Is there a supercapacitor sub-forum?

[gromike]

Last night I got sucked into this new for me world of electrical energy storage -- supercapacitors!
Not something new, I found out.
One popular application is the surge powering of woofers in a car. I guess people like the feeling of rattling the fillings out of their teeth.
Go figure!
Anyways, it got me thinking. It doesn't seem like anybody is doing a battery/capacitor storage system for an ebike. It would to be something that would really work well in a ebike that has regeneration integrated into it's system.
So hence -- a supercapacitor sub-forum? Hybrid energy storage systems?
Where are we to have this discussion?

 

[A-DamW]

Yea, not really new, I've been starting my Cummins diesel pickup with a 6 pack of Maxwell 3000f supercaps since 2013, works a treat.
I'll probably never have to buy lead acid batteries ever again for vehicle starting.

This is decent thread on the various considerations of supercap applications;
The case for using Supercapacitors with Lithium-Ion batteries in EV's

 

[neptronix]

ebikes are physically constrained for battery storage and supercaps contain about 1/25th of the energy density, so you're just hurting yourself financially and range wise by using them due to the massive space they use.

You can get way more power than you need out of lithium by choosing the right cell. There's no need for supercaps in a vehicle.

You've been able to start a car with a 3lbs high performance lithium battery 10 years ago. Lithium has got 2-3x more powerful since then:

 

[gromike]

This is decent thread on the various considerations of supercap applications;
The case for using Supercapacitors with Lithium-Ion batteries in EV's

I quickly pursued your linked thread and it came to me that the easiest application of a supercap in an ebike would be a circuit to eliminate voltage sag of the battery during acceleration. I'll get back to the thread -- but it's E.O.D. para mi.

 

[neptronix]

Or you could just buy a high rated lithium, which would be a LOT cheaper and a LOT smaller.

5AH packs with 150C ratings won't flinch at a 100A load; their internal resistance is a few % of what a typical high energy cell would be. You'll be hard pressed to even measure voltage drop at loads lower than that ( not enough digits on the voltmeter )

How fast of a vehicle are you planning to build? drag vehicles won't even use them as a primary battery because way they're too heavy; despite the great power density, their energy density ls laughable.

Because their energy density is laughable, the amount you could stuff on a bike will only help a very weak lithium battery for a very short period of time. Those supercaps will be dead weight during a hill climb.

 

[neptronix]

Example: i used to run a 2C draw on 20C lipo, i'd see .2v of voltage drop at full throttle.
..that was with the lithium technology of a decade ago..

 

[gromike]

With its own Moore's Law capacitor tech is also quickly evolving. It's not about replacing the battery, it's about supplementing it. An instantaneous flywheel, so to speak. This, I believe, is already being done in ev cars and motorcycles, just not on ebikes at the moment.
Yeah, supercaps are big, but getting smaller and cheaper by the day, and they don't weigh all that much.
A hybrid energy system seems to be the way to go on an ebike with a robust regen drivetrain.

 

[harrisonpatm]

 

[ElectroXa]

Hello,
there are now a few exemples of commercially available e-bikes with only supercaps as energy storage, like Pi-pop, ostrichoo or a hybrid solution anod (with a 54Wh Li-ion battery + the supercaps)

but the problem is the limited storage, only for starting or a small hill, and the drag when the caps are charging when on a flat road or downhills, and the limited range

it's useful in cities when you brake frequently at traffic signs, then reaccelerate, or in cities with small hills, to help avoiding arriving at work sweating

 

[gromike]

I am more thinking about a hybrid energy storage system where the capacitor bank handles the high current transient loads, while the battery provides the electrical capacity. With this, the battery design can shifted from power cells to those with a high capacity.
Seems like it could be a win/win kind of thing.
Now I have to find the mule to do this experiment on. The twenty-year-old MTB's I have been playing around with ain't that animal. Maybe one of those older Rad direct drive cargo bikes would fit the bill.

 

[Chalo]

Anyways, it got me thinking. It doesn't seem like anybody is doing a battery/capacitor storage system for an ebike.

Because it's a bad idea. The energy density is so low, you can achieve much better benefits by adding a little bit more battery.

Electrically, a capacitor is just a spring. It provides neither constant force (voltage) through its operating range, nor a useful amount of energy. Capacitors are great for rectifying and smoothing power, but they suck at storing it. We already use them for what they are good at.

 

[gromike]

I think the technology of capacitors has sufficiently evolved as far as energy storage, and prices have become low enough, for someone like me who lives on technology's lagging edge can freely experiment with them.
My idea is an an electrical flywheel to supplement a battery.
Anyone know where I can find a Radwagon 1 cheap?

 

[gromike]

Let the fun begin! I just purchased, from Battery Clearing House, 180 38F super capacitors for $90 delivered.

Product image	Description	Quantity	Price
2	38F Super Capacitors - 2.7V - Set in Server Card Units (6 caps per card)Lot of 90 - 38F Super Capacitors - 2.7V - Set in 15 Server Card Units (6 caps per card)

It will take 20 of them to make one series string for a 48v system, and I will need multiples of these series strings in parallel to get higher fareds for more stored power -- well, I just hope they ain't too big.

I'll get the donor bike after I build the bank (trying to be a bit smarter this time.)

 

[neptronix]

It will take 20 of them to make one series string for a 48v system, and I will need multiples of these series strings in parallel to get higher fareds for more stored power -- well, I just hope they ain't too big.

How many amp-hours will that be? any spec listed?

They're going to be approx 20 times bigger than lithium per amp hour ( probably worse since you didn't buy name brand ones ), so i suggest also ordering a trailer to carry it.

 

[neptronix]

I think the technology of capacitors has sufficiently evolved as far as energy storage, and prices have become low enough, for someone like me who lives on technology's lagging edge can freely experiment with them.

