Seriously, I am still unsure what the actual question is...

 

That's a good question but the answer is a bit tricky. The battery capacity depending on model year is somewhere between 16-18 kWh, but you lose some energy to resistance and heat and such, so you can probably tack on another 1-2kWh to the actual capacity of the battery. But what she wants to know is how much power does the car pull from the grid while charging.

Maybe she can glean what she needs from this:
1120V charge
120*8= .960KW, .96 * 8 = 7.68 KW-Hr 8 Hours at 8 amps
120×12=1.44KW, 1.44 x 6 = 8.6KW-hr 6 hours at 12 amps

240v charge
240*16=3.84KW, 3.84 x 3 = 11.52 KW-Hr 3 hours at 240.

 

For a gen 1, it's somewhere around 12kw to fully charge. As far as charge rate, you have options based on the chargers. For the 120V charger, you can draw 8 amps (960 watts per hour) or 12 amps (1440 watts per hour). With a 240V, you'll be limited to the options of the charger to limit the current. My 240V charger has a number of settings internal of the unit that will let you set a maximum charge rate, which is limited on the high side by the 3.6kw per hour rate of the internal charger of the Volt.

 

Just FYI, "watts per hour" is incorrect... it's the equivalent to saying "horsepower per hour". Power (watts) is instantaneous. Amount of charge is in kWh (energy).

 

it takes roughly 11.9 KwH to Fully charge my Volt’s(Gen1) depleted battery.
http://www.mychevroletvolt.com/chevy-volt-energy-usage-charging-on-240v-vs-110v

 

A very rudimentary rule of thumb is to simply use the capacity of the battery. This will be an overestimation but does included the inefficiencies of the charger, wiring, etc. So if the Volt has a 16 kWhr battery, then figure 16 kW's of electricity to fill it from empty. Basically, this would give them a worst case scenario with a built in buffer.

A pass-thru meter such as a kill-a-watt device will give you a much more accurate number. There are some folks here who've done that and will be along to post their figures. Some EVSE units also report usage numbers (draw) via wifi.

 

Power is kW. Energy is kWh. The power draw is 3.3 kW. I suspect this is what they're interested in. The energy draw depends on how many miles you drive at roughly 3 miles per kWh.

 

There is a missing part to your sisters question. How much do they normally drive each day. I own a Bolt EV and my grid connected house is not setup to replace the full 238 miles range each night. But I can replace easily the 50 miles I drive each day to work. So the solar system would need to be sized big enough to replace the battery charge they normally use each day. The Volt may the perfect choice because you can always fall back on the ICE to power the car if needed.

 

To really understand what's needed, you have to crank in the normal use case - how many miles do they expect to drive on a typical day? Are their habits consistent, or do they very a lot?

Any modern EV runs between 32 and 38 kWh per 100 miles from the wall - including the Volt (some PHEVs run higher, but they are unusual cases.) Using the higher end and the traditional "12k miles per year," you get about 4500 kWh per year - just over 12 kWh per day on average. If they live somewhere near you in NC, it looks like they should have around 5 hours of equivalent insolation for an annual average - which would mean 2.4 kW of solar panels would just about cover the "average" user in any modern EV. This is all averages, though - without the grid backing them this assumption set might cause problems in the dead of winter. (A Volt could just run on gas at that point, of course.)

The power draw itself isn't really important - the cars can all be told to respect a limit you put in place by settings on the EVSE, all the way down to about 600W on 120V if necessary - and all the cars can take at least 3.3 kW from a 240V, many of them can take 6.6kW and some can take 10 kW or more if you have it handy.

Of course, you need to give the car enough power to recharge the miles you drive daily in the time you have - which is why it all comes back to the driving habits and expectations, for a Volt or any EV.

Depending on where they live, if you do have an unexpected trip somewhere distant, there may be DCFC options for the EV away from home to make up the difference (but I wouldn't want to count on them for a daily charge.) Tesla has a much more extensive network than the others at the moment, but other options are getting better as well.

 

also ,
Most off grid people would have no problem with DIY car charger cables and with the correct pilot wire signal
the volt can use 120 volts AC at 6 amps.

