Ultracapacitor with most Wh/kg?

[EG-NRG]

I'm almost building an EV, primarily using 500Wh ultracapacitors.

Highest specific energy density I've seen so far are Nippon, 3-4 Wh/kg, so too heavy

Can anyone suggest where I can find some ultracapacitors with a higher Wh/kg?

[jakobnev]

You can't just wish things into existence EG-NRG.

(And Wh is a unit of energy, not power)

[EG-NRG]

Corrected.

Would like to source a better product, if a better product exists.


Edit: Trawled google, now up to 6 Wh/kg for ultracapacitors and 30 Wh/kg for lithium hybrids

[rmay635703]

Caps do not get much better and are never better than a real battery.

They are great for drag racing ashort distance

[EG-NRG]

I understand the application. Planning to use a block of them for 0-60 and 60-0 (mph) so that power will always be available on demand and buffer regen effectively.

As the caps will cover all peaks in load, this will allow me to significantly downsize the Li battery in my design - improving; weight, safety, costs, environmental etc..

The 6Wh/kg ultracaps mentioned earlier launched back in 2010, not exactly pipe dream tech lol

[lobster]

Hi EG-NRG.

SkelCap 10400 high power ultracapacitor is rated at 10.1 Wh/kg.

See pdf spec sheet on link below. Re type http.

h..p://skeletontech.com/Skeleton-Technologies-SkelCap-Datasheet-120608.pdf

[rmay635703]

Originally Posted by EG-NRG

As the caps will cover all peaks in load, this will allow me to significantly downsize the Li battery in my design - improving; weight, safety, costs, environmental etc..

While I don't disagree that they will significantly improve heat, wear and resistance I do not think they will "cover all peaks in load"

A cap is great (even a very large one) at providing instant power for a few seconds. Off the line it would be amazing and then not so much rather quickly.

Beyond a few seconds there are issues, by design a cap sags in a linear fashion to provide power. This means if you build say a 4ahr cap pack (which is very large indeed) and your goal voltage is 144v you would only have .27 ahr available from the cap bank to buffer the battery before it sags to the point that the battery is providing almost all the power anyway. AKA .27ahr = 10v of sag.

I am uncertain if this is you goal or if you plan on lugging around massive amounts of caps

[EG-NRG]

Originally Posted by rmay635703

Beyond a few seconds there are issues, by design a cap sags in a linear fashion to provide power.

Planning to use a DC-DC converter or (inverter and) transformer, using the top third of the voltage range of the cap bank. I expect the sag to be observed as a drop in the amps and power supplied to the motors.

[serialk11r]

I did an extensive search last year for ultracapacitors, I am fairly sure the better caps aren't commercially available. So far, I believe some Japanese company has claimed that they've made a pretty good lithium doped capacitor, and Subaru has talked about using it, but it's all vaporware.

[GreenHornet]

The Skelcaps are avail in fact I have the price sheet if you guys would like to see :-) They are spendy but you get what you pay for!

There are other companies here in the states who produce these high level caps one in particular is IOXUS out of NY State. They sale them commercially along with there Supercap-Lithium hybrid batteries which is another option. If you guys are interested I can point you in there direction and where to get them.

The caps main function is a support role such as for starting, aux power to radio, lights etc., regen braking, and load leveling.

They are not intended to replace the battery. However done correctly as suggested you could reduce Lithium or whatever battery chemistry pack size. Note you would have less range with this strategy. If you tried to replace the entire battery pack with current supercap energy levels you would be highly disappointed even in an extremely aerodynamic lightweight vehicle. Even at 10 wh/kg the supercaps would not last long you would be hand pushing the car in no time! The capacitor bank would be bulky heavy and cost prohibitive for any DIY guy or auto manufacturer for that matter. As stated above they can and have been used in drag racing and in fact the students from BYU hold a NEDRA world record in there classification. The car is a donated GM EV-1 that runs completely off of Maxwell Ultracaps! Google it and you can read all about it.

Until they commercially develop the Graphene supercaps which will most likely not be in our lifetimes driving on an ultracap bank probably will not happen. Unless you just want to go around the block :-)

The strategy for ultracaps would be for regen braking and start stop tech in BEV or in a hybrid design. If setup in this fashion they will help extend battery life. A company in Japan produced an ultracap-lead acid hybrid which they named the ULTRABATTERY and it was able to extend the lead acid battery life by a nice fraction. Similar companies have done it with other battery chemistry's such as Lithium Ion and Iron. ultracap pricing has been coming down faster than battery pricing however its still spendy.

Good Luck,

GreenHornet