5 ms·

Here's my first thought: Put both supercapacitors and batteries in an electric car. The supercapacitors can help greatly in a couple of ways. When doing a fast

Here's my first thought: Put both supercapacitors and batteries in an electric car. The supercapacitors can help greatly in a couple of ways. When doing a fast charge, the supercapacitor bank can absorb the energy super fast, much faster than a bank of batteries could. Then a microcontroller could control the transfer of that power more gradually over to the battery. (Unfortunately, super capacitors, when I last read something about it, could only hold their charge for 4 days or so, so they couldn't replace batteries themselves.) Perhaps this could be the key to the 5 minute recharge for cars? Second, supercapacitors could also save some wear and tear on the batteries during rapid acceleration and regenerative charging.

kevin_b_er 8y ago
For this to work you'd need as much capacity in supercaps as in batteries. In that case you'd want to use that capacity, except it self-drains. The UX would be strange and difficult to manage. EDIT: The above comment was meant about supercharging, not regenerative braking.
- throwaway5752 8y ago
  No it wouldn't! You could preferentially store the regenerative braking energy into the ultracapacitors (and discharge from them from a stop, instead of the main battery). You're not talking a huge number of them (order of magnitude of ~100) for a cycle brake cycle at Model 3 mass, highway speed, and normal braking.
- LeifCarrotson 8y ago
  You wouldn't need an equivalent capacity in supercaps as batteries, only as much as the vehicle can use or create in a short amount of time. The UX would be invisible: If demand is greater than the supply available from the battery pack, drain some energy from the supercapacitors. If it's less, gradually shift some energy into them. If the driver is not in the vehicle, drain it all out, when they come back, recharge the supercaps. The problem is that these capacitors and transfers add cost money, space, weight, energy, and complexity. Looking at some numbers, batteries are ~20x more energy dense in both volume and weight. Batteries have 1/10th the power density, but efficiency drops significantly with discharge rate and they have fewer lifetime charge cycles and poorer temperature response. Batteries also have much, much lower self-discharge, and cost a lot less per kilowatt-hour. Right now, lithium-ion batteries are simply good enough and supercapacitors are not that much better, so it's the cost-benefit analysis says it's better to take the costs you would have spent on supercaps and just put in a few more batteries. That balance could shift, though, with improvements in supercap technology, or - paradoxically - with improvements in battery chemistry. If a battery with much better energy density and/or lower cost was found, with a reduced discharge rate that was sufficient to cruise but insufficient to accelerate or do regenerative braking, you could add supercaps to make a vehicle based on that battery feasible. It's similar to the electric grid - the base load would be handled by the slow batteries, similar to coal or nuclear power plants, while peaking loads would be handled by the supercapacitors, like a gas turbine.
  - kevin_b_er 8y ago
    I agree this could work with regen, but not for "supercharging".
spectrum1234 8y ago
This is an interesting idea. Is this really possible though? Is it just a cost challenge? I admittedly haven't read up a ton on fast charging options but I also don't think I've seen super-capacitors mentioned as an intermediary source in any discussions. Given the article mentions Maxwell wanting to get into the automotive industry, a fast charging use is probably still a long ways out at this point.
flexie 8y ago
How much space would sufficient supercapacitors require and would they be heavy? Would it add significantly to the cost of a car?
- joseflavio 8y ago
  It seems they are quite light, at least according to this guy who built a home-made hybrid car battery using super capacitors: https://www.youtube.com/watch?v=VJhJ5TfQ6DU https://www.youtube.com/watch?v=VJhJ5TfQ6DU
- Scoundreller 8y ago
  Or could they even be structural and offset some other components’ weight.
toomuchtodo 8y ago
Tesla just filed a patent for a new battery chemistry out of their Nova Scotia R&D facility that supports faster charging and superior longevity. I expect batteries to become supercapacitors faster than supercapacitors become batteries. If supercapacitors have any role, it’s at EV charge stations to reduce demand charges from utilities. VW just agreed to buy a whole lot of Tesla batteries for this purpose at their Electrify America charge stations. Space is not an issue, as you can bury your storage under the charger stalls.
- solarkraft 8y ago
  > If supercapacitors have any role, it’s at EV charge stations to reduce demand charges from utilities Especially here I'd expect batteries to win out as transfer capacity is roughly proportional to storage capacity with batteries.
Symmetry 8y ago
For a capacitor to be used in charging that way it would have to have something like the same capacity as the car's battery. Supercapacitors tend to have lower specific energy density than batteries do so this would require reducing the car's range by something like a factor of 5. A capacitor much smaller than the batteries acting as a buffer for rapid acceleration and braking might make sense, though.
- briffle 8y ago
  I could see it used for the superChargers, so they could have more chargers feeding off a smaller power connection. (especially for the ones needed for the semi).
  - newnewpdro 8y ago
    This is far more plausible, where space is abundant outside the vehicle to keep a cache of supercaps to charge from. Especially if the usage pattern tends to be very bursty. But if the superchargers are (or will be) continuously near 100% utilization it's pointless, they'll need the current at the mains.
  - extrapickles 8y ago
    I doubt they will be used for either side of charging. Super/Ultra capacitors cost a lot more than batteries per watt hour.
    - hinkley 8y ago
      Why not in the charge control circuitry in the supercharger? Don’t those use some pretty big caps?
    - jws 8y ago
      In the context of a Supercharger the critical metric would probably be cost per charge/discharge cycle for a given capacity bank. While a car probable averages a fraction of a charge cycle per day, a busy supercharger might be on the order 10 cycles per day. Super capacitors degrade more slowly than batteries with cycles. The use which might make sense is to use the capacitors to supplement the grid supplied power during the initial fast charge phase, then in the slower final charging phases or idle time recharge the capacitors from the grid for the next customer. This levels out the demands on the grid and can result in a lower electricity rate from the power company. It all depends on the constants if it makes sense. Or maybe it doesn't make sense and Tesla needed something out of Maxwell's patent portfolio.
agent86 8y ago
The trouble spot with Superchargers is usually the end of the charge, not the beginning. The batteries can usually absorb energy rather quickly when at a low rate of charge. What is really painful is the last 10% where the charge rate drops line a stone. What would be an interesting use of this idea would be to have 10% capacity onboard in capacitors. Once you get within 10% of the desired charge level in the batteries, you quickly charge the capacitors, which then trickles into the battery over time. This might allow you to increase the overall charge rate for the car which would help reduce wait times at Superchargers.
- tedsanders 8y ago
  Far better would be to add 10% battery capacity, which would have the same net effect for cheaper. If you're not going to be using the high power of a supercapacitor, there's zero reason to pay a premium.
  - agent86 8y ago
    The trouble with that is to a certain extent we're just kicking the can down the road. Modern Tesla vehicles have more range than older ones, yet people still charge modern ones to 100% for various reasons. The idea here is to leverage their incredibly fast rate of charge and short term nature to reduce time spent Supercharging. Very roughly speaking, you can charge from 0-90% in an hour, but to go from 90-100% can take almost another hour. If you could get the car to 90% and then very rapidly charge the capacitors with the remaining 10% that trickles in, you get the car off the charger faster. In theory you could almost double the number of cars you could serve at that station.
    - toomuchtodo 8y ago
      Tesla is rolling out a firmware update that will prevent you from charging above 90% at high contention Superchargers. Simple solution.
    - Dylan16807 8y ago
      That's just lying to yourself about what "100%" is, by excluding the caps. It's again easier to add more battery and pretend it doesn't exist for reaching 'full charge'. That will also give you better battery longevity.
agumonkey 8y ago
I think car brands are already designing hybrid power circuits. The benefits of low resistance caps as small bursts / buffer, and avoiding wearing the usual li-ion banks is too good to pass on.

