1pm 4-20 Deposit Email. Get It Yet?

Yes, the amount of power consumed would be the same in all 3 cases (120/240/480V) charging, however, the 120/240 is single phase, and the 480 would be 3 phase, which is better for the "power factor" and balance of the grid (since the generated power from all utilities is 3 phase). The 3 phase, 480V, 100AMP (50KW output) charger is rumored to cost upwards of $65K, and will only be deployed in Leaf heavy areas, I imagine, and for "fleets" for companies. Eventually they plan to have "EV public refueling" stations, they will use this fast charge technology, however, 480V, 3 phase is only available commercialy for the most part.

The onboard Leaf charger is rated at 3.3KW max, so if you do some math (divide the maximum power by voltage), you can get some idea of amperage at the voltages as well. The .80 saftey factor is a derating, so the circuit breakers don't trip due to overheating, and is a commonly used maximum load msize when electricians size circuits.

120V * 15AMP circuit * .80 derating = 1440 watts, or 1.44KW
120V * 20AMP circuit * .80 derating = 1920 watts, or 1.92KW

240V * 20AMP circuit * .80 derating = 3840 watts, or 3.84KW

so you can see the max circuit you can use with the onboard Leaf charger is the 240V/20AMP circuit, and the draw on that will not exceed the 3.3KW #

If you divide the Leafs 24KW pack by each KW rating, you get the # of hours to charge a fully depleted pack.

24KW / 1.44 KWh = 16.66 hours
24KW / 1.92 KWh = 12.50 hours
24KW / 3.84 KWh = 6.25 hours

This is why they want everyone to install the 240V charger.
Of course the Leaf pack won't be fully depeleted most of the time, and there are also some charging loss's, so these numbers are approximate.

Look at the 480V math:

480V * 100A * .80 derating = 38.4KW

24KW / 38.4KWh = .625 hours or 37 minutes. Nissan is quoting 26/27 minutes on the web pages I have seen

 

Nice summary, Mitch. My only comment would be that higher charge rates would tend to be less efficient than lower charge rates due to resistance losses at higher currents.

I also notice that the Leaf FAQ suggests a 240V/20A circuit but a 240V/40A circuit would be better - I wonder why given than the 20A circuit can easily handle a 3.3 kW draw. Perhaps it's just to reduce resistance losses?

They are claiming it takes 26 minutes to quick-charge a battery from empty to 80%. Using your 38.4 kW quick-charge rate that would indicate that a 80% charge is 16.64 kWh and a 100% charge is 20.8 kWh. Which makes sense as you don't want to fully charge/discharge a battery pack if you want it to last.

So assuming that 20.8 kWh is a full charge, the Leaf then can be calculated to travel 4.8 miles / kWh on the LA4 city cycle.

 

Mitch, Drees -

Excellent stuff - thanks much for posting the math.

> The 3 phase, 480V, 100AMP (50KW output) charger is rumored to cost upwards of $65K<

The part that I don't fully understand is that I thought the "charger" was in the car, and the "charging station" was little more then a surge protector and a power tap - if so - why such a high price - it just thicker wires.

-Lake

 

So how many extra miles would you get with all the regen braking since it is mostly stop and go city cycle?

 

There's no way to calculate that without having data loggers on the car monitoring power flowing in/out of the battery pack during an actual LA4 test cycle.

 

Yes, there is the 3.3 kW charger built in to the car which converts AC power to DC power. This is for the 120-240V 15-20A home charging and has a plug which complies with the [ame="http://en.wikipedia.org/wiki/SAE_J1772"]SAE J1772[/ame] standard. The charging station does have a small amount of smarts as it must communicate with the car before supplying power.

The Level 3 quick charger 480V, 80A) very likely converts grid AC power to DC power. That's the primary reason the quick charger costs tens of thousands of dollars compared to the couple thousand that the standard charger costs.

The Leaf has a different charging port for quick charging when using a Level 3 charger.

The SAE J1772 is "only" good for 240V at up to 80A. It would take about an hour to charge a leaf using that type of power. But It seems that most initial implementations will only be good for up to 30-40A or so.

 

The high cost is because 480V 3 phrase power is not available to residential users. A 480V 3 phrase transformer is requires to be installed the nearest transmission line and run a special line to your house.

 

The high cost of a Level 3 charger has nothing to do with the fact that it's nearly impossible to get at your house. You could have the 480V 3-phase power readily accessible but that won't change the cost of the charger.

It has everything to do with the fact that it's not cheap to build a charger than can handle that power safely and convert that power to something that the car can use (which is very likely high-voltage DC!)