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      07-31-2014, 10:45 PM   #13
jadnashuanh
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Drives: 535iGT x-drive; i3 BEV
Join Date: May 2010
Location: USA

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People don't always realize that the actual charging circuits are built INTO the car, the EVSE is basically a fancy on/off switch with a dedicated extension cord attached. The fact that it may have more power than the car can use is essentially the same thing when you plug your phone charger into a socket that COULD supply 15A, when it only draws one amp to recharge the phone.

Now, a DC fast charger is a bit different story, but there's still a limit on how much the vehicle can absorb, so it can still limit the rate at which it goes into the batteries. The difference is, you're not using the AC-DC converter in the car, which is the limiting factor when using AC as the input. TO get the maximum rate DC fast charge on the i3, you need a unit capable of 50Kwhr output, and again, they are not all created equal, but the i3 will not draw more current with any connection than the computer is programmed to allow.

Bigger in vehicle converter would be more expensive, bigger, produce more heat, and as with anything, there are compromises. Personally, I think BMW got it about right, but somewhat question their decision to use a lower-power DC fast charger as their lower-cost option. It won't be able to recharge the vehicle in the 30-minute timeframe of a 'full size' one, just like what happens when you use a lower powered EVSE.
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