kevin_b_er 8y ago

For this to work you'd need as much capacity in supercaps as in batteries. In that case you'd want to use that capacity, except it self-drains. The UX would be strange and difficult to manage. EDIT: The above comment was meant about supercharging, not regenerative braking.

throwaway5752 8y ago
No it wouldn't! You could preferentially store the regenerative braking energy into the ultracapacitors (and discharge from them from a stop, instead of the main battery). You're not talking a huge number of them (order of magnitude of ~100) for a cycle brake cycle at Model 3 mass, highway speed, and normal braking.
LeifCarrotson 8y ago
You wouldn't need an equivalent capacity in supercaps as batteries, only as much as the vehicle can use or create in a short amount of time. The UX would be invisible: If demand is greater than the supply available from the battery pack, drain some energy from the supercapacitors. If it's less, gradually shift some energy into them. If the driver is not in the vehicle, drain it all out, when they come back, recharge the supercaps. The problem is that these capacitors and transfers add cost money, space, weight, energy, and complexity. Looking at some numbers, batteries are ~20x more energy dense in both volume and weight. Batteries have 1/10th the power density, but efficiency drops significantly with discharge rate and they have fewer lifetime charge cycles and poorer temperature response. Batteries also have much, much lower self-discharge, and cost a lot less per kilowatt-hour. Right now, lithium-ion batteries are simply good enough and supercapacitors are not that much better, so it's the cost-benefit analysis says it's better to take the costs you would have spent on supercaps and just put in a few more batteries. That balance could shift, though, with improvements in supercap technology, or - paradoxically - with improvements in battery chemistry. If a battery with much better energy density and/or lower cost was found, with a reduced discharge rate that was sufficient to cruise but insufficient to accelerate or do regenerative braking, you could add supercaps to make a vehicle based on that battery feasible. It's similar to the electric grid - the base load would be handled by the slow batteries, similar to coal or nuclear power plants, while peaking loads would be handled by the supercapacitors, like a gas turbine.
- kevin_b_er 8y ago
  I agree this could work with regen, but not for "supercharging".