 

The car never charges to 16-18 KWh. It's more like 10-11 useable KWh and add a kw or 2 for efficiency/cooling,
etc. That's for a full charge from "zero"

Minimum draw for OEM EVSE is 8 amps. At 120vac that's 960 watts.

 

I tell people that it's like running a hair dryer for 13 hours to go from empty to full on my Gen 2.

 

I like your analogy. Probably something helpful that the off-grid people can relate to. An electric space heater would be another good one. The other issue is when the car gets used and when it gets charged. Implies battery storage could be key factor, maybe even more important than how many kilowatts worth of panel they have.

 

If they are concerned about the "power draw", the answer is 8 amps (maybe 6?) at 120V, on up to 16 amps at 240V.

Each 120V amp will replace about 0.4 miles of EV driving per hour connected (120V x 1a / 1000 x .85 x 4). The other assumptions are that charging efficiency is 85% (90% for 240V) and that the Volt can go 4 miles on each kWh.

Using this formula:

an 8 amp, 120 V connection will replace 3.2 miles per hour,
12 amps @ 120 V will replace 4.8 miles per hour,
12 amps @ 240 V will replace 10.4 miles per hour,
16 amps @ 240V will replace 13.8 miles per hour
​

As others have said, your sister needs to know how many miles of EV driving they want each day, and then determine if they have sufficient daylight and surplus kWh during the times the car is at home to generate that much juice. Of course, the Volt runs on gasoline, too, so if the days are cloudy they can still drive the car, and it's pretty efficient there, too.

 

Plus they can charge away from home, if they happen to have a charger at work or where they shop, etc. In a best-case scenario, that could make the car practical with zero demand on their home system.

Another consideration is that since the car can either store or generate a lot of power, it could potentially power their home, if needed, and thus increase the dependability of their home system. However, if they already have a reliable backup generator, this is not much of an additional benefit.

 

Many good answers already, so I won't echo them. But one additional thing: some/most EV manuals state the car must be charged from normal grid power. It will probably work with a decent quality off-grid inverter setup, but if it doesn't, that's on you... you won't get any support from the manufacturer. I'd want to test it first, or find someone else who has tested your exact setup, to be sure it all works.

 

1-3.3kW (3.6kW) for 4-12h depending on model year and charge required.

Minimum sustained power required is 1kW (8A @120V).

For winter standby heating, it will pulse off an on as required, up to 1800W. (if on L1 it should max out at what the L1 setting is, e.g. 8A@120V)
Summer cooling similar story, but AC can use more power and will dip into HV capacity where available if temp is critical.

 

I haven't tried it, but I'm pretty sure the car will respect the 6 amp limit that's the lowest J1772 Pilot signal, so if draw was really critical you should be able to get it down to ~720W or so on 120V.

Of course, then it takes a small forever to charge, and that's when it's not freezing out. You need more power overall that way, too, because the overhead involved in keeping the computers awake and the TMS cooling/heating the battery pack becomes a big chunk of the power draw.

 

I have a 2017 and a solar system but not off grid. I have attempted to gage the impact of charging on the system and do not believe peak draw ever exceeded 4KW. It's fairly obvious that the amount of power used going to be slightly higher than the battery capacity you are filling (18.1KWh from zero to full plus a small factor for inefficiency). However, I am guessing your sister and BIL want to know what the momentary electric draw will be. 4KW should cover it. Draw goes down as the battery starts to get full. Charging begins hard and slows down as it progresses.
I can attest that charging an electric car, even a Volt, is a major hit on your solar electric generation. My system is 8.8KW in Pennsylvania and some days the car takes half (sometimes all) the electric generation. Depends on the weather, season, efficiencies and how much you drive the car every day.

 

If limited to 120vac, the maximum draw is only about 1.5 Kw. The battery is NEVER filled to the full 18 KW-Hr. capacity. It's more like 14 KWhr useable capacity. People seem to keep forgetting that the Volt doesn't charge to battery to 100% nor discharge to 0%. I have a 10 KW system grid-tied. I get anything from 0 to 50+ KW-hrs per day and the car doesn't charge up from empty every day. That means much of the time the panel production exceed the Volt's consumption.

 

I can confirm at least a 2014 Volt will go down to 6A/720W, my measurement showed about 760W actual. J1772 protocol requires that the car respond dynamically to changes in the Pilot signal even after charging starts.

