Can BLF A6 A17DD-L be burned by too high current?

PML · 2019-05-05T00:02:20.000Z

Trying to mod my new C8 host with these FETs. Used awg18 wires which was a little pain with integrated pill. Spring bypass done on switch and driver also with awg18. Checked twice or even more for any shortings. Flashlight worked quite well for about 3 minutes with XPL and VTC5 inside then it started to smoke a little from the driver. Again dismounted everything, checked for shortings and I noticed FET module has burned. Changed everything, new wires, second driver and same situation! So as the title says. Can BLF A6 A17DD-L be burned by too high current? It is first time I meet this problem and do not want to sacrifice third driver :person_facepalming:

moderator007 · 2019-05-05T02:26:16.000Z

With a single cell I wouldn’t think so, I have a couple of triple lights using this driver pulling 17 amps from the cell and I have had no problems besides the light becoming really hot fast. It could be the reflector causing the short. That’s a direct short and with a direct drive driver it flows all the current the battery can give. Try with out installing the reflector. Did you notice any burnt spot on the reflector?

madness · 2019-05-05T06:29:07.000Z

I’m using this driver in my Convoy C8 with a Samsung 30Q cell. No problems whatsoever.

SIGShooter · 2019-05-05T06:39:39.000Z

I also have the same driver in a Convoy C8, M1, and several S2’s and haven’t had any problems with using 30Q’s.

everydaysurvivalgear · 2019-05-05T06:54:29.000Z

Yes and no.
Its not a common fault but you could have a FET with not enough solder on it so its overheating. My last couple of BLF drivers have been a bit dodgy and i reflowed the MCU and FET on two of them.

Check the negative wire on the driver because that sits real close to the FET and fairly close to the ground ring could be a short there? 18AWG wire is huge for these 17mm boards.

wle · 2019-05-06T10:58:28.000Z

maybe you have a solder bridge around the FET or elsewhere?

wle

PML · 2019-05-06T21:29:49.000Z

Thanks everybody for replies. I have checked it more than twice, solder joints were straight and clean. In the second driver I was even proud of myself that I managed to do such clean joints with awg18. In both drivers the FET got a small bump in the middle and smoked. Also checked, that maybe when I stripped the wire, some small piece fell on the board and made a short but found nothing. Battery was at 3,6V so knowing quite high forward voltage of XPL the current had to be relatively low.

moderator007:

Try with out installing the reflector. Did you notice any burnt spot on the reflector?

It happened without reflector.

everydaysurvivalgear:

Check the negative wire on the driver because that sits real close to the FET and fairly close to the ground ring could be a short there?

Checked more than twice. But as far as I know it wouldn’t be a problem if a negative wire was touching the FET ground or outer ring? Or am I wrong? Nevertheless there was no contact of negative wire with anything else.

Ok, at the moment I conclude that it was a fault of short-circuit somewhere. Now waiting for smaller wires and will try again.

djozz · 2019-05-06T21:37:44.000Z

A another possibility is that the led is bypassed one way or another (solder joints touching the reflector?

PML · 2019-05-06T23:24:28.000Z

Tested without reflector too. It hasn’t burned right away. Just after 2 or 3 minutes while playing with modes. LED is still ok surprisingly.

moderator007 · 2019-05-06T23:42:41.000Z

With a single XPL I would guess you should be pulling around 5 amps or less from the battery. If you try it again, use a DMM to measure your current draw. If its above 5 amps you got a short somewhere.

madness · 2019-05-07T07:39:00.000Z

I’m getting 4.3 amps on maximum using this driver to power a XP-L HI with a Samsung 30Q battery

everydaysurvivalgear · 2019-05-07T08:24:49.000Z

Negative should not touch the outer ring (ground) if it did your light would not change modes? Although both are ground you don’t want the negative output on the driver output to be touching the ground ring. If it is touching there, that is the issue. That is basically the same as running the LED straight from the battery with no driver.

Any short would most likely fry the driver or you not be able to change modes.

Lexel · 2019-05-07T08:32:37.000Z

the MOSFET is not the best like modders use here
China uses some strange FETs maybe new batch is worse than usual one,
like 20mOhms cause serious heat on PCB which it can not sustain

especially with driver not mopunted to the light it can overheat fast

PML · 2019-05-08T02:30:14.000Z

Ok, one spare driver was lying around so I could not wait and did some soldering at 2am. This time with success and with 2 founds.

FETs on both failed drivers are not touching pcb. There is a very tiny gap which is not present on the third driver. Although it could happen after the FETs burned, bumped and created a gap. Maybe.

LINK
LINK

2. I checked with dmm and found that Convoy C8 driver ring that holds driver on place was not making a contact with driver’s outer ring so there was no ground connection driver-host. Or the connection was so weak that my dmm not detect it. Putting some tin around the driver ring solved that problem. Maybe weak connection was causing high resistance and heating the driver’s pcb?

LINK

After third attempt flashlight has been working flawlessly for about half an hour. Tested each mode.

Photos disappeared so I have added links to google drive.

I want to add that XPL W2 1B after partial dedoming, slicing and bathing in degreaser, but with a thin layer of silicone left, is producing very pleasant neutral tint without any green shifts.

moderator007 · 2019-05-08T03:00:04.000Z

Glad you got it working PML.