spectrum1234 8y ago

This is an interesting idea. Is this really possible though? Is it just a cost challenge? I admittedly haven't read up a ton on fast charging options but I also don't think I've seen super-capacitors mentioned as an intermediary source in any discussions. Given the article mentions Maxwell wanting to get into the automotive industry, a fast charging use is probably still a long ways out at this point.

flexie 8y ago

How much space would sufficient supercapacitors require and would they be heavy? Would it add significantly to the cost of a car?

joseflavio 8y ago
It seems they are quite light, at least according to this guy who built a home-made hybrid car battery using super capacitors: https://www.youtube.com/watch?v=VJhJ5TfQ6DU https://www.youtube.com/watch?v=VJhJ5TfQ6DU
Scoundreller 8y ago
Or could they even be structural and offset some other components’ weight.

toomuchtodo 8y ago

Tesla just filed a patent for a new battery chemistry out of their Nova Scotia R&D facility that supports faster charging and superior longevity. I expect batteries to become supercapacitors faster than supercapacitors become batteries. If supercapacitors have any role, it’s at EV charge stations to reduce demand charges from utilities. VW just agreed to buy a whole lot of Tesla batteries for this purpose at their Electrify America charge stations. Space is not an issue, as you can bury your storage under the charger stalls.

solarkraft 8y ago
> If supercapacitors have any role, it’s at EV charge stations to reduce demand charges from utilities Especially here I'd expect batteries to win out as transfer capacity is roughly proportional to storage capacity with batteries.

Symmetry 8y ago

For a capacitor to be used in charging that way it would have to have something like the same capacity as the car's battery. Supercapacitors tend to have lower specific energy density than batteries do so this would require reducing the car's range by something like a factor of 5. A capacitor much smaller than the batteries acting as a buffer for rapid acceleration and braking might make sense, though.

briffle 8y ago
I could see it used for the superChargers, so they could have more chargers feeding off a smaller power connection. (especially for the ones needed for the semi).
- newnewpdro 8y ago
  This is far more plausible, where space is abundant outside the vehicle to keep a cache of supercaps to charge from. Especially if the usage pattern tends to be very bursty. But if the superchargers are (or will be) continuously near 100% utilization it's pointless, they'll need the current at the mains.
- extrapickles 8y ago
  I doubt they will be used for either side of charging. Super/Ultra capacitors cost a lot more than batteries per watt hour.
  - hinkley 8y ago
    Why not in the charge control circuitry in the supercharger? Don’t those use some pretty big caps?
  - jws 8y ago
    In the context of a Supercharger the critical metric would probably be cost per charge/discharge cycle for a given capacity bank. While a car probable averages a fraction of a charge cycle per day, a busy supercharger might be on the order 10 cycles per day. Super capacitors degrade more slowly than batteries with cycles. The use which might make sense is to use the capacitors to supplement the grid supplied power during the initial fast charge phase, then in the slower final charging phases or idle time recharge the capacitors from the grid for the next customer. This levels out the demands on the grid and can result in a lower electricity rate from the power company. It all depends on the constants if it makes sense. Or maybe it doesn't make sense and Tesla needed something out of Maxwell's patent portfolio.

agent86 8y ago

The trouble spot with Superchargers is usually the end of the charge, not the beginning. The batteries can usually absorb energy rather quickly when at a low rate of charge. What is really painful is the last 10% where the charge rate drops line a stone. What would be an interesting use of this idea would be to have 10% capacity onboard in capacitors. Once you get within 10% of the desired charge level in the batteries, you quickly charge the capacitors, which then trickles into the battery over time. This might allow you to increase the overall charge rate for the car which would help reduce wait times at Superchargers.

tedsanders 8y ago
Far better would be to add 10% battery capacity, which would have the same net effect for cheaper. If you're not going to be using the high power of a supercapacitor, there's zero reason to pay a premium.
- agent86 8y ago
  The trouble with that is to a certain extent we're just kicking the can down the road. Modern Tesla vehicles have more range than older ones, yet people still charge modern ones to 100% for various reasons. The idea here is to leverage their incredibly fast rate of charge and short term nature to reduce time spent Supercharging. Very roughly speaking, you can charge from 0-90% in an hour, but to go from 90-100% can take almost another hour. If you could get the car to 90% and then very rapidly charge the capacitors with the remaining 10% that trickles in, you get the car off the charger faster. In theory you could almost double the number of cars you could serve at that station.
  - toomuchtodo 8y ago
    Tesla is rolling out a firmware update that will prevent you from charging above 90% at high contention Superchargers. Simple solution.
  - Dylan16807 8y ago
    That's just lying to yourself about what "100%" is, by excluding the caps. It's again easier to add more battery and pretend it doesn't exist for reaching 'full charge'. That will also give you better battery longevity.

agumonkey 8y ago

I think car brands are already designing hybrid power circuits. The benefits of low resistance caps as small bursts / buffer, and avoiding wearing the usual li-ion banks is too good to pass on.