Hillhater said:
Unless you have evidence to the contrary, i would suggest that those Boston Power cells are simply a pair of 18650's parallel'd together in a neat wrapper !
Even if they are something else, they have the same capacity , size and performance as 2 18650's ?
...with the 18650 is not like Tesla is packing them as close together as possible. The main reason they are spaced is to play it safe (car crash)
hmm,.. and i thought it was so they could get the essential cooling system tubes in between the cells ?
Those are really oval wrapped, not just a pair of 18650's, I've cut them apart myself. They are also a remarkably safe cell from my testing (shorting, smashing, mild-overcharge, mild-reverse charge, puncture all resorted in nothing more than getting warm and a little whisp of smoke here and there).
bobc said:
Interesting thread. Aside from fitting snugly into flashlights & sex toys, the round can is pretty much the best shape for containing pressure, might be a practical reason for its popularity?
FWIW I'd be surprised if there were a massive revolution in any of the EV technologies in the next 5 to 10 years, but I reckon the cost & performance will improve gradually while fossil fuels gradually get more pricey.
I still argue with folk who say "the EV will never be taken up en masse until it's better reg. range than an ICE car". Talk to me about it in 15 years when it costs a month's wage to fill your tank....... The freedom to drive 1000 miles on a whim at the drop of a hat is SUCH a luxury!
If you're making pressure in your cell, that's the problem not the container, and no practical (light and economical) container can hold back the pressures involved with a cell failure reguardless of the shape or topology anyways. Whats scary about 18650's is because the shape is a good pressure vessel, when the vent's don't function as designed (which often happens to people who foolishly solder them etc) they can build to hazardous pressures before exploding with shrapnel. You fortunately don't have that failure mode with pouches etc.
LockH said:
"sex toys"? (Dang, got that ebiker guys woodie again.)
Always glad to help my friend.
flathill said:
at least doesn't have sharp bends like prismatics,
To the contrary. 18650's and those cells have very tight bend radius as they get towards the center. It really cracks away coating from the foils to become inactive as well (unless it's super binder doped, but that costs energy and power density etc).
In a proper die-cut pouch/prismatic cell layout (LG chem is the singular type I'm aware of that folds there pouch cells, but many thundersag-esque prismatics are rolled), the foils have zero bends at any point unless you choose to bend the whole pouch after you make it for some reason.
There are so many exciting new cell technologies being developed right now. Between solid state electrolytes slowly starting to get sorted out and various non-lithium based chemistry options along with promising super high energy anode tech from sulfur to silicon, and the various graphene current collector grid tech and 3d nano-wire tech, it's anyways guess what the next generation of batteries will look like.
Here's to hoping they are made on continuous film lamination machines using all solid materials and we drop the whole can/sack/pouch/shell concept finally and open up huge flexibility in form-factor and packaging density and cost reduction.
Also, the concept of a battery that requires a cooling/heating system is a preposterous band-aid as well. How about batteries that simply perform well over the practical range of temps a vehicle will be in, and have low enough impedance that they don't waste so much energy they require being cooled while you charge/discharge them.
Sky is the limit. Develop outside the box (can/sack etc).