4 ms·

Could this be used to charge your car's supercaps in 30s and have them feed into the batteries over a longer period of time?

vincnetas 10y ago
I think charging cables would melt from such currents. Or you would need a superconductor charging cables for your supercapacitors. Super everything :)
- geon 10y ago
  Thicker cables? Or would they be too heavy?
  - emeraldd 10y ago
    There will be a physical limit when you attach the cables to the capacitor. At some point, the cable will be larger than the capacitor itself. Also, there are internal components (i.e. the leads attaching to the 'plates') that will become limiting factors. All that to say, there's a physical limit to how much bigger you can make the cables and actually still attach them to the capacitor.
    - geon 10y ago
      At some point, the thermal capacity of the cables will approach that of the brake discs of a normal car. They rarely get hot enough to melt, even though they pretty much absorb the entire braking power. I'd calculate the resistance of copper cables vs car mass and delta v, but I'm too lazy.
- fzzzy 10y ago
  Could use higher voltages instead.
  - achr2 10y ago
    Not for supercaps, most have a breakdown voltage below 5 V.
    - Cerium 10y ago
      That's not important, the batteries also explode if you take them over about 4.2v, you can stack them up to get the desired system voltage.
    - fzzzy 10y ago
      You can just stack supercaps in series to increase the voltage.
msandford 10y ago
> Could this be used to charge your car's supercaps in 30s and have them feed into the batteries over a longer period of time? Think about your question for a minute. Buy a Tesla. It has an 85kWh battery. Now add about 100kWh worth of these supercapacitors because battery charging isn't 100% efficient and neither is discharging supercapacitors. Why would you want to haul around both 85kWh of batteries and 100kWh of supercaps when you can just bring 100kWh of supercaps?
- Cshelton 10y ago
  100kWh in Supercapacitors would have an incredible mass for that much energy. I see Supercaps are being more used for rapid discharges/re-gen periods. I.E. Tesla P100D (0-60 in 2.5sec) punching it would use the supercaps, and then going 100mph and letting regen take ahold, would also use the supercaps. The system would then balance out the power in the supercaps and what can be put into the battery for longer storage. Kind of like a crazy audio system. Has the supercaps that charge up for the bass hits.
  - msandford 10y ago
    Yes, of course. It would be eminently impractical to try and make a vehicle around supercaps at the moment. That's not the point I was trying to make, though. I was trying to point out the systematic error in thinking. You've correctly pointed out that the supercaps are too big and heavy and such. But let's just imagine for a moment that they're made of magic and are 5% of the volume and 5% of the weight of batteries. It's still not a good idea to charge them up to then charge the batteries (from fixed charging stations) because then they're better than the batteries full stop. Throw away the batteries and use them the end. The only way that they make sense is for what you've described, they're electrical buffers to help impedance match "slow" batteries with "fast" motors. But since that wasn't what the parent was asking, I didn't answer that question.

vincnetas 10y ago

I think charging cables would melt from such currents. Or you would need a superconductor charging cables for your supercapacitors. Super everything :)

geon 10y ago
Thicker cables? Or would they be too heavy?
- emeraldd 10y ago
  There will be a physical limit when you attach the cables to the capacitor. At some point, the cable will be larger than the capacitor itself. Also, there are internal components (i.e. the leads attaching to the 'plates') that will become limiting factors. All that to say, there's a physical limit to how much bigger you can make the cables and actually still attach them to the capacitor.
  - geon 10y ago
    At some point, the thermal capacity of the cables will approach that of the brake discs of a normal car. They rarely get hot enough to melt, even though they pretty much absorb the entire braking power. I'd calculate the resistance of copper cables vs car mass and delta v, but I'm too lazy.
fzzzy 10y ago
Could use higher voltages instead.
- achr2 10y ago
  Not for supercaps, most have a breakdown voltage below 5 V.
  - Cerium 10y ago
    That's not important, the batteries also explode if you take them over about 4.2v, you can stack them up to get the desired system voltage.
  - fzzzy 10y ago
    You can just stack supercaps in series to increase the voltage.

msandford 10y ago

> Could this be used to charge your car's supercaps in 30s and have them feed into the batteries over a longer period of time? Think about your question for a minute. Buy a Tesla. It has an 85kWh battery. Now add about 100kWh worth of these supercapacitors because battery charging isn't 100% efficient and neither is discharging supercapacitors. Why would you want to haul around both 85kWh of batteries and 100kWh of supercaps when you can just bring 100kWh of supercaps?

Cshelton 10y ago
100kWh in Supercapacitors would have an incredible mass for that much energy. I see Supercaps are being more used for rapid discharges/re-gen periods. I.E. Tesla P100D (0-60 in 2.5sec) punching it would use the supercaps, and then going 100mph and letting regen take ahold, would also use the supercaps. The system would then balance out the power in the supercaps and what can be put into the battery for longer storage. Kind of like a crazy audio system. Has the supercaps that charge up for the bass hits.
- msandford 10y ago
  Yes, of course. It would be eminently impractical to try and make a vehicle around supercaps at the moment. That's not the point I was trying to make, though. I was trying to point out the systematic error in thinking. You've correctly pointed out that the supercaps are too big and heavy and such. But let's just imagine for a moment that they're made of magic and are 5% of the volume and 5% of the weight of batteries. It's still not a good idea to charge them up to then charge the batteries (from fixed charging stations) because then they're better than the batteries full stop. Throw away the batteries and use them the end. The only way that they make sense is for what you've described, they're electrical buffers to help impedance match "slow" batteries with "fast" motors. But since that wasn't what the parent was asking, I didn't answer that question.