I read a report about Lockheed-Martin signing a contract with a company called EEstore to get exclusive rights to their ultra-capacitor technology in defense and homeland security applications.

I’ve done a bit of looking around, there is a Wiki Page, and if it does 1/10 of what they say it does, it’s impressive tech.

The advantages of Capacitors over batteries are:

• Fast Charging
• Fast Discharging
• Basically never wear out.

The disadvantages are:

• They can lose their stored energy over time, though this can be a long time, as anyone who has been knocked on their ass after opening up a junkyard TV can attest. (This tech is supposed to have self-discharge rate of 0.1% per month)
• Low power density.

This technology looks very impressive:

These units use barium titanate coated with aluminum oxide and glass to achieve a level of capacitance claimed to be much higher than what is currently available in the market. The claimed energy density is 1.0 MJ/kg (existing commercial supercapacitors typically have an energy density of the order of 0.01 MJ/kg and a lithium ion battery has an energy density of 0.54–0.72 MJ/kg).

Maxwell technology has ultracapacitors on the market, and their website has peformance of 3.29 Wh/kg, or about .01MJ/KG.