Charging the MINI E

Deutsche Version

The charging device of the MINI E has some specific feature. Normally an electric car needs a special device called "on-board-charger" to alter the incomming AC to battery suitable DC and adapt the current to the charging characteristiks of the battery.
MINI Es electric drivetrain supplied by AC Propulsion does not need a special on-board-charger, because this functionality is integrated to the power electronics and the components of the drivetrain. AC Propulsion calls it the "reductive charger".

Electric drivetrain of MINI E. (source: gm-volt.com)

Using the components of the drivetrain limits the charging input source to a single phase and a maximum voltage of 240V. But the current is allowed to be fantastic 80amps leading to a maximum charging rate of 18kW.
In the MINI E the maximum setting is reduced to 50amps allowing a charging rate of 12kW at 240V.
But of course, this setting has demanding requirements to the electric infrastructure and for the private user in Germany it is useless.
The second setting 32A is the standard setting for charging at the wallbox or a public charging station. At 32A/230V it delivers a charging rate of 7,3kW.
The 12A setting is for charging at a domestic wall socket and delivers 2,8kW at 230V.

Using the components of the electric drivetrain for charging the battery may be both a technical challenge in detail and may be patented by AC Propulsion, so all other electric vehicles not equipped with a drivetrain from AC Propulsion need a conventional separate on-board charger. 

An example for a typical on board charger is this device from the swiss company BRUSA.

It has a charging rate of max. 3.3kW which is sufficient for charging at a domestic wall socket at 12A/230V. It is a modular system, so you can combine two of them to get a charging rate of 6,6kW (this would fit to the 32amp charging stations)...

Two chargers onboard the Audi A1 e-tron (source: autobild.de)

 ...or even three to get 9,9kW.

 

Three chargers onboard the Rolls Royce Phantom 102EX (source: bimmertoday.de)

The installation of several of these chargers is an issue of cost, packaging space and weight.

Interestingly, for example the combination of two chargers can handle either a single phase input of 32amp/240V or a two phase input up to16amp/240V for each phase. This may have advantages for the electrical infrastructure.

Additionally the combination of an "on-board"-car module and an "off-board"-wallbox module is possible. This offers the possibility to give the car a basic charging rate of 3,3kW for occasional charging at domestic wall sockets (plus saving weight and space in the car) and a boosted charge at the own wallbox. However, boosted charging at public charging stations won't be possible as long the charging station is not equipped with an "off-board"-charging module as well.  

The development of the chargers continues and aims at a more compact style with an increase of the charging rate. The matters of smart grid capability and data transfer via the powerline could be realized by the on-board-chargers, too. An example could be the EDcharge of the EDAG company.

Compact 11kW charger with communications interface.

So the charging rate of the MINI Es, Teslas and other cars equipped with an AC Propulsion drivetrain is mostly limited by the electric infrastructure, whereas the charging rate of other electric cars is mostly limited by the built-in charger.