Mostly the Same, But Tweaked a LittleGasoline cars usually get more fuel efficient over time - though there are exceptions to that, such as when everybody decides that what they really need to carry a couple grocery bags is a big SUV - and electric vehicles should follow the same path. Over time batteries get tweaked and economies of scale bring prices down, so that for a constant amount of dollars we should be able to get bigger and/or better batteries. That's what is happening with the 2013 model of the Chevrolet Volt thanks to GM's battery supplier LG Chem.
In addition, the total storage capacity of the Volt battery has been increased from 16 kWh of energy to 16.5 kWh, and engineers have expanded the state-of-charge window to use 10.8 kWh of the total battery energy – up from 10.3 kWh used in the 2012 model. [...]
Cells with improved chemistry have accumulated 150,000 test miles to date. The tests have revealed less battery degradation, the ability to withstand temperatures as low as -30 degrees Celsius and less impact by energy throughput.
What's nice about this is that we didn't even have to wait for a full model refresh. I'm hoping that this will become the norm with electric cars and plug-in hybrids, giving the latest battery improvements to buyers as soon as they are available rather than wait a few years for a model update.