I am new to this forum so I apologize in advance if this question has already been asked and answered. I am considering purchasing an EV as a station car. I have a normal household 15amp outlet in my garage, and was planning to use that as a charger in my home instead of installing a 50amp dedicated line. I can use chargers at station and really don't plan on putting that many miles on it everyday. So I figure, not necessary. I have a heater running in garage on same circuit. When that comes on, it will use some of the amps going into car. How does your EV know not to pull all the electricity on that circuit so you aren't constantly dealing with circuit breaking? Is it regulated by the EV or the line connected to the outlet? Is it model dependent? Hopefully someone here can explain the engineering of it, salesman I have encountered at dealerships haven't given me acceptable technical answers. Thanks in advance
I don't know about all EVs, but mine has different charging rates so I can set the vehicle to control the current draw. The other way to do it is with the EVSE (charger) you use. It's more common to have that control in a Level 2 EVSE (240 V), but the Level 1 cable that came with my car is limited to 10 A, so it won't draw more than that even if my car is set to a higher value.
It won't "use amps going into the car". If the amps drawn by your heater plus the amps drawn by the car plus whatever other amps you may not have considered that are on that circuit (shop lights? Cordless appliance batteries being charged? Outdoor flood lights? Garage door opener? Everything counts, even if you think it's negligible) is greater than 15, the breaker will trip. No car can know anything about other stuff you've got running on that circuit. Picture the scene in Apollo 13 where Gary Sinise is turning various switches on in order to keep the amperage below 20 amps. That's a big reason why people get dedicated circuits for their chargers, so that they know there's only one thing drawing electricity.
Some EVs allow you to control the current ( amps ) others do not. Which EVs are you considering? What is the wattage of the heater you are currently running? If it is using most of the current for the heater you may not be able to set the charger low enough with the car. In which case the heater needs to be off during charging. One option would to be put the heater and the charger on timers so that they don't run at the same time. Or simply turn off the heater while the car is charging.
Conventional circuit breakers are not designed to operate at full load for more than 1 hour in a 2 hour period, only at 80% of the rating. ie: 15 Amps *120 Volts = 1800 watts, but only at the circumstances detailed above. At 80% this will allow 1440 watts max (12 amps) - an electric car will draw current for longer than that 1 hour usually ~ 10 amps using the charger (electric vehicle supply equipment called EVSE) that is supplied with most EVs. This is not standard and must be checked when purchasing your EV. As described in above post, the charging current can be adjusted to a lower setting with some electric vehicles. Not sure what you mean by "purchasing an EV as a station car" but if spending the $ on an EV it would be well advised to install a dedicated 120 volt receptacle on either 15A or 20A rated circuit, class A ground fault would add extra protection, as most EVSE equipment is class B rated (20ma as opposed to 5ma trip rating) One thing that is standard, the car does not "know" how to limit the current...that is up to the owner/operator...the car will want as much juice as it's on board charger will allow depending on the settings set by the user. I would definitely not share an outlet (or circuit) with a heater and an EVSE. Hope this helps BTW... welcome to the forum
Thanks for the welcome and thanks for the posts. Pretty clear a dedicated line the way to go. Or at least make sure everything else is off.
I faced this problem when I got an EV, which I mostly charge at home from a wall socket. My garage is on the same circuit as my laundry room and part of the kitchen, and I already occasionally flip a breaker with too many appliances running at once, so I paid to have a dedicated 20 amp circuit installed to charge the car. It cost only about $150 and was more than worth it to know I can charge anytime, no matter what else is running.
Good discussion so far, but a few points need to be made clear about AC charging: The EVSE (the gizmo on the wall/electronics in the box inline with the cord) signals to the car a maximum current via the control pilot (CP). The maximum can be set as low as 6 amps, and can change over time during charging. Cheap chargers (like the ones that come with cars) will have a non-adjustable maximum limit (often 12 amps), but nicer chargers let the user adjust the limit. Really fancy chargers would be able to communicate with other devices in the and dynamically allocate the available current between loads. The dynamic allocation is most common in cases where multiple EVSE are connected to a single circuit (e.g., a 60 amp circuit feeding two 40 amp EVSE, in order to limit the total load to under 48 amps). The EVSE doesn't know the car battery's state of charge. All it does is signal the maximum charge current, and also connect and disconnect the AC mains from the charging cable (using a relay) based on detection of the cable being connected to the car that is ready to be charged. (Plus some other safety related things too, which I'm not mentioning) The "charger" is actually in the car, not the EVSE. The charger contains the smarts to decide how much current to draw from the mains. It dynamically limits the current based on the battery's state of charge, battery temperature and also the EVSE's CP signal (and other factors...). The only external input it gets is from the EVSE's CP, so if you need to share the supply with other equipment, you need to devise a way to adjust the CP's PWM duty cycle. So, yes, you can do what you want to do, but it'll take some engineering effort. You would need to design a control circuit to that reduces the EVSE's CP PWM duty cycle when your heater is turned on. An easier solution would be to set your EVSE's limit to around 6 A and also limit your heater's current to 6A, so the load is never too high when both are enabled. One project to look at is OpenEVSE. With its WiFi model, you should be able to control the charger's limit over the network. It's a bit pricy, but I'd use it if I were to complete this design.
You might consider laying your own, 240 VAC 50 A line compliant with the local code. Terminate in a NEMA 14/50, all weather housing. Then hire an electrician to inspect and install a 50 A circuit breaker. You'll then be set for L2 charging. Nexts look for a dual voltage, 120/240 VAC, portable EVSE with an amp setting option. With a NEMA 5-15 adapter, you'll be free to charge pretty much anywhere from motels to RV parks. GOOD LUCK! Bob Wilson
The above post was in response to Jupiter Mike's question. Must have screwed up the attempt to quote hi..
