Niwalker BK-FA02S --WARNING: a direct short waiting to happen in the batt carrier

You mean you shorted it? My case is different, as explained above.

Interesting:
Sounds like what I had happen to a Acebeam a few years back, with a battery carrier issue. They had to redesign it to Properly handle the amperage draw. So, that makes me think you got a carrier that has a problem. Maybe a bad connection or cold solder joint? I don’t have one of those lights, so not sure how the carrier is designed. Have others with this light had this problem before?
It also sounds like what happened to a carrier I made for a OL custom maglite. It melted too, and the cells burned my hand. All because the Amperage draw was too high for my design.

Good luck.

I just noticed that the voltage of the BK-FA09 is 11v to 16.8v, while the BK-FA02s/BK-FA01s are 4.9v to 8.4v.

Assuming batt carriers were mixed-up, will it have a bearing in my case?

yes. I shorted the light out by accident. the spring pretty much welded itself into a shorter length.

my first though is when you put the wrong battery carrier in the light two cells were in series but facing with both plus or minus poles together
like —- instead of+±

Yup, that is my thought too. The carriers will almost certainly be wired differently so by putting the carrier in you would have basically shorted it out with the carrier. maybe you can check the carrier connectors on the light to the carrier connectors on the carrier. Might be more obvious that way.

I’m sure I inserted the cells in its correct polarity, and though the manual says the batt carrier can be inserted either way, this carrier can only be inserted in one way only as there is a clicky switch on one end of the carrier and it goes to the end near of the tailcap with a rubber clicky cover.

Sounds like you’ve got the wrong carrier if you can only put it in one way round as the website clearly states “Battery holder can be loaded into searchlight either way”

EDIT… .this website: Thrower | Markus Speckmeier IT-Consulting Blog

Gute Sache: Beide Vostro-Modelle haben nun einen Clicky am Lampenende, der zum Ein- und Ausschalten und damit auch zur Unterbrechung der Stromversorgung gedacht ist. Damit lassen sich die Lampen “hart” ausschalten und es gibt keinen Kriechstrom mehr.

Good thing: Both Vostro models now have a clicky at the end of the lamp, which is intended to switch on and off and thus also to interrupt the power supply. This makes the lamps “hard” off and there is no leakage current

Battery carriers suck.

But good luck solving the issue.

if the battery carrier can rotate in the light, it provides 2 poles to the light,
good thing is you have not fried the light with 4s voltage

My thought is one battery was in wrong direction, so you get an effective voltage of 2s
inserting the battery carrier to the light and closing the circuit over a FET or converter
now current starts to flow through all 4 batteries, but one is in different dierection

the outcome is that one cell will work against the other 3 cells as it doesnt like to be reverse charged

but as you said the carrier can be separated by the switch in the tailcap you arenot having a 4s carrier
instead you have a 2s-2s carrier
positive light - switch- negative light 16.8V
positive light 2+2- switch 2+2 negative light 8.4V
you end up with 16.8V and most likely burn the driver down turning on the light
positive light +- switch -+ negative light 8.4V but wont allow an effective current flow, and all current will heat up one cell
while a high reverse current will flow through the ++ cells heating em up

(borrowed images)
Heres the BK-FA02s carrier… is this what yours looks like? It looks like a 2P-2S arrangement for 8.4V. Not sure what would happen if you connected your light to a 16.8V (4S) carrier. But thats 2x the voltage. I would think most definitely that would have a significant bearing. Flashlight circuits have some degree of safety factor built into them to accommodate for production variations… but double the max Vin would be pretty unlikely.

If your carrier is the old type one , without the switch means that can be put in , disregard witch side going in (double sided) !

BUT... in a review done here , on BLF, I do not remmember by who , has been noticed that inside the body that hold the carrier is a spring that COULD short the center (+) of the carrier with the heads of the screws (-) . I've noticed that on mine , so , using a long nose plier I insulated the spring up to the first turn with silicone insulation (was a 18 size or so...). Maybe is your case , I'm just saying...

Good luck !

Yes, the carrier that arrived with the light looks like that.

Warning: A direct short waiting to happen in the battery-carrier of this light…see the op.

the same thing happened to me in the original model. i thought i put the batteries in wrong. when the light wouldn’t come on i opened it up and the batteries fell out because the springs shrunk. i put in protected button tops because flattops wouldn’t fit any more. used the light a few minutes and it was fine but the next time i turned it on it wouldn’t work. i inspected the battery carrier and found a trace on the battery carrier’s circuit board melted. i believed it was caused by the wide anode on the flat top making contact with the trace. of course i didn’t figure that out until i paid $30 for the repair

I will be contacting Niwalker about this, for IMO, this design is not only faulty, but extremely dangerous. :person_facepalming:

In the meantime, I wonder what safe remedy can be done to the battery carrier? (Please read the op)

I hope some of our more experienced members here have a thing or two on this matter.

Thanks in advance.

You reminded me BTU shocker modding days.

Hmmmm, these are my thoughts on the subject.

  • If there are any of those raised rectangular solder blobs left, shrink them down a bit. Either re-solder, file, or Dremmel to make them lower.
  • Then insulate anything that could possibly cause a short.

Thanks for taking time to analyze…l have thought about this approach but it still can be a little too risky for 2 reasons:

  1. The positive protrusion in the carrier is just high enough for a flat top to make contact
  2. The original and my replacement springs are quite stiff.

lt will be just practically be a few mm away from another short, but filing the rectangular solder blob then covering it with an insulating material might just raise it nearly as tall as the positive contact, and still be too close for comfort.