Ya. It looks like the same circuit. The only difference there is the the spring needs the negative battery contact instead of possitive. I’m having trouble seeing how they made that happen. None of the charging circuit is in the driver so none of that is a factor. I think your suggestions above should help clarify where the ground is um… being grounded.
I’ll check back in with my findings after dinner…
I think you're messed up on your pin numbering or something, because I can see pin 4's ground connection right there with my own eyeballs.
I’m sorry, I’m having trouble explaining what is happening. Yes pin 4 is connected to the grounding ring, but they are not connected to battery neg so they are not truly grounded. So they are not connected to the same ground as R2. R2 is connected to the battery neg(power supply neg) because there is a via straight up from the spring, which remember, connects to battery neg. So the question is why is why isn’t there a connection from the grounding ring to battery negative. The driver can’t run because there is no connection to pull amps. IDK. I’m trying to ramble so hopefully I can communicate correctly(I know I have a problem with that).
So now… I can get the driver to work if I connect the battery directly to the grounding ring like you suggested. This completed the connection that was not happening through the spring. That’s a good sign and means the driver works. The only thing I can think of is that there is a damaged trace in the driver somewhere
If I were to design this board, I would take a trace from the spring and bring it up under the one of the 7135s to its gnd solder pad. And the only pad that doesn’t have an output trace under it is the one closest to the led+. So that is where I would bring up the ground, but I can’t tell what’s user there and I don’t know what could have happened to it that would completely sever it. Are traces susseptable to this? I’m just guessing on all this. So… It would be odd to let full current travel through one little trace.
Ah ha! I was right. There is another via that goes up from the spring pad to the center leg of the 7135 closest to the led+. I reflowed some solder in there and reflowed the spring back on. And we have light!
Thanks for the help! I was pretty discouraged on this one and this was a lift to my evening. I should know by my age and through the challenges I’ve been through that there’s always an answer around the corner. Notice I didn’t say “just” around the corner as sometimes you turn the corner and the answer is miles away, yet it’s there 
There has to be some vias on the springpad to the other side, if you find this(just unsolder the spring and check were they are you should see were the GND should go…
———
In my eyes judging by the review of the Thorfire bd04 what I think is the same…Review: ThorFire BD04 USB Rechargeable Flashlight
all the charging is implemented in the tailcapbatteryholder thing and the rest is a simple nanjg style driver with adjusted traces for the batteryholder…that would mean that we should be able to fix it because all parts are interchangeable with a standard driver…
Edit glad you could fix it….but I wonder why it failed working?
Thanks Beat you to it:)
Weird. I’m surprised that a single via handles the GND connection. I don’t think that it was a good idea to place that via under a pin either. IMO this could have easily been avoided when they created the layout. Interesting/strange setup overall.
Offhand I couldn’t see why they designed this for a “backwards” battery (they could easily have done it “forwards” with the tray configuration)… but now I think that this was to maintain compatibility with flat-top cells?
Glad you got it fixed.
Hmm. Ya. IDK? Since the via was going straight up to the pin pad and not the bottom pad as I had thought, it may have room for three more vias going to the other 7135s. But I didn’t notice any others under the spring and it would have been very unlikely that they were all unconnected.
Even though there are some questions about the design, I realy do like the light. It charges well. And though the charge cap feels cheep, it makes good contact and is secure when connected. The light itself does not feel cheap in any way. The head slides nicely and gives a good focus just passing up the clear square. Maybe I will try to do my first review/mod thread. We’ll see.
Orsm detective work to all involved. It has been interesting reading.
Thanks LightRider :+1:
You saved me a lot of troubleshooting. I added 4 7135’s, but didn’t solder the center pins, just the back pad. Wouldn’t fire. After looking it over, and probing with my dmm, I realized I wasn’t getting ground. I got to thinking about this thread. Sure enough, I flowed a little solder to the center pin, and it fired right up. Not sure how to test current with this setup, to make sure I’m using all the 7135’s.
Dusty, I did the same to mine and to test current I used a bench supply at work and my clamp meter and fed it power set for a regulated max of 10 amps and found that it really used around 3.4 amps at 3.9 volts.
Glad you figured it out! It’s definitely a design flaw. Fun light though. The optics could be better, but a very usable light for everyday tasks.
I received a few comments about not having to solder the 7135 center pin on my BD04 when I posted a pic of my work in the other thread. Luckily it was my First stack of 7135 and I didn’t know any better. I guess lack of experience was in my favor on that one.
I had only stacked chips on 1 other driver. I soldered all pins. It was almost a futile effort, but I finally got it. I was really surprised this time, with how easily it went. Thought I would save time, NOT