Last time i checked, maxwells ( expensive, name brand ) top out at ~15whrs/kg. That's 5 times heavier/bigger than lead acid batteries.
What kind of whrs/kg are you seeing on modern supercapacitors that i missed?

 

[BlueSwordM]

15Wh/kg with lithium-ion supercapacitors.

 

[Gruesome]

I also don't see the math (or physics) working out with this. Say you put 18 of them in series, and you use the voltage range from 2.7V down to 2.0V, which is 48.6V down to 36V. For each $90 batch of 90 capacitors you can build 5 strings of 18 caps. Each string is a 48.6V 2.11F (=38/18) capacitor. From the array of 5 parallel strings you can withdraw 18*0.7V*38/18F*5=133As between 48.6V and 36V. At an average voltage of 18*2.35V that is ~5,600Ws or 1.56Wh. That $57.60 per Wh, $57,600 per kWh. Really super expensive.

My understanding (could be wrong) is that supercapacitors make sense if you need a ton (say, 1000 Ampere) of current from a small device, and don't want to keep blowing up and changing out Li-ion cells all the time.

 

[Chalo]

I lived through the hype, obvious scam becoming obvious, and overdue failure of EEStor, an Austin area company/investment swindle that unfolded in the mid to late 2000s. They promised superduper capacitors with battery-like energy density. They delivered... disappointment. And anger, I hope, from investors who realized they never had diddly.

When I moved back to Austin from Seattle at the beginning of '07, I only had two companies on my short list of easy prospects: EEStor and Fallbrook (NuVinci). They were both in far flung burbs, so I waited for the long promised light rail line to come active. It was years late, so that probably saved me from getting into something I would later regard as a waste of time.

Even if EEStor had actually fulfilled their technical promises, it would not be an easy thing to harness a superduper capacitor in parallel with a battery.

The voltage in a capacitor doesn't have a plateau like a battery. It falls continuously on discharge. It can have a jillion watt-hours on tap from max voltage to zero, but all you get to harvest is the margin between your battery's full and empty voltages, unless you use lossy buck/boost conversion to bring its capacity to bear.

To be frank, if you only have superduper caps in parallel with your battery to stiffen voltage sag, you'll get a miniscule fraction of its already lame energy density. The voltage gradient you get to reap is that between the sagged battery voltage by itself, and whatever propping up the superduper cap can support. Everything above and below that voltage in the cap's repertory is wasted, inaccessible.

In the absence of magic, like room temperature superconductors, I don't think the super duperest possible capacitors will ever exceed the energy storage potential of lead or nicad batteries. And we've already left those in the dust except for applications where energy density doesn't matter.

 

[gromike]

These capacitors are from a server backup, probably for momentary drops. I assume the technology evolved, and now they are in the waste stream. It's $90 for 180 38F caps. If I build 8 strings at 48v (nominal) I figure 17,510w. That's for one second! What I wrote down is at 100a at 48v it will run for 4.5 seconds.
The goal is to have this coupled with a robust, integrated regen motor, and do a balance between the battery and the almost instantaneous charge/discharge cycle of the capacitor bank.
They do it in cars. It will be fun to try to do it in ebikes.

 

[BlueSwordM]

These capacitors are from a server backup, probably for momentary drops. I assume the technology evolved, and now they are in the waste stream. It's $90 for 180 38F caps. If I build 8 strings at 48v (nominal) I figure 17,510w. That's for one second! What I wrote down is at 100a at 48v it will run for 4.5 seconds.
The goal is to have this coupled with a robust, integrated regen motor, and do a balance between the battery and the almost instantaneous charge/discharge cycle of the capacitor bank.
They do it in cars. It will be fun to try to do it in ebikes.

Nice project but last I checked, they don't do it in cars. They all shove power into the battery.

Last I checked, the Model S Plaid has 200kW regen and the mighty 2025 Porsche Taycan has 400kW battery regen.
It's usually better to just increase battery power density or to use a secondary extremely high power density pack.

Anyway, if you want a motor for very high power regen, I recommend using a geared hub motor. DD motors are fine, but they're far from the best if you want powerful regen as the motor usually isn't spinning fast enough.

 

[neptronix]

They do it in cars. It will be fun to try to do it in ebikes.

There's no car that uses supercapacitors. They all use lithium batteries because of the ultra poor energy density of supercaps.
There's no use for supercaps in an EV because the lithium battery of today is totally capable of very strong charge and discharge.

Anyway, if you want a motor for very high power regen, I recommend using a geared hub motor. DD motors are fine, but they're far from the best if you want powerful regen as the motor usually isn't spinning fast enough.

I don't agree with this, certain ebike controllers can have powerful regen down to 0rpm, for example the VESC. This is not the DD's fault.

Geared motors lack the heat shedding capability to handle a lot of forward power & then also regen on top. Both create heat. DDs have tons of thermal mass and are also WAY better at heat shedding.

 

[gromike]

There's no car that uses supercapacitors. They all use lithium batteries because of the ultra poor energy density of supercaps.
There's no use for supercaps in an EV because the lithium battery of today is totally capable of very strong charge and discharge.

What I have read in reputable sources is that supercaps have been used in hybrid cars for regen.

 

[neptronix]

What I have read in reputable sources is that supercaps have been used in hybrid cars for regen.

Name a model that does.

 

[gromike]

Supercapacitors still cannot supply the power output of a lithium-ion battery of equal size and weight. For now, this rules them out as an electric car option, but they can still find a place in hybrid vehicles as Lamborghini has proven with the Lamborghini Sián FKP 37.Dec 12, 2019

 

[neptronix]

Yeah.. limited run supercar with zero economic restrictions on the design.. even has titanium valves in the engine.

Ok, you found one