Um, the bad news is I only got about 7 seconds out of it on the lightbox at 4147 lumens, 3976 when it died, poof, just went out. So now I get to go back in and see just what happened. lol
Aww crap. 
Yeah, but dang it’s thrilling for a light this size to pass 4000 lumens! :bigsmile:
Light works fine, just won’t sustain the top end.
Just ran it 18 seconds at max level handheld, get’s REALLY hot, really quick! Still working, but shut it down.
It shut down when on the lightbox, headstanding, with all the heat rising into the copper right at the driver. 
I put one of those spongy white thermal pad things on the MOSFET (came off the driver in my Olight Javelot) and just ran it for 45 seconds in hand.
This bad boy gets HOT! But it seems to be working. It’s been pointed out to me that 15A off 4V is in the 60Watt range or somewhat like a good soldering iron.
Ok, so the 2 minute step-down is somewhat long.
Erm… I think it is possible that the PTC at the positive end of the cell overheated?
This is an Efest 35A, not protected. It is one of the new button tops but it has no protection to the best of my knowledge.
The PTC is a physical safety feature, it is not what you refer to as “protection”. AFAIK all cylindrical Li-Ion cells have that (as well as a CID I think).
Wow, learn something new every day! (I could have already known that, and forgotten it, and learned it, and forgotten it again)
Now I need to do some research, so I’ll be armed with more stuff to forget. Vicious circle, is it not?
One way figure out whether it’s the PTC is to remote-mount the battery. I know that this flashlight does not make it easy, but it’s probably possible with a sliding clamp to hold the cell, a nice jumper cable clamp for the GND/Bat- connection, and some copper rod or whatever for the BAT+ connection.
Or you could just solder some big hookup wire directly to the light engine.
I’m assuming that if it is the PTC then the problem is the heat from the emitters, not the cell self-heating or anything.
The PTC is a thermal switch to help prevent overheating of the cell causing pressure build-up. From what I’ve been able to find online, if the PTC is triggered the cell will most likely be useless. This cell is working fine, recharging fine, working some more. So it really is doubtful that it’s the PTC causing issue here. (Positive Thermal Coefficient) This is the primary information I found. And just now, looking to double check what I was writing, I found this information that contradicts the previous articles (4 different sources)
“Problem
Most commercial, cylindrical lithium-ion cell design are
equipped with a positive thermal coefficient (PTC)
current limiting switch to provide hazard protection
against short circuits external to the cell. This device,
shown in Figure 1, is thin annulus consisting of a
specially irradiated polyethylene laminated with a metal
on both sides [1]. When exposed to an overcurrent
situation, this normally conductive polymer heats up and
changes phases to become several orders of magnitude
more resistive. Once the short is removed, the PTC cools
down and returns to its electrically conductive state. This
device has been a very effective method of providing
reliable short circuit protection in low voltage battery
assemblies. ”
This would explain why, after several seconds, the firmware caused a flash indicating power had been applied, even though I had not taken the light apart or opened it. The switch in the cell reset and power was again available.
So, is 15A+ the top end for the Efest 35A Purple cell? Leave it to me to have found that, huh?
Now I will test the Sony VT C5. :bigsmile:
IMO the issue is that you are subjecting the cell to a very high temperature (although a 15A drain at the same time probably doesn’t help ;)). HKJ successfully tested the Efest ‘35A’ cells at 30A, with strong results at 20A.
The Sony C5, fresh off the charger, didn’t quite allow 14A (13.61-13.91) and showed 3784 lumens at the highest, dropping down to 3450 by the time it was too hot for me to hold my thumb opposing the switch. (54 seconds, as per the video I took while doing this.) I should also point out that I was taking a tail amperage reading with a 14” long 12Ga wire through the clamp meter while the light was in the light box. So the lumens output was lower than if the light had been assembled.
This light with it’s chunk of copper under the quad only dropped 340 lumens in 54 seconds at extreme power levels, I’d say that’s not bad at all!
Point here being that your A17DD-S08 driver is a very capable little single sided slimline device!
Hahahahaha, tell your hand thanks for taking one for the team! https://www.youtube.com/watch?v=qPr-xsQvhgw
The meter is set at X10 (so 10970), the number shown is then multiplied by .345 to get Lumens. This is the multiplier for my lightbox.
Stock clicky DBCstm? ALOT of amps to be running thru a stock switch man
Still awesome as hell bro…all them amps! WOOO!
3000 lumen sleeper…guy is all, look at my light, and you MELT his with a click of the switch
It’s an e-switch with a ramping firmware and a sleep mode. Uses very little (some 40uA) current when not in use. A long press bypasses memory for the lowest position and hold, have to release to start ramping up from there. A double press goes straight to the max level. Single press from any position when on turns it off. Release the ramping and start again within a second and it reverses, otherwise it continues in the same direction if pressed again after one second. 64 steps, top to bottom in 2 seconds, or vice verse.
I find this very handy with the big draw lights, the most options to get the optimal light for the situation or conserve the cell or both.
Under the copper plate that holds the spring in the tailcap is a very strong magnet that holds the light even with this big chunk of Cu in the head. So I can also stop a pacemaker with it.
And it does over 4000 with an Efest 35A, 4147 to be exact.
Holy hot stuff Batman, that thing is a portable reflow oven. Glad you found a use for the copper. Let me know if you see anything else in my builds(rare as they are) that you might use.
Trying to follow the logic on how the top of that cell heated up so fast, I think I might be on to something.
I’ve got a spring on the driver, with a 22 Ga wire inside to carry current, right? So this ends up making a point of contact at the cell that is on the very small side. Okay for 6A, but with 15A… maybe not so much! With that much current flowing through a small space what does it do physically to the wire and spring? Heats em up! Immediately!
So I’m going to put a 5/16” diameter brass post on the driver this morning. Far more current carrying capacity and a major contact surface improvement, giving full contact to the top of the cell. That should solve the PTC shut down issue. I’ve already put a solid copper plate at the negative end, with a beefy spring and also wire bypassed…I’ll put a copper top on that spring for a larger flat surface as well. 
The Sony C5 is a flat top, it ran 54 seconds on the light box without shutting down. The button top Efest shut down within 10 seconds. Smaller top plate, smaller contact surface. (granted, the spring with wire soldered in still gives a small surface contact either way) Could simply be that the Sony has higher quality components.
Does that sound right?
Thanks Scott, that copper sheet has been really coming in handy! The really thick stuff not as much as the thinner, scissor cut capable sheet. But I’ve used the thicker stuff as well, albeit with some more work getting the piece desired.
Edit: I might even see higher current with the blockages addressed! :bigsmile:
It’s hard to say for certain, and I already mentioned some of this, but here goes:
- HKJ managed to get full 30A discharges out of the ones he tested.
- The PTC responds directly to temperature, not current.
- I think it’s a temp issue, not a current issue.
- The PTC on the Efest may simply be using different materials which change more aggressively with high temperatures.
- I think a battery spacer which blocks the flow of heat from the pill to the battery is what you need. Maybe stainless or maybe delrin/whatever with a 12AWG solid copper wire hammered into the middle.
- If problems persist then maybe your Efest batteries are mildly damaged? Although I thought a PTC was supposed to be tough, repeatable, and difficult to damage by it’s nature.