Charging on a 50 amp service?

The charger in the car and the charging station negotiate how much current to provide. The maximum the Prime charger will accept is 16A. Having more available from the charging station is not relevant. My home charging station will provide up to 32A, and is plugged into a socket rated at 50A. This is just future-proofing on my part.

 

Normally, every thing is fine, as CharlesH said. In his configuration if something goes wrong in his EVSE and it starts drawing 45 Amps, no breaker will trip. That is a lot of extra heat in his home that may start a fire. Having a correctly sized breaker for the load you expect is a good safety precaution. However, it will work.

It is perfectly safe to have wire rated for 50 amps protected by a 20 amp breaker, so you or an electrican could just swap a 20 amp breaker for the 50 amp breaker. (then you could use a 20 amp receptacle)

 

I wouldn’t do it, especially in a workplace setting where an inspector might decide it violates California Electrical Code sections 110.3(B) or 240.5(B)(1). I don’t think I could claim that a charger cable with flexible cord and other parts designed for 16 or 20 amperes would be adequately protected by the car itself, which may have some internal protection but is not a listed overcurrent protective device.

From Toyota’s New Car Features book, available by subscription to techinfo.toyota.com:

FAIL-SAFE

(a) The electric vehicle charger assembly has a self-protection function and automatically limits or stops power output in the event of overvoltage, overcurrent or excessive-temperature.

(1) If overvoltage or overcurrent is detected, charging is suspended.
(2) If an abnormal temperature is detected, the charging power is reduced.​

They don’t mention a conventional fuse or thermal-magnetic circuit breaker, though, which also wouldn’t be consistent with charging being only “suspended,” nor do they define “overcurrent,” much less give a rating or characteristic curve. The “electric vehicle charger assembly,” by the way, is inside the car; in Toyota’s terms, the charger cable is the “electric vehicle charger cable assembly.”

 

It can matter a LOT.

What are you going to "adapt" it TO ??
To your 115 V charging cable ??
If so......very bad idea.

 

A 50 Amp circuit will have a breaker that will protect the wiring up to 50 Amps. Notice I said wiring. A circuit breaker is designed to protect the wiring only. In your house you have a bunch of 15 Amp and 20 Amp circuits but most of the time you are only drawing a few amps from that circuit.

You are OK as long as the extension chord you use is rated for for the current draw your Prius calls for. Somewhere here I read 16 Amps.

 

The EVSE has its own breaker and gfi there is no more fire hazard doing this than plugging an oversized EVSE into a car that can’t use the extra capacity,

If it’s against the law the law needs to change.

 

In my case, I have a 32A Chargepoint Home charging station which comes with a NEMA 6-50 plug. The charging station is designed to supply up to 32A, and to be plugged into to a 50A outlet, so I don't see why this is a safety concern. My breaker box is literally on the other side of a garage wall from where the outlet is, so the entire run is about 4 feet. I trust the electrician to have installed the outlet up to code.

 

it would be an interesting failure modality to have the evse draw over it's maximum, but just under the threshold of a larger external breaker. I would highly doubt anything in the charging circuit could do that. They're very complex devices that can function as either a constant current or constant voltage source and have very complex feedback mechanisms to do so. they also employ lots of safety mechanisms to keep charge from being present when the car doesn't want it (e.g. the charger has to be signaled to turn on, the car has to enable itself to receive it, etc.), and they're all designed to not kill someone fiddling with the plug in pouring rain or snow.

what worries me more is that someone who felt the need to ask is willing to wire up an adapter for things that are operating with lethal voltage/currents with inadequate knowledge.

does anyone know if the plug is solenoid protected? I would expect it to be so, but don't have access to the wiring diagram.

 

From a fire hazard, electrical code conformance, etc. perspective, this seems fine.
My only concern would be that under no circumstances should there ever be more than 16A flowing through that circuit to my prime.
Yes, the wiring between the breaker and charging station can support more...But it should never happen
Yes, the chargepoint can supply more but as long as a prime is plugged into the other end, it should never happen.
If it were my house, assuming I didn't also use the outlet for welding or such, I would likely swap the 50A breaker with a 20A one for an added level of protection. I'm comfortable doing that as I've spent many hours installing/replacing circuits in my home. I probably wouldn't go as far as to call an electrician to do that.

 

I know my GE durastation has built in fuses. I thought all EVSEs had built in protection, maybe not?

 

Certifications, like UL LIST, require it.

Some charges, such as my JuiceBox, allow you to specify maximum draw via their app. So, you can have it on a lower rated line.

Prime is smart enough not to request too high of a draw anyway. That's why the standard SAE J1772 at most public chargers works fine. No big deal.

 

No smarts needed -- the Prime is limited to 3.3 kW

 

People with RVs typically carry several adapters so they can plug their vehicle into whatever outlet is available. So long as the voltage is correct (don't try plugging a 120 V device into a 240 V outlet...), it should be ok. Normally any device you plug in uses lower current than the outlet is rated for. Think a 100 watt light bulb (less than 1 amp) plugged into a 15 or 20 amp household circuit. The problem occurs when you try to use a larger load than a circuit is capable of. In which case the circuit breaker or fuse blows. If the plug doesn't match the outlet, see if you can buy an adapter at an RV store (or even the RV section at Walmart). Plugging a 120 V device into a 240 V outlet is more complicated, but there are transformers available available that will handle that situation as well.

