EV Chargers: How to Choose the Right One for Your Home

Discussion in 'Tech: Batteries, Charging, Alternative Energy' started by EyeOnRivian, Aug 20, 2019.

  1. EyeOnRivian

    EyeOnRivian Well-Known Member

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    Just watched the latest E for Electric YT video where the host (Alex) had EV industry expert Tom Moloughney go over some of the key factors to consider when selecting a L2 EVSE for your home/garage. I'm sure there are people on this forum that don't have an EV yet or may be upgrading their current EVSE (aka home charger) that just might find this video helpful. Tom provides some good info / tips that I thought was worth passing along here. (Note: video is slightly on the long side at about 40 or so minutes. To save some time I played it back at 1.25 speed and had no problem following along.)



    What do you think about Tom's key factors to help determine the proper EVSE for your scenario?

    Maybe share some noteworthy info on your EVSE (e.g. charger brand, model details, kW, amps, NEMA rating, amps, UL certified or not, installed in or outside, any charging cable length issues, portable or hardwired, etc.), along with what your primary factors that led you to purchasing/using it (e.g. EV charger kw, battery pack size, smart-charger, price, etc.) and is it meeting your expectations/requirements (e.g. pros, cons, recommend / not recommend, etc.).
     
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  2. ajdelange

    ajdelange Well-Known Member

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    #2 ajdelange, Aug 22, 2019
    Last edited: Aug 28, 2019
    I think the most relevant thing here to potential Rivian owners here is that the Rivians are bigger vehicles than even the biggest Tesla (the X), thus use more power and will, thus, take more time to charge with the usual sorts of chargers that the video talks about. We can only do some rough numbers from what we know at this point but the Rivians will have about 400 miles of range from a 180 kW battery. Dividing the watts by the miles we easily see that the Rivians power consumption will be in the neighborhood of 450 Wh/mi under nominal conditions. Throw in winter cold or desert heat and that is going to go up as it will when off road, when driving in rain or snow and in unusually hilly terrain but lets stick with 450 as a sort of nominal everyday use number. The rules for EVSE change if the circuit current is over 60 amps. So lets assume that we install a 60 amp circuit. We must derate that to 48 A (as this is EVSE we're powering). At 240 V 48 A gives us 11.52 kW. That's the advertised size of the Rivian charger. Coincidence? Chargers are not 100% efficient so of the 11.52 kW we get from the EVSE perhaps 10.4 kW are delivered to the battery. In an hour it picks up 10400 Wh which, at 450 Wh/mi means 23.11 mi range added per hour of charging. To add 400 miles would take 400/23.11 = seventeen point three hours (note that I had to spell out the hours as if I put numerals the server hangs). This is, of course, completely tolerable if you drive, say, 200 mi/day. But keep in mind that any charger wired into a 50 A circuit or plugged into a 50 A receptacle (14-50R) can only deliver 40 A legally and will only deliver 5/6 of these numbers meaning 5*23.11/6 = 19.3 mi per hour or 20.8 hours for a full charge. Again acceptable for many applications. Further note that a 14-50R receptacle can be legally installed on a 40 A circuit. In an abundance of caution Tesla has modified its 14-50P adapter to only deliver 32 A should this be the case. 32*240/450 = 17.1 Wh/mi (23.4 hr for a full charge). I think the message her is to select a charger that delivers as much current as possible. This isn't a Leaf you are charging.

    Another thing to think about is the future. Will this RIT be the only BEV you will ever charge or will there be an R1S arriving about a year later? How will you charge 2 BEVs? This is something to think about now as clearly you will want a circuit of more than 60A and the rules get a little trickier over 60A. Unless of course, you want to install an entirely separate 60 A circuit. If you live in a house with 200A service this is going to be a challenge which will probably involve a larger service (bigger panel, bigger transformer on the pole...).

    One comment on the video: he says a couple of times that your car will be the biggest electric load in your house, That depends, of course, on how much you drive. If you do the average 13,000 miles per year that will be, at 450 W/mi, 6 MWh/yr. I use about 20 MWh/y overall. YMMV and you can look at old electric bills to see what part of your annual use the BEV will take.
     
