How Many Amps at 120V

The "nominal" value is 12A.

 

Actually it's about 1 amp higher than what's in the graph (.94 amps to be accurate) as compared to my Kill A Watt

 

The correct number is 15 since you need to de-rate it by 20%.

 

huh?

 

Any time a circuit might be energized for more than 2 hours, it's amp rating is decreased by 20%. If you need 12 amps, the circuit should be rated for 15. Since this is a pretty standard circuit rating, I do not think it is a coincidence that the charger needs 12 amps.

 

3 hours, not 2 (see NEC article 100). Not that it matters in this case.

 

Ah. now I see the confusion, I think the question was how much does the EVSE draw and the answer is about 12 amps, not what the circuit should be rated at.

 

Yes...the 120V EVSE draws 12A nominally, meaning it has to be plugged into a circuit rated for not less than 15A.

 

and now I see why the circuit question was raised, duh!

 

The current draw is controlled by the Primes on-board charger. With the 120volt EVSE, the maximum draw is 12 amps. In the "Vehicle Settings" (on the MID), you can lower the maximum charging current to 8 amps. Decreasing charging current to 8 amps could be useful should you need to connect to an extension cord, or to an old or sub-standard electrical system (old home or hunting camp). Reducing the current will lengthen the charging time, but will decrease the voltage drop over the length of the extension cord (or sub-standard home wiring). Decreasing this voltage drop (and the resulting "heat") will reduce the chance of fire, and improve power efficiency of the charge cycle.

 

It could improve or reduce the charging efficiency.

On the Volt and Spark EV the car has a couple of hundred Watts parasitic load (running computers, fans, cooling system etc), So at lower charge rates (It defaults to 8Amps) the efficiency is lower.

Overall I measured about 83% efficiency energy in to battery out on the Spark EV using level 2 (240V) with about 78% with level 1 (120V 12A).

The Prime has a simpler battery cooling system that probably takes less power so that may make it better at the lower charging rate.

kevin

 

So today I ate lunch using an L2, EVSE running on 211 VAC (commercial power is three phase versus split-phase, 240 VAC at home.) During the charge session, the car drew 16A @210 ~= 3.38 kW. The total charge was 2.32 kWh input to the car and ~8.4 miles EV on the car internal meter. Here is the session from the EVSE:

So (32 min + 10 min) / 60 = 0.7 hr; 0.7 hr * 3.31 = 2.317 kWh . . . don't 'cha love maths!

Now I have a split, 30A 120 VAC circuit at home and two EVSE:

• 8A - Prius Prime
• 12A - BMW i3-REx due to (I**2)*R, the end voltage is typically 110 VAC, ~1.3 kWh
  • after 4 hours, ~5.2 kWh or +18.9 mi, best case added to the ~8 miles on the meter, ~26 miles (*)

I need to run a quick errand about 7-8 miles away where there is another L2 charger. I should be able to do it all EV. Well time to scamper down to the store.

Bob Wilson

* - most battery management systems taper the charge towards the end so you don't get the full charge rate. This is done to avoid overheating the battery.

 

I think the question was power draw, not the rating of the breaker. However, it looks like the designer of the charger properly derated its current draw to allow installation on a 15 amp circuit. But, i would be money that the recommended disconnect size is 20 amps ...

 

OM, Page 122:

Power sources
Connect to an AC 120 V outlet (NEMA 5-15R) with a Ground-Fault
Circuit-Interrupter (GFCI) and a circuit breaker. Use of a 15A individual
circuit is strongly recommended to ensure charging cable will
operate properly.

 

At least I am lucky at love ...

As soon as I posted that I looked up the cable and saw the error of my ways. However, notice that GFCI is recommended on a dedicated circuit. So most existing garage circuits wouldn't work (garages typically already contain a beer fridge/freezer/air compressor).

I wonder how dirty the wave form that back feeds into the circuit is? The power pollution issue is sure to raise its head when charging stations become more common.

 

A GFI is usually required in a garage or workshop. The height above the floor is sometimes taken into account. I would always recommend bringing a 30 amp 110/230 volt circuit to the garage to a subpanel. The difference in cost is nominal and you have a lot of flexibility in your output circuiting. The wave form might affect the charger, but the battery would act as a filter ahead of the car.