TomMoloughney said:
My ActiveE for example will only lose about 1% to 2% state of charge if it's parked for a week without use. I expect the i3 to be similar.
For perspective, "standby" losses have the potential to be a very serious issue for an electric car, and they are not alway insignificant. For instance, when it first came out, a Tesla Model S lost battery charge at a rate of 42% to 53% per week of its measured 200 mile range, as observed by Consumer Reports (
http://consumerreports.org/cro/magazine/2013/07/tesla-model-s-review/index.htm):
When it’s left unplugged, we noted a parasitic loss of energy that amounts to 12 to 15 miles of range per day.
During my test drive, the Tesla salesman assured me that the problem has since been fixed, and parasitic loss is now "only" 4 miles of range per day, which works out to a rate of 14% per week.
The seriousness of the potential to be stuck with inadequate range to get to a charging station after a prolonged parking period pales in comparison to the consequences of allowing the battery to completely discharge. Put simply, it will destroy a lithium ion battery pack, and require very expensive replacement.
Ironically, REx owners in the US are more at risk of a total discharge in this scenario than are BEV owners. A BEV owner will be more likely to arrive at the airport with greater than 50% useable state of charge (~57% total SOC), whereas a REx owner driving to an airport that exceeds his electric range will be down to roughly 17% total SOC (assuming BMW allocates the full 13% reserve to the bottom end, plus 4% total SOC [which is the ~5% useable SOC the REx is targeted to maintain]).
What I most want to know is if BMW built in the capability for the car to disconnect the drive battery completely at an emergency level of SOC. If so, the good news is that the self discharge rate is typically less than 2% per month, making battery damage far less likely.