one with an XR-E, which has higher Vf, so I somehow expected different results, but not in this dimension.

Anyway, here are the tailcap currents of the FT driver with XP-G2:

1x Eneloop AA: 1.8 A (~2.3 W)
2x Eneloop AA: 0.58 A (~1.5 W)
2x Energizer Lithium AA: 0.6 A (~2.0 W)
3x Eneloop AA: 1.5 A (>5 W)

I don't know what exactly happens here, maybe one of my drivers is defective. But then again, they both work, they just behave differently. To solve this mystery, someone with better tools and more knowledge about drivers would have to test a couple of these.

Myself, I think I still prefer the DX driver, it just behaves more predictable. The FT driver however has better wires and an overall nicer build quality (judging from nothing but the look and feel of everything). If you just want to have light and don't care about numbers, either of them are fine.

Thanks for reading :bigsmile:

4

I ordered the AA driver with 402 on the end, too.
It was kind of weird, I got not so happy with it.
End result was a direct driven sipik with a dedomed xpg2…

The 1A driver from fasttech works okay for me and I have ordered the 1A nanjg from intoutdoor for my next use.

To give you a hint how these drivers often work, if you use a higher input voltage than some of the driver switch to a direct drive which puts a lot of current through them. sk68 stock driver for example if used with a liion

5

Well I ordered 3 for MiniMag mods.

Guess I’ll see how I like them with 2 AA batteries.

6

I just ordered a couple of these https://www.fasttech.com/products/1127407

The pictures don't look much like the OP's model but the descriptions regarding outputs are almost identical. I wanted a three mode but this 5-mode was as close as I could find.

Steve, I really couldn't make much sense of the specs either. I plan to use mine to drive an XM-L in a Balder SE-1 which seems to have fried its driver.

You don't have a way of measuring emitter current rather than just tailcap I suppose?

7

Thanks for your feedback guys.

Gadabout, theoretically I could measure emitter current with a DMM. I already thought about desoldering one of the LED wires, but I imagined myself balancing between blinding myself and shorting the driver... I guess I would would have to build some kind of testing setup, and I'm so darn lazy

I also ordered of these drivers, curious how that one is. According to the specs it should give some juice.

8

Thanks for posting measurements, Chief.

I’m guessing the driver is designed to only draw about 2A max. The designers probably realize that if it drew much more than 2A efficiency would go down and the components’ longetivity would suffer due to excessive heat.

9

Thanks for sharing!
Emitter vs tailcap measurements would make it considerably more interesting though.

10

Steve, I understand completely. It is quite a fiddly test to perform.

I saw the driver you linked to at Fasttech. I have read about it previously and followed your discussion thread on the product page but the answers and numbers given there make no more sense than the description. There is no way that this driver should be pulling 3.9A from two NiMH to output 1A to the emitter. We are still waiting for them to test it.

As much as I like Fasttech some of their product descriptions and lack of proper information is extremely frustrating. It's like the potential buyers have to keep editing their specs for them. (Still, they are streets ahead of most of the cheap Chinese vendors I guess.)

Anyway, I'm after a 3-mode driver rather than a single mode.