4680 cell lights
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WalkIntoTheLight
Flashlight Enthusiast
I dunno. That's even fatter than a D cell. But, when I measure my BLF Q8, its body is fatter than 2", so I can see the 4680 being useful in a light like that. Assuming the 4680 can deliver high current.
idleprocess
Flashaholic
I would sure like to see what the 4680/46800 cell can do.
I did some theorycrafting a while back:
Spitballing, but assuming average Ah/cm™ relative to other high-density 18650/26650/21700 cells, I guesstimated 25Ah in that formfactor for high-density cells.
The initial peak current estimate for a potential high-power cell using a similar metric (peak current per cm³) relative to other high-power 18650/26650/21700 cells was ... almost certainly unrealistic. Even scaling by the surface area:volume ratio relative to 18650 the peak current value was still seems unreasonable.
Reality is that any 4680s produced for Tesla will be principally high-density cells. High-current versions on the same order as 18650/26650/21700 seem a bit unlikely to emerge - the low surface area:volume ratio is not conducive to heat removal.
2C would be a good discharge rate for a high-density version, meaning that such a cell could hypothetically spit out approximately 180 watts for 30 minutes. I could certainly handle a stubby ~1D formfactor light with ~90Wh on tap - even a 1C peak discharge would be more power than most high-power cells can deliver and that level of discharge is unlikely to stress the 4680 very much. 2 in series would be spectacular.
I've seen some sources bafflingly claim 9Ah for the 4680, but that would be a huge step backwards on density, the exact opposite of Tesla's goal with a mere 31kWH pack (960 * 3.6V * 9Ah) - merely ~2x a 21700's capacity while being ~5x times the volume. Reversing Sandy Munro's math, I get slightly more than 25Ah:
I did some theorycrafting a while back:
Spitballing, but assuming average Ah/cm™ relative to other high-density 18650/26650/21700 cells, I guesstimated 25Ah in that formfactor for high-density cells.
The initial peak current estimate for a potential high-power cell using a similar metric (peak current per cm³) relative to other high-power 18650/26650/21700 cells was ... almost certainly unrealistic. Even scaling by the surface area:volume ratio relative to 18650 the peak current value was still seems unreasonable.
Reality is that any 4680s produced for Tesla will be principally high-density cells. High-current versions on the same order as 18650/26650/21700 seem a bit unlikely to emerge - the low surface area:volume ratio is not conducive to heat removal.
2C would be a good discharge rate for a high-density version, meaning that such a cell could hypothetically spit out approximately 180 watts for 30 minutes. I could certainly handle a stubby ~1D formfactor light with ~90Wh on tap - even a 1C peak discharge would be more power than most high-power cells can deliver and that level of discharge is unlikely to stress the 4680 very much. 2 in series would be spectacular.
I've seen some sources bafflingly claim 9Ah for the 4680, but that would be a huge step backwards on density, the exact opposite of Tesla's goal with a mere 31kWH pack (960 * 3.6V * 9Ah) - merely ~2x a 21700's capacity while being ~5x times the volume. Reversing Sandy Munro's math, I get slightly more than 25Ah:
- Model 3/Y 21700 : 75kWH pack / 4416 cells = 16.68 Wh / 3.6V = ~4.7Ah
- Model 3/Y 4680 : 87kWk pack (16% more range = 16% more energy) / 960 cells = 90.63 Wh / 3.6V = ~25.2Ah
idleprocess
Flashaholic
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Tesla was saying their new cells are specifically designed for high Amp currents.
Would I want a 2 x 46800 light?? no , yes , no , kinda
With the 4.6x reduction in cell count, they need at least that increase in absolute current per cell. But they still need good energy density for range.
I can see using a 4680(0) battery in a light but only with an on board protection circuit. A shorted battery of that size is like a hand grenade.
I wouldn't mind a few of them in series to replace the lead acid monster in my car though; or maybe an e-bike.
I wouldn't mind a few of them in series to replace the lead acid monster in my car though; or maybe an e-bike.
ChrisGarrett
Flashlight Enthusiast
Who the hell needs a light with that big a cell and no true upside in current handling?
Buy a couple of Sony 5As and call it a day with whatever light you choose.
Chris
idleprocess
Flashaholic
Slapping an 18650 protection circuit limited to 2-3A would be dumb. However considering the likely capacity of 25Ah, limiting such a beast to mere 1C would still mean 90W of output potential.
Hooked on Fenix
Flashlight Enthusiast
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- Dec 13, 2007
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Sounds like a nice cell to make a 12 volt battery for a really bright h.i.d. spotlight or even a compact l.e.p. (light emitting plasma) light.
ChrisGarrett
Flashlight Enthusiast
I'm not saying that there aren't applications out there, for some people, just that personal lighting apps probably aren't that practical and as somebody who has two Emisar D4s and a 3Tronics triple, we're already on the cusp of the 'thermal apocalypse.'
Chris
WalkIntoTheLight
Flashlight Enthusiast
Well, some lights, like the BLF GT, take eight 18650 cells. A couple of 4680 cells would actually make some sense in that kind of large light.
idleprocess
Flashaholic
The difference in heat management between the D4 and D4S is significant, with the D4S managing not only longer time at peak output but also a greater sustained output. The step up from 18mm to 26mm is slightly more than double the surface area; if we assume a head height equal to the radius the volumetric difference is a bit more than triple. Applying the same metric to 46mm, the surface area is ~3.1x and ~6.5x between 26mm and 18mm respectively with the nominal volumetric difference being ~5.5x and ~16.7x. While this won't scale in a neat linear fashion to passive power dissipation ability, it does suggest that a simple increase in size with resultant additional thermal mass will allow for prolonged operation at significantly higher power than smaller lights.
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If you have a three SBT 90.2 setup only running off 8.4V*, you'll need big amps, maybe 20A
Improved heatsinking efficiency, boards, wiring, everything, needs to be more robust & you'll have one incredible searchlight.
*from two 46800 in series.
If you have a three SBT 90.2 setup only running off 8.4V*, you'll need big amps, maybe 20A
Improved heatsinking efficiency, boards, wiring, everything, needs to be more robust & you'll have one incredible searchlight.
*from two 46800 in series.
idleprocess
Flashaholic
Google says the Model 3 can deliver a maximum 371 kW to the motors. Using the back-of-the-napkin figures in post #3:
- Model 3/Y 21700 : 371kw / 4416 cells = 84 W / 3.6 = 23A
- Model 3/Y 4680 : 371kw / 960 cells = 386 W / 3.6 = 107A
idleprocess
Flashaholic
From what I read up on their 4680 design, it's conventional li-ion tech with some evolutionary improvements to the existing recipe. Different manufacturing methods allow for a modest increased in density and a nice bump in power delivery so they can greatly reduce cell count per pack.
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I started this thread last August:: https://www.candlepowerforums.com/vb/showthread.php?470047-Battery-advancements-thread&
I started this thread last August:: https://www.candlepowerforums.com/vb/showthread.php?470047-Battery-advancements-thread&
n3eg
Newly Enlightened
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Tesla was saying their new cells are specifically designed for high Amp currents.
Would I want a 2 x 46800 light?? no , yes , no , kinda
You could smack someone upside the head with it like a Streamlight.
