My apologies if I made it seem as though your suggestion were under fire. That was not my intention, and I imagine ThorFire and the Q8 development team will accommodate numerous cells.
I’m newer to this forum but I have full faith in the BLF team. You guys are rockstars by all accounts.
I would prefer if both springs would be longer and a long range of batteries can be used.
OK I took all the springs off
Then pulled on the small ones and stretched them to a minimum of 9mm
Reflowed them (lol now the tail PCB also has burnmarks from the same gasflames )
All cells fit and it works as before.
Do you need to use batteries longer than 70mm?
For a little perspective, the only battery I know of that’s 70mm+ is Lumintop’s LM34C at 70.7mm.
A maximum of 70mm should yield an ideal leeway. It’s often impossible to decrease battery length (with the majority of skillsets) while adding length is relatively easy.
Gonna be hard to find those long cells
Mabe these: Review Brinyte 18650 cell with build in charger
yes Test of MecArmy 18650 U18-34 3400mAh (Black-red)
These cells with build in charging based on a Panasonic Protected cell should be the longest cells that can be bought now right.
As at least $10 a piece the set would be $40 minimum, the same as a Liitokala Li500 AND 4 good cells
I strongly recommend buying the second set for a nice Liitokala charger is versatile and can be used for more cells where cells with build in charger onlu charge themselves
Reminder of this, please note the wide size options already in place and that a little longer small spring allows even the short 30Q bt to connect to both springs in the double spring setup, no brainer if you ask me.
Are those similar to the Lumintop LM34C at 70.7mm? The LM34C has integrated USB micro charging ports for as little as ~$6.00 USD on BangGood during sales.
But yes, like many others, I will be using 30Q, VTC6, and protected GA.
My longest cells are Protected Imalent 3000mAh 15A with around 69mm. (From my defect Imalent DT35. I wasn’t able to ship it back with the batteries)
I think 70mm is a good maximum point.
But both springs should have contact on short batteries too.
Yes I think all those cells with internal charging were roughly the same
And yes good contact is key 
A question to everyone:
The current prototype on quality 30Q cells puts out 5700 lumen on full batteries, well over what we spec’ed beforehand. Per led that is 1425 lumen, the bare led output I estimate at 1700 lumen. That is at 80% of maximum output of the XP-L V6. For me 80% is always (even in flashoholic perspective) the ideal compromise between output and efficiency (for any led), more power will (simply put) mostly generate heat and just a bit of extra light.
This output is obtained, as it appears now, without the second small springs under the larger spring engaged. For me this tells me that the small spring (whatever it will add) is not really needed for the Q8, and in my opinion because we are at 80%, not even wanted.
In principle we will stick to the extra spring, don’t worry, but I’m just wondering if my opinion is shared by anyone?
Really? In that case l’d forego the smaller spring then from the savings of that, perhaps replace the big springs to a more beefy, or higher quality one.
My opinion:
If there is an extra spring, it should be useful.
It doesn’t make any sense that the smaller inner spring won’t make contact with the battery when the larger spring is pressed, in that case, just leave the smaller inner spring and replace the larger spring by a thicker one.
I agree with Jos, it is best to change the smaller inner spring with a larger one, and keep the current larger spring ‘as is’ so both springs have good contact with the battery, so an individual spring can handle a higher current and reduces the resistance as well.
:+1: I totaly agree. Pushing the LEDs up to 80% right in the sweet spot is perfect (heat production to light output ratio). It protects the LEDs , gives more runtime and it makes the light save to use for almoste everyone. And the ones that want to push it further will definitely bypass the springs anyway
Sorry, haven't had much time as of late, but I plan on doing this mod to be able to accurately measure amps in the round 3 Q8, same as done to the first prototype:
I agree - my vote would be to raise the height/size of the inner spring to at or near the height of the outer, and possibly use a higher outer spring, not much higher though. I don't think they could reliably source better quality springs. Again, the conductance of the spring is dependent on the coating, not the spring steel itself. Thicker steel only means more stiffness. Granted most likely thicker springs will also have thicker coatings.
Sorry - I should have picked up on this and noted it for the round 2 prototypes - they had the same spring setup, though can't be sure the dimensions were matching. I suspected the springs might be a bit short, but with the variety of protected cells I tested of varying lengths, I would be concerned making it more difficult than already is. I suspect even though the short springs are not making top contact and compressing, they are still contacting the outer springs, thus reducing the resistance somewhat. The longest loops of the springs are at the bottom, so where ever the inner spring contacts the outer springs, it increases the flow, reducing resistance. I would not assume just because the top of the inner spring is not making contact, it's having no effect. I believe this explains why we still get pretty high output readings on short cells.