 

It’s fine to connect EVSE to a 50 A circuit, as @CharlesH does, if the EVSE is designed to be used on such a circuit.

@bobjames868 asked about something else, though: using EVSE with a 20 A plug on a circuit with a 50 A receptacle outlet and circuit breaker. I still think that’s not a good idea.

A circuit breaker or fuse for a branch circuit also provides primary overcurrent protection for the receptacle outlet or fixture wire (if any) and for the utilization equipment connected to the circuit.

In general, equipment is designed to be connected to a branch circuit of a particular rating. If the equipment can’t handle the maximum current a branch circuit of that rating can provide, then it has to include supplementary overcurrent protection at an appropriate, lower rating.

If the equipment can handle the full rated current of the branch circuit, however—as might well be the case for an EVSE designed to supply 16 A from a 20 A branch circuit—then it may not have to include any supplementary protection. The manufacturer can just tell you the required branch circuit rating or type of outlet in the instructions. The code sections I mentioned before require such instructions to be followed.

GFCI (CCID), yes; circuit breaker or fuse, perhaps not.

Are you sure about this? I haven’t paid $505 for the latest edition of UL 2594, Standard for Electric Vehicle Supply Equipment, and I’ll take your word for it if you have, but I have some contrary evidence:

• Leviton wrote, in U.S. patent 8,633,678 for an overcurrent protection circuit, “The UL standards...only require interrupting power in response to a differential current.”

• SAE J1772-FEB2016, Surface Vehicle Standard: SAE Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Coupler, gives a choice like I mentioned above:

5.5.1 EV/PHEV Cable Ampacity Coordination

Vehicle cabling used for the AC Mains and Equipment Ground should be coordinated with the supply input from the EVSE (known from the Control Pilot duty cycle). The following are examples of possible methods coordination may be achieved:

1. Sizing the cables for maximum EVSE supply input.

2. Provide circuit protection, such as fuses, for the cables.​

• In the Owner’s Manual (page 108) and New Car Features, Toyota says their charger cable is protected against electrical leakage, plug overtemperature, and transients, but they don’t mention overcurrent protection as such. Has anyone done a teardown on a Toyota charger to see if it has a fuse, circuit breaker, or Leviton’s patented circuit inside?

To be clear, I know some EVSE does have supplementary overcurrent protection, but it may not be something you can count on, especially with a 20 A, cord-and-plug connected type.

 

Aw come on. The only electrical device in my house that comes close to equaling the outlet capacity is the toaster in my kitchen. Most devices draw much less than the 20 amp outlets can handle. Like the wall wart that charges one of my electronics devices that takes 0.2 amps. It doesn't even have a 3 prong plug. Scary. And the 7.5 amp toaster with a metal case, 2 prong plug, and no fuse or ground fault circuitry. Really scary. How have we ever survived all this time with such dangerous electrical devices as toasters, microwave ovens, plug in air conditioners, etc.

EV charging may be new, but we've been living with similar capacity electric devices for a long time.

 

yuppers, you're answer is spot on. do people really think that their usb charger is capable of handling 15A at 120V? if you pushed that much current at that voltage into one of them using a constant current source it would just explode all over your kitchen counter (you'd see a nice example of that SED (smoke emitting diode) at work).

The thing to consider is where the failure would occur. The only place such a failure could occur and not be protected would be from the wall to the charger. Everything after that is protected by the charger and the evse itself. The only potential modality would have to be a short on the supply line to the charger and the wall. Possible... maybe, but you'd have to get JUST the perfect short. (even a 15A wire can handle 50A for a short period, albeit it will get hot, but it would still allow the breaker to blow).

 

No, which is why chargers for electronic gadgets have supplementary overcurrent protection, usually a non-replacable fuse or fusible resistor inside.

The toaster’s line cord and internal wiring are sized for the worst-case current draw of the heating elements; there is no mechanism for an overload. It’s protected against shorts by the branch circuit breaker, and against ground faults by the GFCI the code requires for kitchen receptacles.

Do you have evidence that an EVSE, of a plug-and-cord connected type intended for use on a 20 A or 15 A branch circuit, is required to provide any overcurrent (as opposed to ground fault) protection?

 

The 220 vac voltec charger has a well known issue with the in line fuses being blown or damaged (the 110vac Orange cord voltec has the same issue)

 

ok, so you ruled out one failure modality in your toaster... what happens if something or someone accidently shorts the hot to neutral. the gfci won't blow as you have an equal load, but I bet your cord will get plenty hot!

sure, the same thing can happen in your car, or in anything that's connected to an outlet.

the car charger is an active device. it will only draw as much as the biased power transistor arrays allow it to draw (being very simplistic here as lithium ion chargers employ both constant current and constant voltage chargers, and I haven't looked at the design).

i'd be very interested in seeing the schematic of any Li charger that could fail in such a manner.