As cheap as lead acid batteries, perhaps cheaper. Thousands of charge/discharge cycles vs. 500-1,000 for lead acid batteries. Demonstration batteries have experienced 5,000 cycles with no decrease in performance. The company expects >20,000 cycles.

More cycles means more years use before replacement. (I’m currently getting 5-8 years from lead acid batteries with my off the grid system. 5k cycles would mean 25-40 years. 20k cycles boggles the mind.)

Can be 100% discharged without damage. Lead acid batteries are normally limited to an 80% discharge. That means one would have to purchase many fewer amp hours of batteries to get the same performance.

High tolerance to battery mismatch. People could add additional batteries as funds allow. Can’t do that with lead acid (performance will drop to that of the weakest battery).

No self discharge or problems in high heat conditions.

Smaller and lighter than lead acid. Easier/cheaper to ship.

100% recyclable.

http://www.aquionenergy.com/sites/default/files/user_files/news-press/2011_esa_aquion_whitacre.pdf

Apparently the battery has been tested by multiple independent labs and has passed their tests.

The company has received $30 million in initial financing. They are currently deciding where to build their first factory and expect to be shipping product in 2013.

Let’s keep our fingers crossed for them….

People using these stand alone systems are pretty much limited to lead acid batteries which have to be replaced every few years. We need a push to get batteries or ultracapacitors with much longer lifespan into people’s hands at an affordable price.