Per this site
, for the LEAF's 24kWh Li-ion battery:
Charging time: 16 hours at a 100V outlet, 8 hours at a 200V outlet
Fast-charging time: 30 minutes 0-80%
The sparky in the Nissan video looked to be pulling in #6 wire, but I'd imagine they have multiple options, depending on how much power is available, on down to a simple 15A plug. 24kWh would only take 2 hours if you could charge at 50A 240V. Now, one thing to note is that Li-Ion charge rapidly to 80%, but very slowly after that. They're also extremely sensitive to heat. If they get too warm during charge (or discharge), protective electronics have to STOP!! or risk causing thermal runaway and the battery turning into a big fireball. I've not heard of any particular issues with heat or cold beyond this, but much-abused cell phone Li-Ions only seem to last 2 years, so I'm wondering how Nissan thinks these will last 10 under similar abuse.
IIRC, the batteries last much longer (years/degradation-wise) if you don't discharge them below 30% or charge above 80%. Chevy Volt only uses about half the capacity of their battery for this reason- if Nissan does the same, then that 24kWh battery is really only ever going to need about 12kWh of charge, and you can cut estimated charging times in half.