 

That second tidbit is probably most interesting to an off-grid person who has the knowledge/desire to make a custom EVSE that goes as low as 6A:
Create a brain that can check the input power in real-time and dial up or down the pilot signal to optimize energy use vs waste, dial it down when there are other electricity draws in the house, etc.

 

smarti.....thanks. I saw the 18.1KWH battery and wasn't really sure if that was the total battery size or the usable size. I assumed it was the usable size. I never considered off-grid as my house can't support enough solar generation to sustain itself even without charging a car. I'm total electric here and in a suburban setting with limited roof and basically zero ground-mount options. I still look at grid-tied solar as a great deal, but I can't look it as power utility replacement....just supplement to reduce my use from outside sources. The off-gridders have a lot more to consider with storage, generation and available current over a 24 hour period. Grid-tied with net metering it does not matter, as you know.

 

I know a couple of off-gridders and their systems. These are small remote homes powered mostly by solar panels, large battery banks and efficient inverters.

These systems are really not designed to charge electric vehicles. The amperage draw is too great. Most off-gridders avoid having large amp drawing appliances such as anything with a large electric heating coil (electric dryers, toasters, kettles and even microwave ovens). They tend to use propane or wood or gas for heating.

Any electric vehicle would really draw too many amps for too long in such systems and would not be feasible for most off-grid small home situations, IMHO.

 

Lots of good info here so far! Here are some screen shots of my Outback Radian Inverter while charging my Volt with an L2 Charger at 16 Amps. "Power Draw" from the 48V Battery Bank is about 90 Amps. If you don't have a good sized Re system, Solar, Wind or Hydro, then max charging the Volt will be difficult or impossible. But not everyone needs or wants to charge at max. I put about 15 miles a day on my Volt so a little here, a little there is all that's required.

 

Hi,

I've been using a stand alone solar power system at my house in Australia for the last 15 years (i.e. no mains power at all). I originally had a 48v 1500A/H battery bank, and a 2.5kw solar array, but about 3 years ago we upgraded the system when we bought the Volt to 10kw of panels. Around the same time the original battery bank started to fail (about 3 of the 24, the rest were okay), so I swapped out for 940A/H of gel batteries.

I charge the car very comfortably at the 10A rate on our 240V system, and it's finished after about 6 hours. Overnight I let the car charge at the slower 6A rate off the bank, and usually find we're down about 300-350A/H in the morning (depending on the time of year I can usually squeeze an hour or two of usable recharging in at the end of the day). With 10KW of panels I recoup that in a couple of hours and we're always in float at the end of the day.

Our inverter is the original one which is 5KW continuous, so the 2.5KW draw of the car at 10A is no problems at all. I've spoken to a few other people who charge their Imiev off their system much the same way.

I'm assuming this is what the original question was asking. Looking at my inverter the car generally seems to draw about 40A/H on the DC side at 6A 240V or around 60A/H on the DC side at the 10A setting. If their PV is capable of meeting that load then there's really no problem. It would just depend upon whether or not they have enough battery capacity to consider charging it at night. Since we have the benefit of the engine as well, sometimes if it's particularly rainy we don't bother since I'd rather have the house in float each day than run it right down and then have to use the generator. That said, with 10KW of PV I can still charge at the 6A rate and get enough power to meet that on an overcast or lightly raining day.

We've been thinking of getting a Tesla model 3 or the new Leaf, so getting an L2 charger for the Volt would be good so we could get it charged and out of the way and then spend the rest of the day on the other car.

Anyway, the bottom line is it's quite doable if the system is sized correctly. We run an air conditioner, welder, clothes dryer etc off our system without any problems at all. Some off-grid systems might be much smaller for cabins etc, and that might present a problem, but for a residential style setup that is setup to run normal household appliances, it shouldn't be an issue.

regards,

craby

 

craby: very interesting to read your off-grid setup. I would say your system is, in my experience anyway, a lot larger and more capable than any of the ones I have seen, which was the reason for my post above. You also are fortunate to live in Australia with considerably more available sunlight than where I am from (Vancouver Island). Our winters here, no matter what size of solar array, would never be able to charge up a Volt on a consistent basis. It might be possible with a large wind generator addition, but again, only if one were fortunate to live in a position to capture that wind.