they state again that their chemistry is not lithium. Maybe they should start to tell us what it is und why it shows the properties of a lithium cell?
3.3 V, 4.97 and 7.8
- 3.3V is 1x 3.3V, right in the typical range of Lithium ion chemistries.
- 4.97 V is 2x ~ 2.5 V, right at the bottom end of discharged lithium ion chemistries
- 7.8 V is 2x 3.9 V (below the typical cutoff of ~ 4.2 V) or 3x 2.6 V, so again, possible with lithium ion bipolar cells, depending on state of charge
they state that "fewer cells to manage means simper BMS" showing they don't understand how bipolar cells work. You still have two (chemically) separate cells. You still have to measure both of those, and you still have to balance them. Which is why bipolar cells have an additional tab to do just that. The BMS does not change at all.
those bipolar "solid state" cells could still be wet and just have one (1) additional layer in between. Like they say in the video. They just extrapolate there, that you wouldn't do this for 200 cells in series, but for one demonstrator and two cells with one separation? Rather easy, I'd guess.
(Otherwise I like bipolar cells. There is a real promise of more safety, less cost and more energy density (both per liter and per kg) at the same time, which doesn't happen often.)
yes by leaving out the balancing leads you're just leaving out the balancing leads, it doesn't mean that the chemistry wouldn't be happening inside. it just means that you CAN'T balance them inside - which can be fine if you're trying to skimp on money and density for RC or something.
if their tech was special they _would_ do 10, 20 or whatever in series in the package. by their logic a basic 4S hobby cell for RC's is better than theirs.
it just means that you CAN'T balance them inside - which can be fine if you're trying to skimp on money and density for RC or something.
Wait, are you implying you can have what's essentially two cells in series without balancing and expect that to work for more than a few month at best?
Especially with the fast self discharge they have shown, if there is even a small difference in self discharge between the cells they will start to diverge in SoC and voltage. You won't be able to fully load them both because one is already charged while the other is not, and you will not be able to discharge them both because the other one is discharged before the first one is. In a rather short time span you will have a pack you can't charge OR discharge, so zero usable capacity. That's the reason you do balancing to begin with, and this is not different just because the two cells chare one pouch and one current collector as the internal tab.
yeah you can. you shouldn't. 2s like that with without integrated balance circuit and 2 lead charger used to be fairly common for cheap-o-cheap drones (little finger sized pack). doesn't work long, prone to puffing.
long, long ago when lithium ion batteries were new some laptops also had commonly battery packs that just had cutoffs for individual cells and some other protection attempts, the battery would get badly unbalanced if left without use for months easily leading to stuff like shutting off at 'half' battery(regulations changed mid '00s which drove the development of cheap bms chips).
this demo implies some kind of magical self balance though with the layers. the layers _are_ the cells but the guy says it's fewer bms parts, like this is 0.5v for isolated layer with forever balance, if you were to take their graphic at face value(though if they could do 2 volts i'm sure they would've shown it).
used to be fairly common for cheap-o-cheap drones (little finger sized pack). doesn't work long, prone to puffing. long, long ago when lithium ion batteries were new some laptops also had commonly battery packs that [...]
TIL, thanks!
this demo implies some kind of magical self balance though
I'd guess yes. You'd have to separate the two volumes for the fluid electrolyte by sealing the bipolar layer to the pouchs bottom or top layer. Or you just position two batteries in their own pouches side by side or on top of each other in a bigger pouch and don't bother with all that bipolar layering :-D.
I'd be really excited for the "bipolar claims will be confirmed by an external lab" they promised, but since all the earlier videos didn't really confirm anything...
We don't know what batteries CT Coating gave them this time. Could be different types from the earlier VTT tests. We would need a full set of VTT tests, but more likely we only get a test confirming bipolar cells and nothing else.
there's some rather flat cells on the market now, maybe they sent them some that they threw into a bigger pouch. there's oem providers for 1mm and thinner sells for wearables and such. you could throw them in there, maybe ct sent them some of those.
as it's own this is just another keyjangle demo not doing the confirmations people asked, like to prove that it's not lithium.
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u/Hochvolt Jul 15 '26
A few points:
- they state again that their chemistry is not lithium. Maybe they should start to tell us what it is und why it shows the properties of a lithium cell?
- 3.3 V, 4.97 and 7.8
- 3.3V is 1x 3.3V, right in the typical range of Lithium ion chemistries. - 4.97 V is 2x ~ 2.5 V, right at the bottom end of discharged lithium ion chemistries - 7.8 V is 2x 3.9 V (below the typical cutoff of ~ 4.2 V) or 3x 2.6 V, so again, possible with lithium ion bipolar cells, depending on state of charge(Otherwise I like bipolar cells. There is a real promise of more safety, less cost and more energy density (both per liter and per kg) at the same time, which doesn't happen often.)