How many EVs does it take to trip a circuit?

[kiastormtrooper]

A resident at my condo recently bought a Leaf, and, I assume, has been tripping the circuit breaker when we charge our cars at the same time. I've read a couple sites that say that an EV should have a dedicated circuit to charge, but none of them explain how many EVs a circuit can handle. A two EV maximum sounds incredibly low.

 

[JejuSoul]

This is a question I intend to ask the company tomorrow.
I currently have a 32A charger on its own dedicated 50A circuit.

The charger has the ability to charge 3 cars either concurrently or sequentially. (obviously depending on the circuit)
I want to get a second EV and use the same charger, preferably concurrently.
To what extent does the circuit need to be upgraded?

 

[notfred]

I presume that the original poster is talking about the Level 1 EVSE cable that comes with the car and is located in the US or Canada.

The Level 1 EVSE will tell the car to draw 12 Amps. A standard circuit for plugs has a 15 Amp breaker, so 2 cars charging at the same time will trip the breaker.

There may be different circuits for different outlets in the condo parking, you will have to check

 

[kiastormtrooper]

Yes, I was referring to the level 1 trickle charger that came with the Soul. So, by notfred's explanation, I just need to add the amps together? So jejusoul can charge 4 EVs on his 50A circuit? If it's not obvious already, I have very little understanding of electrical systems.

 

[JejuSoul]

..., by notfred's explanation, I just need to add the amps together? So jejusoul can charge 4 EVs on his 50A circuit?

Two cars at the same time - add the amps together, yes.
My charger is 32A, so two cars would be 64A which the circuit can't do.

Possible solutions to this problem
1/ Charge the cars one after the other.
2/ Charge the cars together. But at a lower current.
3/ Find or add a different circuit.
4/ Upgrade the existing circuit.

Am lucky because the boss of the company that makes my charger is in town for the EV show and he is going to give me advice on the best solution in my specific situation. Will update this when I know.

 

[notfred]

One of the other things is that in North America the electrical code says that for loads that run for 3 hours or more are continuous loads and that breakers must be 125% of continuous loads. This is why the cable that comes with the car is only 12 Amps as 12 x 1.25 = 15 so you that's why the car should be plugged in to its own circuit. This is also why the level 2 EVSEs are 30 or 32 Amps but need to be wired on a 40 Amp circuit. So for a circuit you add up all the loads that run less than 3 hours and then add on (1.25 x 3 hour loads).

JejuSoul is in Korea, I don't know if they have the same definitions and restrictions on the continuous load as we do in North America.

 

[kiastormtrooper]

Thank you for the explanations. I don't understand why the car isn't able to adjust the charge rate to prevent tripping the circuit. At a quick-charger, I see the amount of charge goes down after 80% but the car continues to charge. What would be different if there was a change in power at a home evse? Shouldn't it detect a change and adjust its charging rate?

 

[notfred]

You can only detect Volts not how many Amps the circuit can supply.

A common way to think about electricity is to use a comparison with water, Volts is like water pressure so can be easily measured, but Amps is like how much water is flowing and until you get to the point where you can't draw any more water through the pipes you don't know if you have thin or fat pipes supplying you.

For car charging the EVSE tells the car how much current the car can draw, but that is just based on what type of EVSE it is. Some of the Level 2 EVSEs even have switches to set what the car should draw based on the circuit it is wired in to. For the Level 1 cable it is set to 12 Amps as I explained earlier and with instructions to have the EVSE as the only thing plugged in to the circuit.

The Level 3 chargers reduction in current at 80% is because that's what the battery can take so it slows down at that point, nothing to do with the Level 3 charger detecting how much current is available upstream from it.

Theoretically you and the Leaf owner could open up your L1 cables and reprogram the little computer in there to tell the car to only draw 6 Amps all the time, but that would suck any time you aren't both plugged in at the same time. The only practical thing is to get the two EVSEs plugged in to two different circuits, best of all would be to put 2 L2 EVSEs in the condo.

 

[wrickcook]

notfred is spot on.
Use different circuits, or do it right and install a L2.

I know I plan on eventually having two EVs, so I just had two NEMA 15-40 outlets installed at the same time (even tho I only need one right now).

 

[ralyon]

A circuit beakers purpose to to shut off power before damage occurs. First, some power is lost in transmission so when you are pulling 12A at the outlet, the power coming across the breaker is actually slightly higher than that. So if you were to try and pull 15A, you would trip the breaker since you would be over the rated amps at the breaker itself. This is because the wiring and outlets installed for that circuit are only designed to safely handle at least 15A and if you were to pull more than that it could over heat and start a fire inside the walls.

Each car should have a circuit dedicated for it to charge on so if you wanted to charge both at the same, they should each have their own circuit or a circuit rated at 2.5 times the charger (25% higher than charger 1 and charger 2 together). So on a level 1 the charger is rated at 12A and the standard house outlet (NEMA 5-15) is rated at 15A so you have to have separate circuits. I have seen both 16A and 30A level 2 chargers so technically you could run two 16A chargers on 1 circuit for a NEMA 14-50 (50A), however an electrician would have a separate circuit for each NEMA 14-50 outlet anyway.

 

[notfred]

ralyon - not quite, power loss in transmission is voltage drop not current, but your conclusions are correct.

 

[kiastormtrooper]

Thanks again, for the explanations, folks. I've read that multi-family dwellings had issues with installing EVSEs, but I had no idea that each EV owner would need to have their own dedicated outlet to charge their car; it's impractical in this situation. It's ironic that the environment that is ideal for EVs -- multi-unit dwelling, in a high-density city -- is the worst environment for an EV owner.