Capacitors

[DonkeyApple]

Capacitors aren't exactly ideal for powering EVs but what is the reason that we haven't considered using them to bridge charging times?

On paper your EV could have a capacitor and a battery to allow you to stop, bang in a slug of electricity to a capacitor quicker than filling a petrol tank and then drive off with the capacitor discharging into the battery to recharge it as you carry along.

Is it cost, packaging or physics that makes this implausible?

[LukeBrown66]

I know a little about board level caps and have used some big buggers in things like HV power supplies, but they can be quite fragile and arc a lot, maybe modern not so, also weight is an issue I presume? I only know lower level stuff, am sure there must be more refined versions

[gmaz]

To add 60kW in say 5 minutes you would need a charger capable of delivering 720kW, huge cables, and a physically large capacitor. So practicalities and cost prevents it.

[Dave Hedgehog]

https://www.youtube.com/watch?v=KQ2Eo6wl5r0

[DonkeyApple]

Dave Hedgehog said:

https://www.youtube.com/watch?v=KQ2Eo6wl5r0

Thanks. This is a solution which is being considered for other battery tech, such as solid state so as to limit the restrictions caused by their initial very high costs while taking advantage of the complimentary way they will work with old battery tech.

[JonnyVTEC]

You have two batteries essentially…

Capacitors make more sense for a big inrush current like regen braking.

Some batteries are being made with a mix for LFP and nickel cells to allow a similar balance and mix of performance.

[dhutch]

gmaz said:

To add 60kW in say 5 minutes you would need...., huge cables, and a physically large capacitor.

And large capacitors in the charge post!
Or mega voltage. Or break physics.

[saaby93]

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

[DonkeyApple]

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

[arfur]

DonkeyApple said:

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

Or just tow a diesel generator behind you ?

[saaby93]

arfur said:

DonkeyApple said:

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

Or just tow a diesel generator behind you ?

Put the Generator in that space under the bonnet at the front?

[TheDeuce]

saaby93 said:

arfur said:

DonkeyApple said:

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

Or just tow a diesel generator behind you ?

Put the Generator in that space under the bonnet at the front?

If the generators in the car why charge the battery? Just hook it up to the motor direct

[dhutch]

arfur said:

Or just tow a diesel generator behind you ?

A bit like this?

https://youtu.be/scFmBmvVAAs?t=392

[kambites]

DonkeyApple said:

Capacitors aren't exactly ideal for powering EVs but what is the reason that we haven't considered using them to bridge charging times?

EVs already use capacitors as a buffer for battery charging - for regenerative braking. You can't realistically have more than a few hundred Wh though because the energy density is appalling.

[anonymous-user]

DonkeyApple said:

Capacitors aren't exactly ideal for powering EVs but what is the reason that we haven't considered using them to bridge charging times?

On paper your EV could have a capacitor and a battery to allow you to stop, bang in a slug of electricity to a capacitor quicker than filling a petrol tank and then drive off with the capacitor discharging into the battery to recharge it as you carry along.

Is it cost, packaging or physics that makes this implausible?

Current tech capacitive energy storage is a non-start for and volume EV because:

1) The votlage on a capacitor is proportional to its charge. To use "all" the charge in a cap, ie to leverage it's full capacity, that means using "all" the volts, right down to zero volts. That is hard for various complex reasons (which i won't go into here) and requires expensive power conversion. By comparison the voltage vs SoC for a lithium battery is very much flatter, with most of the energy existing between 3.2 and 4.2 volts per cell.

2) The energy density of a conventional capacitor is very poor. A typical practical lithium iron battery has a specific energy density of up to 200Wh/kg and 400Wh/litre. A capacitor sits at about 10 Wh/kg ! This is because the capacitor stores charge, ie electrons are accumulated on condutive surfaces, whereas a chemical battery uses a chemical reaction to convert charge to well, chemistry, ie the electropotential is stored by the materials themselves


So, now you have a hugely costly, difficult to package and develop energy storage system that doesn't actually store much energy and it currently solves a "problem" that actually really isn't a problem. ie the charge rate of a modern high capacity chemical battery is in reality easily good enough for purpose already.

[Tye Green]

arfur said:

DonkeyApple said:

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

Or just tow a diesel generator behind you ?

wind turbine & generator on the roof - the faster you go the .. erm.. faster you go. also, fit solar panels in front of the head lights- drive with full beam.

[TheDeuce]

kambites said:

DonkeyApple said:

Capacitors aren't exactly ideal for powering EVs but what is the reason that we haven't considered using them to bridge charging times?

EVs already use capacitors as a buffer for battery charging - for regenerative braking. You can't realistically have more than a few hundred Wh though because the energy density is appalling.

That and the fact that the next battery technology will be able to accept charge almost as fast a cap anyway - so beyond use as a buffer (as you say) I don't see any reason for capacitor usage in cars to increase.

[Richard-D]

DonkeyApple said:

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

A roof horse seems like a great idea on the face of it. I found the waste products to be undesirable though.

[saaby93]

Richard-D said:

DonkeyApple said:

saaby93 said:

Rather than capacitors what about some form of pumped storage system like the CEGB uses.
You have one tank on the roof and one in the floor
When you charge the car or use regen it pumps water into the roof tank.
When you need more power you flush the top tank through a generator
or better still use it to drive a water wheel connected directly to the transmission

Or a horse, on a treadmill on the roof? For people without an Esso fuel depot in their drawing room, powering an EV by green apples would be ideal?

A roof horse seems like a great idea on the face of it. I found the waste products to be undesirable though.

And the low bridges thread ....

[delta0]

Scalability and cost have held back super capacitors from being feasible at this time. In theory you could charge up very quickly with them and also absorb all the energy from braking no matter how hard. You would probably need to have super capacitors in recharging stations too in order to discharge them quickly into vehicles.