With classic single springs and FET based drivers, it's easy to demonstrate how more compression results in more amps - I've done this dozens of times. It's also true that amps go up initially with bare springs - I've seen this dozens of times, I assume it's heat related. When you bypass the spring, the rise in amps goes away, but of course you get a lot more amps with the bypass in place.
Tom, is it confirmed that the conductance of steel springs is for the greater part caused by the coating? I ask this because steel is a metal and will be conductant (though way worse than copper), and the percentage of any coating in the cross section of spring wire will be very small, I guess in the order of 1% or less? Or is it much more than that?
I repeatedly have bent the top of springs with pliers to open up space for a bypass. In doing so, on the cheaper springs, the coating comes off at times. I've tested the underlying steel for conductivity with a DMM and got no reading. I end up using the spring, but be sure I solder to a coated surface that's closer to the bottom end. I've been searching and searching and thought there was some info on this in an old thread here on BLF but can't find it. Coating thickness and specs on coating materials used is somewhat sketchy to find listed for springs. Gold plating is the best, but hard to find. Hank of course claims this here: http://intl-outdoor.com/gold-plated-springs-for-drivers-and-switches-20pcs-p-866.html, but he is one of the rare China sources I believe because I know he verifies this stuff personally and is a stickler for details and quality, plus a rare supplier of true quality beryllium copper springs, as you tested.
Ohh - electricity will seek the path of least resistance, so that's why it uses the coating of the springs, not the spring steel itself. Flashlight springs will always use a favorable conductive material for the coating layer, plus solderable of course.
Edit - also somewhere I saw tech data on how electricity travels thru solid copper wires, and I thought it was pointed out it mostly flows on the outer surface - there was some debate about hollow wires being as good as solid core because of that, but I don't think it was that simple. I'll try to find more references.
Oops - AC current travels more on the outer shell, DC is more evenly spread -- this is different though from coated spring steel.
A just-for-the-record answer on the tire analogy, just to satisfy the few who care…
A 2017 Corvette Grand Sport uses 285/30 19 tires on the front, 325/25 20 on the rear. That wheel choice severely limits what tires you buy. Not much either/or wiggle room left for the end user. (I didn’t even know they made a 25 series tire!) A quick search on Tire Rack shows me 2 selections, Continental Extreme Contact Sport or Michelin Pilot Super Sport. The Michelin rear tires are $483 each! before shipping and mounting. And according to my friend with the Camaro, these top of the line tires still won’t keep the car on the ground with the horsepower judiciously applied.
Sorry, no budget choices, period end of story. Sometimes that’s just the way it is. Pretty sure you can’t get by running a single tire…
Just because the light has 4 cells in parallel doesn’t mean it’s designed to run on a single cell. Obviously, there are cells that just won’t do it. A good many protected cells will cut out at the higher levels, not providing Turbo at any output level. It’s a Quad emitter light, it requires power.
+1 Dale.
Bout the spring coatings, I talked with my buddy here @work, a 30+ year design engineer, hobby rocketry, hobby ham (building and modding), etc... He said yes - spring steel is conductive and if coated properly, the steel should carry some of the current, but if the coating has better conductivity like gold, etc., it's kind of like putting 2 resistors in parallel - one high value, one low value, therefore more electricity will travel through the low value resistor - path of least resistance. From my experiences of not measuring conductance on the spring steel, it's probably a coating, whether a somewhat natural oxide coating or a non-conductive coating used to bond the outer coating layers. Now with the spring steel being thicker than the coating, yes - also helps if the electricity has a path to the steel, the thicker steel should help -- it's not just the coating. So I was somewhat right, somewhat wrong on this - least according to him. He also says obviously DC behaves different from AC, and also high voltage or high amps makes a difference in how it behaves.
I think there's tremendous variation out there with the quality of springs. The bonding, thickness, and type of materials of the coating are important and probably often overlooked. If there's a non-conductive coating on the steel for either bonding the outer coating layers or a developed oxide layer, then the spring steel isn't part of the conductance.
Thanks for the elaborate explanation on springs Tom
Dale you are right of course yet the Q8 works fine with one cell
Only using a single low drain cell with protection will cost the user the turbo mode.
And the thing is, if somebody wants to use it with 2 cells for a period of time and then wants to use four it should work just fine.
Don’t get me wrong, my tests did show it already does that but sagging springs are just not the kind of thing we would want and another slightly longer thicker spring should work just fine since Djozz and Tom both get nice high lumen on only the bigger of the two double springs now used.
This is the stage to address this for when production had started it will be a passed station.