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  3. ajdelange

    ajdelange Well-Known Member

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    #3 ajdelange, Aug 22, 2019
    Last edited: Aug 28, 2019
    Forgot that info on subscribers current installations was requested.

    In Virginia I have a Tesla HPWC on a 100 Amp circuit. As the circuit is above 60 A there is a lockable disconnect installed. It is capable of charging my Model X at 72 A (17 kW). It can be set to charge at a lower rate if desired. It can be set up as a master among other HPWCs on the same circuit and will share power between itself and the slaves. It is NEMA 3R ("Protection against incidental contact with enclosed equipment. Protection from falling dirt, rain, sleet and/or snow. Drainage provision. Protection against rain at a level higher than the lowest live part.") rated, is installed indoors, has a 24' cable. "Smart" and internet charging features are handled by the car. Current consumption is measured by external equipment (eGauge which monitors many loads in the house and the solar panels) as well as being recorded by third party apps which communicate with the car. Car has a 100 kWh battery. Unit costs $450. It does everything it is supposed to do and is fairly attractive.

    In the country I have a corded HPWC plugged into a NEMA 14-50R on a 50 A circuit. It charges my X at a maximum rate of 9.6 kW (40A).

    None of this will be of any relevance to Rivian owners unless, as many of us daily pray, a SC network deal is struck between Tesla and Rivian, and thus a Tesla to Rivian adapter of some sort becomes available.
     
  4. ajdelange

    ajdelange Well-Known Member

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    I have to take back the comment about no relevance to Rivian owners as I have just learned of the TeslaTap which would allow a Rivian owner to charge from a Tesla HPWC (but not from a Tesla SC).
     
  5. Lmirafuente

    Lmirafuente Well-Known Member

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    Thanks for sharing...this was very helpful!

    I am in the process of building a new house with solar. Does anybody in this forum have information on how much a EV (Rivian) will add to the consumption of electricity? I guess is we will be around 400kw hours per month without the Rivian....how much will the Rivian add to the consumption of energy?

    I do not have an EV to draw first hand experience. Thanks for the help in advance!
     
  6. ajdelange

    ajdelange Well-Known Member

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    #6 ajdelange, Aug 28, 2019
    Last edited: Aug 30, 2019
    That depends on how much you drive it just as the amount you spend on gasoline depends on how much you drive your ICE cars. You start calculations by looking at Rivians statements that the long range version will have range of 400 miles and carry a 180 kWh battery. Simple arithmetic say then that the power consumption will be 180/400 = .450 kWh/mi (450 wH/mi). Each 1000 miles driven then requires 0.450*1000 = 450 kWh. If you drive 1000 mi per month (note that the average American drives about 13,000 miles each year) you will be putting about 450 kWh into the battery meaning that you will be taking something over 500 kWh from the grid/solar as the charger is not 100 % efficient. That's more that your estimated load of 400 kWh/mo which seems awfully low as 400 (kwH/mo) / 31 (da/mo) /24 (hr/da) = 0.538 kW/hr/hr = 0.538 kw average demand. A modest sized home will have an average demand of at least a kW. I have a moderate sized home heated by heatpumps (i.e. electricity) with electric backup heat and averaged 6 kW during the cold months.

    To compare to the Solar system get the NREL (National Renewable Engergy Lab) numbers for where you live. Typically April - Jul on the east coast gives us the equivalent of about 5 hours per day of sunlight at the level at which the panels are rated. Thus a solar system rated for 10 kW at peak sun will give about 10*5 = 50 kWh per day. If you are an average user of your vehicle you will be driving 13000/365 = 35.6 miles each day. At 0.450 kWh/mi that will required loading the battery with 0.450*35.6 = 0.94 kWh each day. Thats only about 10% of a 10 kW system's capacity.

    California has, I believe, some strange regulations concerning the size of residential solar systems that can be grid tied. For this reason and because your driving habits and home power utilization are likely quite different from the examples given above you really need to consult a professional. It can get complicated fast.
     
  7. Lmirafuente

    Lmirafuente Well-Known Member

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    Thank you!
     

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