I believe you'll be fine for a month as long as it's not below freezing (which is when the car wants to be plugged in to take care of the high voltage battery). It would certainly help if you had a solar charger, but if you don't have one I wouldn't worry much about it for a month. Alternatively, you can easily unhook the 12V battery in a matter of seconds. All that is required is a 10mm wrench; pop the hood, disconnect the (easily accessed) negative cable from the 12V battery with a 10mm wrench...takes about 30 seconds from start to finish! You won't even lose any of your personalized information like radio settings, etc. when you do this with the Spark EV.
Worst case scenario, if you ever do have a dead 12V battery, you can hook up jumper cables to the 12V battery under the hood and then turn the car on and drive away just like any normal car.
There's a lot of discussion on this topic here:
http://mychevysparkev.com/forum/viewtopic.php?f=7&t=3726&p=6665
This is what the owner's manual states:
Vehicle Storage
Up to Four Weeks
-Plug in the charge cord.
Four Weeks to 12 Months
-Discharge the high voltage battery until two or three bars remain on the battery range
indicator (Battery symbol) on the instrument cluster.
-Do not plug in the charge cord.
-Remove the black negative (−) cable from the 12-volt battery and attach a trickle charger to
the battery terminals or keep the 12-volt battery cables connected and trickle charge from the
underhood remote positive (+) and negative (−) terminals. See Jump Starting on page 10-57 for
the location of these terminals.
If you don't have your paper owner's manual handy, you can reference it online here as well:
2014 Spark EV Owner's Manual
2015 Spark EV Owner's Manual
Bryce
