Super Capacitors

[LockH]

ES Bible "Search found 100 matches: +"super capacitor""... again, on DIY electric bikes:

The 200W+ AA Battery Electric Bicycle
("A 200W+ electric bicycle powered by a bank of regulated super capacitors that are charged by 10 AA batteries."):
https://hackaday.io/project/21058-the-200w-aa-battery-electric-bicycle

Author notes:

Description
Following on from my previous project (https://hackaday.io/project/15327-a-super-capacitor-pulsed-power-24v-dc-supply), I have found a electric bicycle conversion kit (24V/250W) on eBay that is perfect for the application of the "24V" super capacitor bank.

For the size of the capacitor bank (4375 Joules) and the power rating of the motor (250W), I can calculate a run time of 17.5 seconds at full power. Conversely, with a charging current of 0.5A, I can calculate a charge time of 18.2 minutes. So practically, I can expect to have at least 12 seconds on and 18 minutes off (1:90 ratio).

Ultimately, this electric bicycle is just a regular bicycle (albeit heavier) that has a 12 second boost for tough hills. Truly an exercise in (entertaining) madness.

:lol:

 

[maydaverave]

Just get a couple of these bad boys in series.
https://www.amazon.com/gp/aw/d/B00PU71REG/ref=pd_aw_sim_sbs_328_2?ie=UTF8&psc=1&refRID=WFDE28QZBDXVN6J27GWF&dpPl=1&dpID=41kSVoNtcyL&th=1

 

[flat tire]

Exercise in madness indeed.

 

[Sunder]

Send me to the lunatic asylum then...

I'm dreaming about a pack that could deliver 30kw for 10 seconds or so - the time required to do a quarter mile. To do that, I'd need 30000wh /60 minutes /60 seconds * 10 seconds, or about 83wh

Looking at these:
http://www.maxwell.com/images/documents/K2Series_DS_1015370_5_20141104.pdf

I'd need 55 of them to make up the voltage of my motorcycle

55 x 1.52wh (The BCAP1500) would be 83.6wh - perfect.

Now... Where to stash them?

 

[Punx0r]

Hold on just there

Capacitors are not batteries and connecting them in series reduces the capacitance. 55-off 1500 Farad caps in series gives only 27F.

55 x 2.5V = 138V

Stored energy (Joules) = 0.5CV = 0.5 x 27 x 138 = 1863J

1J = 1 watt-second

1863J / 3600 = 0.5Wh

And that's assuming you drain the cap bank completely to 0V, which you won't be able to do with any normal motor controller, so actual usable energy will be far lower.

Bear in mind that's 15.4kg of capacitors.

 

[Hillhater]

.....
Bear in mind that's 15.4kg of capacitors.

......and each one is the size of a Beer can !

 

[flat tire]

quarter mile

The supercaps could do it but you would need a lossy and expensive controller to convert the extremely high amperage <3 volts to higher voltage for the motor drive from a big parallel bank of those caps. In reality the best way to build a 30KW electric drag bike is lipo, no arguments.

 

[liveforphysics]

Send me to the lunatic asylum then...

I'm dreaming about a pack that could deliver 30kw for 10 seconds or so - the time required to do a quarter mile. To do that, I'd need 30000wh /60 minutes /60 seconds * 10 seconds, or about 83wh

Looking at these:
http://www.maxwell.com/images/documents/K2Series_DS_1015370_5_20141104.pdf

I'd need 55 of them to make up the voltage of my motorcycle

55 x 1.52wh (The BCAP1500) would be 83.6wh - perfect.

Now... Where to stash them?

Today's available super caps are lower power density and 1-10th to 1-100th the energy density. So your dragster would be heavier and weaker and only travel a quarter mile VS using some high C-rate pouches.

 

[Hillhater]

So, what do we think the chances are of this guy succeeding in his 6 sec quest ?
http://fast-charge.org
http://ev1000.blogspot.com.au

And this is the power source !.....

 

[Sunder]

Ah Damn. Back to LTO then.

High Power SCiB? 1800w per cell x 55 cells? 99kw:

http://www.scib.jp/en/product/cell.htm

But as I said before, this is a pipe dream, I'm not actually going to do it... Yet.

 

[amberwolf]

FWIW, if you're curious about the details, supercaps, ultracaps, etc, have been discussed as batteries and the maths and other stuff worked out in various other threads (using those and similar keywords in their titles or first posts, so easily found in a search).

Using them as a current-boost to crappy batteries might be useful on a high-power setup, if you happen to be limited to only those crappy batteries, and also happen to have the caps laying around already, and don't mind the weight and volume penalties.

But if you have the money to spend on the caps you'd be better off to spend it on better batteries.

 

[Sunder]

The idea came because I had a 40ah 43S LiFePo4 battery still with good capacity, but horrible internal resistance. I'm talking easily 40v sag @ 90amps.

I have "stiffened them up" with a small (16Ah) LiPo pack which reduced sag to under 10v at 120a+ but after 6 months of near daily use even those are getting a bit more saggy. (Nothing like the original LiFePo4s though)

I am really not going to do anything about it now, but before the supercaps turned up, I was thinking of running down the LiPo and trying out the 2.9ah SciBs. All i want it to do is buffer the energy for those short sharp hills. Even at 110km/h, I generally don't use more than 50-60 amps. (On the flat it's about 8kw to do 110km/h)

It's just a bit of fun dreaming for now, but give it a year, another got summer, and I might look more seriously at it.

 

[Punx0r]

The datasheet for those Maxwell Ultracaps shows a worringly short service life at max. operating temp (65°): 1500hrs (2 months).

65°C is hot, but not that hot. Plenty of places in the world a compartment in a vehicle could be 50°C+ just from ambient heating. I'd like to see a chart showing the service life reduction from 20°C to the 65°C figure to be sure.

 

[liveforphysics]

So, what do we think the chances are of this guy succeeding in his 6 sec quest ?
http://fast-charge.org
http://ev1000.blogspot.com.au

And this is the power source !.....

His odds of a 6sec pass are great if he uses the right hobby pouch, using caps it would be that much harder if not impossible.