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Will Tesla hybridise its batteries with Supercapacitors already?!

Will Tesla hybridise its batteries with Supercapacitors already?!

We understand that supercaps are way low on energy density, but what about their power density?! It's HUGE!
What about their efficiency?, exemplary!
Lifespan?, one million charge/discharge cycles!
So.. what's going on then? Any ideas?

Benefits of incorporating supercaps in an electric vehicle ( in my humble opinion) are:

1. Increased lifespan of battery cells due to a flatter discharge graph line ( this also means you can rebalance energy vs. power when formulating your battery cell toward more energy, 100 kWh battery for the Model S or X is not far fetched).

2. Much more efficient regenerative braking ( supercaps' low ESR means that they will accept much higher currents than li-ion cells, especially when your electronics layout has a "Joule thief" configuration function, the vehicle will recapture 100% of its kinetic energy, all the way down to 0 mph, no friction brakes required).

3. A 1000+ hp quad-motor drivetrain is more than welcomed by the sheer power momentarily provided by the supercap modules)

I can go on and on about this, but let's stop at this much.

David N | 21 mai 2015

I can sense your enthusiasm for better batteries. Please understand this issue has come up multiple times in recent years. JB Straubel is well aware of supercaps. If and when current battery technology can be improved, Tesla will be all over it. If it was as easy as you make it seem, why doesn't every automaker use it.
Nice thought, but trust that Tesla is constantly looking at improving battery technology.

Timo | 22 mai 2015

1000HP is roughly 745kW. 745kW/85kWh ~= 8.8C batteries. There are 60C batteries around.

You can get a car with way over 1000HP with just changing battery chemistry. 85kWh battery with 60C discharge capacity would translate to 5100kW or 6800HP. Power is not a problem for BEV:s.

Supercaps are cool, but harsh reality is that they simply are not needed. KISS -principle denies them.

Grinnin'.VA | 22 mai 2015

My understanding is that the current stae-of-the-art for capacitators falls short of matching Tesla's 85-kWh battery for use in powering BEVs.

1. It's hard to charge them to hold as much energy.

2. They 'leak' energy too fast.

Please correct me if this doesn't fairly characterize the crux of the matter.

Earl and Nagin ... | 22 mai 2015

@Grinnin'
The short coming of capacitors is low specific-energy, ie Watt-hours/kg. In english: a pound of capacitors don't carry as much energy as a pound of batteries.
Therefore, a 1,000 lb battery in a Tesla can carry 85 kWhrs while a 1,000 lb capacitor array would only carry perhaps 10 kWhrs (amount may vary).
Where capacitors excel is in specific power (Watts/kg) or power density (Watts/liter). It will take a lot more batteries to get the power output of a capacitor array.
The thing about Tesla is that they put so many batteries in their cars in order to get good range that they naturally have a lot of power (Watts) available anyway. This reduces the value a hybrid battery would add to get more power (691 hp is probably enough for most people :-) .
One place I can see that a capacitor might help is in regenerative braking efficiency. One might be able to increase the amount of energy recovered by dumping it into capacitors instead of a battery. I doubt, however, that the extra expense of capacitors and the complex power electronics they would require would be worth it. It might add a few more miles of range but only us efficiency geeks would appreciate it (and I don't know that even I would pay for it). Adding a few more batteries would probably be a cheaper way to increase the range if you were going to add a bit more weight to the car.

EcLectric | 22 mai 2015

This is a good subject for discussion.

There are two ways that adding caps could help an electric car's range. Increase volumetric (energy/volume) or gravimetric (energy/weight) energy density, or increase overall efficiency.

The first way doesn't work because if a battery has better energy density (which in this case it does), then any shift toward caps just makes the overall energy density worse by comparison.

The second way is possible, but unlikely. You can increase efficiency by reducing the amount of heat produced by the car. That is where the energy from your battery is going. All of that energy (unless you end up at a higher altitude) is going into heating the air:

- Moving the air
- Friction with the air
- Brakes (which heat the air)
- Heating wires/motor/batteries in the car (electric friction)

I don't know about anyone else, but I hardly ever use the brakes. My car has over 40K miles on it and the brakes still squeak. I only use them to stop from about 2 MPH. Since energy is proportional to speed squared, this is not a lot of energy.

In addition, I think the limitation on the regenerative braking has nothing to do with there being any limitation in changing the battery. If the battery can accept the charge from braking 60 to 40 MPH, it can certainly accept the charge from 2 to 0 MPH.

The one area where caps might help is with battery calendar life. If a significant portion of the damage to a given battery is due to large power requirements at certain short intervals of time or due to constant discharging and recharging from regenerative braking, then adding caps could increase the lifespan of the battery, which might make them worth adding. I don't think the electronics required in adding them would be complex, but the extra calendar life would have to be worth the expense of adding a new major part to the drivetrain.

EcLectric | 22 mai 2015

I also agree that adding caps might allow the selection of batteries with better energy density that might not have a high enough power density to work without caps. The down-side of this approach is that at the track, you're going to quickly 'run out of cap' and be running on pure battery, which would not compete well. In this case, a hybrid battery might work better in a lower-end car that nobody would want to race.

Red Sage ca us | 22 mai 2015

Earl and Nagin wowed us with, "...691 hp is probably enough for most people..."

LOLoLOLoLOL! You get a +33.33³ UP for that one! True mastery of understatement, at its finest!

;-)

Earl and Nagin ... | 22 mai 2015

@EcLectric,
For racing, the capacitors might only need to store the braking energy needed to slow enough to enter a curve and maybe the amount of acceleration energy required to get back up to speed coming out. That might not be too bad.
Of course this would be for ultimate performance -- When 691 hp isn't enough :-)

carlgo2 | 23 mai 2015

Flywheels can do that also. Fantastic boost coming out of corners. They, and perhaps capacitors, could also be used to even out the power flow. I found on an i3 site that the biggest problem with that car's tiny battery was constantly having to regain speed as when traffic slows. The key to the longest possible range was to keep the speed up!

So, a capacitor or flywheel's energy might only be used to regain speed and thus take that drain off of the main battery. Of course just having a better battery would be simpler.

Red Sage ca us | 23 mai 2015

+37035.9259!

blue adept | 4 juin 2019

@TerryMulhern

I'm guessing that it hasn't occurred to you (or, by all appearances, anyone else for that matter) that Tesla might've acquired the capacitor technology to, perhaps, augment its Powerwall stationary energy storage facilities which, all things considered, could be a good fit...?

blue adept | 4 juin 2019

Other than that it's nice to see everyone thinking and really putting some brain to potential range/power increase possibilities.

+1 @EcLectric

TeslaTap.com | 5 juin 2019

TerryMulhern above is a spam bot where it grabs text from elsewhere, modifies it, adds a link that seems ok, and sticks in the spam link. One clue is posting to a 4 year old thread. Flag.

Maxwell Tech sold off the Ultracapacitor business before Tesla bought them. So Maxwell was bought for battery tech, not Ultracapacitors.

blue adept | 5 juin 2019

Good to know!