Supercapacitors / Ultracapacitors

Nope. I calculated the kinetic energy. That's the MOST you can get by stopping a moving vehicle. Pushmi seems to think in practice you only get 35% of this, in practice. This figure would not surprise me.

 

You failed to finish the sentence: That's the most you can get* by stopping a moving vehicle ONCE.

*theoretically, but not practically, due to thermodynamic limits

Amazingly enough, most systems installed in a car's powertrain get used many times over the lifetime of a car. Trying to calculate the advantage (or lack thereof) based on a single use... well, do we really need to point out how ridiculous that is?

Looks like you're just "playing dumb" again, Martin. I don't believe you are actually that clueless.

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Actually he did cite the theoretical number (rounded off a bit) for the energy required to accelerate the mass he indicated to the speed he indicated, but only at the simplified level of a public school physics problem. He ignored air resistance, which as most of us know is quite significant when accelerating a car to highway speed.

Not a lot of call for passenger cars that drive in a vacuum...

But Martin is correct to point out that certain other factors (such as air resistance) represent unrecoverable losses.

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Hi...i am a new user here. As per my knowledge all supercapacitors is that they are low voltage devices - typically 2.7v although these hydrophilic ones will go up to 4 volts I think. Certainly, conventional supercaps are destroyed if you allow the voltage across it to exceed this. In a series string of them, this can easily happen so each cell has to have a shunt circuit which clamps the voltage across it to below the maximum voltage.

 

I imagine that as BEVs become the standard on the road, manufacturers will build cars with quickly exchangable batteries. So instead of plugging your car in to refill it, you would drive your car into the "station" and your battery would be robotically exchanged with a fully charged one.

This way all of the danger you describe is avoided.

All of the electrical infrastructure to that "filling" station is still necessary, but that's (somewhat) easier to handle. In addition the battery recharging could be done at a location right next to a power generation plant and the batteries could be delivered to the "filling" station just like gasoline is delivered today.

Peace,
Randy

 

There was a company called (Project) Better Place which promoted that scheme. It quickly went bankrupt, as the startup costs (for building multiple expensive robotic battery swap stations, and stocking them with multiple expensive spare battery packs) are much too high to be amortized by any reasonable monthly payment. BP's monthly subscription price was so high that it wiped out the advantage of electricity being cheaper than gasoline to power your car.

Tesla Motors also tried battery swapping on a trial basis. That was also a flop. Most customers who tried it out didn't ever do it again. One of the problems is that most EV owners want to own their car's battery pack; they want it to be part of the car, not something they just rent. That means if you use a battery swap station, you have to return to the same station later to get your original pack back. Apparently most Tesla customers found that to be an inconvenience.

In summary, it seems that battery swapping in EVs is a solution that few people find worth the bother. And with the range of EVs increasing with each new generation, plus the recharge time decreasing, it won't be many years before nobody is going to have any reason to want to swap battery packs on a new EV.

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In this thread we are talking about revolutionary and/or theoretical supercaps which will handle much, much higher voltages. If supercaps can't handle more than 3 volts, if exposing them to higher voltage will actually blow them out, then obviously stringing them together in series to increase the voltage (and power) to something useful in powering an EV will never work.

 

I understand all of your points. I wasn't thinking that I was "renting" the battery or signing up for a subsription to a "battery replacement service". I would drive into a *any* battery station and exchange my empty battery with a full one. All I have to pay for is the electricity that's in the new battery...plus any service or delivery charges. I realize I don't have all the answers, but don't tell me that this will never happen just because the first few business models didn't work out. That's short sighted.

Although, I hope that you're correct about your last statement. That could be the best end result.

 

In addition, the other problem will be the proliferation of battery types and designs which will lead to an inventory nightmare at the charging station. Just take a cell phone chargers as an example. Every manufacturer has their own type of charger cable as they claim their batteries are different. Similarly, each manufacturer of EVs will have certain unique customization and will insist only their batteries be used. If there are 15 manufacturers with 5-7 configurations each, you are talking about a 100 different SKU's to be held in each station, unless someone can force standardization. On the other hand for battery, I would not want to swap an old Panasonic for a new Samsung and so on. So battery swaps will work only if we have standardized batteries, limited choices and people are willing to lease batteries instead of owning them. Also what about warranties, how will that be tracked on the battery.

Battery swaps will work only for large fleet customers. For example, a bus line, where there are say 200 buses or more, they can afford to invest in swapping. When a bus comes in, you swap the battery and put a charged one in. So during the time the bus is operational, a spare is being charged. This will keep the up time on the buses and also reduce the number of chargers required.

 

I documented two EV trips to Nashville:

• Using fast DC charger: https://insideevsforum.com/community/index.php?threads/benchmark.3199/
• Using an L2 charger: https://insideevsforum.com/community/index.php?threads/benchmark.3199/#post-31202

There are separate problems with today's CCS and J1772 chargers:

• Extra distance and unreliable - the fast DC, CCS chargers are rare which means a significant detour, ~30 out of ~112 miles, to reach Nashville. Worse, only 1 of 4 stations worked on my last visit and I had figure out which one.
• Unreliable and slow - the first L2 charger was broken which calling Blink support confirmed. The second one at a Nissan dealer, was free but only during business hours. The limited charging rate, 24A, meant taking 1h 25m to get enough charge with a 10 mile margin to reach Nashville. My car can charge at 31A so it took ~20 min longer than it would with a full power, 40A, charger.

As for supercars, their advantage of insanely fast charge and discharge only makes sense:

• Traction motor(s) sized high enough to provide full regenerative braking energy in emergency stop.
• Batteries limited charge rate that needs to be protected from full braking energy.

You would need an asymmetrical battery chemistry that handles full rated discharge but has to be charged at a slower rate. Not impossible, highly unlikely.

Bob Wilson

 

I've argued for the theoretical possibility of using this business model for BEV semi tractors, for large fleets running trucks frequently on regular routes. Battery swap stations could be spaced along those routes, to provide up to coast-to-coast range. (Presumably all trucks which use the swap stations would be using the same type of battery pack.) The economics for that might work... or might not. It would certainly increase the problem with logistics, in making sure that every tractor would find a fully charged battery at the swap station.

However, Tesla didn't even mention the possibility in its promotion for the Tesla Semi Truck, so I guess Tesla thinks it's not a practical solution.

I'm not claiming it would actually be practical, in the economic sense, but I think the idea is worthy of discussion. Certainly it's possible in the engineering sense.