New Gizmo Type - Lithium Ion Capacitor
 

A Lithium Ion Capacitor is cross between a battery and a capacitor.
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"lithium-ion capacitors have a higher power density as compared to batteries"

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"Lithium-ion capacitors are quite suitable for applications which require a high energy density, high power densities and excellent durability. Since they combine high energy density with high power density, there is no need for additional electrical storage devices in various kinds of applications, resulting in reduced cost of ownership."

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Lithium-ion capacitor - Wikipedia, the free encyclopedia

Real devices

Cylinder Type Lithium Ion Capacitors | TAIYO YUDEN CO., LTD.

you can buy

Lithium Ion Super Capacitors - Taiyo Yuden | Mouser

<Ponder Spending Money Now>

Technical info

http://www.mouser.com/pdfdocs/LICpre...ge20131110.PDF

So, that appears to be an evolution from the high power, but lower voltage Lithium Titanate batteries.
This should make a lightweight high-power hybrid brake power regaining system possible.

My Insights 27 kg NiMH battery can only absorb about 10 kW under braking. That feels like coasting, especially at higher speeds. Too often I need to brake harder, like 'normal', wasting the momentum into heat and brake dust.

Yet, as a battery it falls short a bit as 14 Wh per kilo is way less than the 100-265 Wh/kg Wikipedia attributes to regular Li-Ion batteries.
A mixed pack though could be a winner.

After reading some more technical info its not the capacitor battery hybrid I was hoping for. It still largely behaves like a capacitor, it just has higher energy density and you don't want to discharge it all the way(from what I can tell so far).

I wonder what the charge-discharge hysteresis would be of these LIC's.
That may well be very low, even less than LiFePO4 cells.
Low hysteresis means hardly any heat buildup on charge/discharge, so no need to ventilate them etc. If so, these cells could reduce the heat buildup in a mixed pack by dealing with the short term high charge-discharge peaks.

Bet they won't come cheap...

They are saying there is very low heat with this technology. The 270F cap is $57 in small quantities but I don't think its high current.