EVSE 120 VAC Charging Efficiency

[MrDRMorgan]

One of my earlier questions regarded the charging efficiency of the EVSE 120 volt charger that came with the Spark EV. Now that I have the car and have had time to figure out how it works, I have my answer - at least for the default 8 amp charging rate. Here is what I did:
1. Charged car overnight to full charge and green dash light blinks. Reset trip meter in the car to zero.
2. Drove car for about 35 miles on freeway at 65 mph average and in town for 17 miles at 35-45 mph for a total of 52 miles. The trip meter showed I traveled 52 miles at 4.6 mi / kWh.
3. Reset power meter at wall outlet to zero and then reconnected the car to the charger and allowed it to fully recharge again.

This is what I found.

1. It took 16 hours to recharge the car.
2. The total recharge as measured by the power meter was 14.41 kWh which, for the 52 mile test, averaged out at 3.61 mi /kwh.
3. Assuming the car's trip meter is accurate, the charging efficiency is 3.61 / 4.6 for a charging efficiency of 78.5%.

The 3.61 mi / kWh is the number I needed to estimate how many more kWh would charging the car add to my monthly utility power consumption. I expect this number to increase to approximately 4.0 as I learn how to operate the car more efficiently.

19 June 2015: 738 miles on the car now. The car was driven 36 miles around town yesterday with A/C running most of the time. I recharged using L1 charger at 12-amp rate over night which consumed 9.79 kWh as measured by my power meter at the outlet. This calculates to 3.68 mi / kWh. Assuming 75% charging efficiency, I would expect the trip meter to show 4.9 mi / kWh and this is close to what the trip meter actually read.

 

[Nashco]

MrDRMorgan, sounds like you've got some pretty sound logic there. As already noted in this thread, the lower the charge power is, the less efficient it is (due to parasitic losses in computers, pumps, etc.). I'll be interested to see the efficiency numbers you measure at L1-12A (maximum power with the provided L1 EVSE) and with L2 at 3.3 kW (max power of the onboard charger). Let us know if you do more testing at higher charging power.

Thanks,

Bryce

 

[MrDRMorgan]

Bryce,

I plan to test the 12-amp option in a few days. Unfortunately, I do not have access to an L2 charger. I will also be looking at what I get from an NRG eVgo fast charger. Hopefully, this will help others to make educated estimates for their own vehicles.

 

[Nashco]

You get a free (or nearly free after $500 discount) Bosch L2 EVSE with your Spark, I strongly recommend you get it even if you're not sure you'll install it immediately. It's a fantastic deal with no strings attached!

Bryce

 

[MrDRMorgan]

I will be sure to take advantage of that offer. We use a gas dryer at home but the laundry room is also wired for 240 VAC single phase. My plan would be to have the dryer wiring disconnected at the 30-amp power panel breaker and then use that breaker to wire up the L2. Hopefully, 30 amps is sufficient for the L2 charger.

Dennis

 

[ExtensionCord]

I will be sure to take advantage of that offer. We use a gas dryer at home but the laundry room is also wired for 240 VAC single phase. My plan would be to have the dryer wiring disconnected at the 30-amp power panel breaker and then use that breaker to wire up the L2. Hopefully, 30 amps is sufficient for the L2 charger.

Dennis

The good (and bad!) news with the Spark is it only charges at 3.3kW which is ~14a at 240v. You can get full charging with the Bosch 16a unit, no issues on a 30a line.

 

[MrDRMorgan]

Do you know which model of Bosch L2 charger is used for the special offer? I would like to download the installation manual and start figuring out where I will put it in my garage.

 

[ImTedBell]

Dr Morgan

This is the list of equipment you can get with the $500 discount. www.pluginnow.com/charging_stations

You will to pay shipping+taxes, plus any amount over 500. I got the 30a/18ft model for about 170 shipped.

I wasn't able to find a manual online, but what do you need from the manual?

Lastly, the amperage isn't adjustable. So don't buy a 30 amp model thinking you can turn it down.

 

[MrDRMorgan]

ImTedBell-

Thanks for the I info.

Please correct me if I am wrong but doesn't the Spark EV have a 3.3 kWh on-board charger and therefore cannot charge at a rate faster than 16 amps? Since I only have a 30 amp circuit available, it will not work if I have an L2 charger pushing out 30 amp current at the rated trip point of the circuit breaker. This is no problem if the vehicle's on-board charger limits the current to 16 amps even though the L2 charger is rated to provide 30 amps.

 

[emv]

A 30 amp circuit is sufficient for the 16 amp Bosch unit. 40 amps is required for the larger 30 amp unit. As long as you're having to have wiring restrung from the panel to the garage you could have a 40 amp breaker and wiring of the appropriate gauge installed. The only problems I could forsee would be if your house is old and has something like a dangerous Zinsco panel.

The car's internal charger controls the rate of charge, not the EVSE. Either the 16 or 30 amp units will work well with the Spark, with no difference in charging time. For a few dollars more I went with the 30 for future proofing and for the convenience of its longer cord.

 

[MrDRMorgan]

Thanks emv-

There is no problem with the breaker panel. When we built the home we included provisions for a 50 amp 240 VAC hot tub circuit. We never installed the hot tub but the panel has the necessary current carrying capacity for the L2 30-amp charger should I decide to install it. The 30-amp dryer breaker is the same size as the 50 amp breaker so the 30-amp breaker could be changed without a problem.

 

[Nashco]

While the Spark EV only has a 3.3 kW onboard charger, this is definitely behind the times (smart ED is the only other EV with a 3.3 kW charger!). If your panel has the capacity for a 40A (or greater) circuit, you'd be wise to get the 30A Bosch charger rather than the 15A unit. This will future-proof your installation, as the Spark EV is certain not to be your last EV ever and any other EV you get in the future will have at least a 6 kW onboard charger. It's a negligible cost increase if you plan on the 30A EVSE now, you'll thank yourself in the future for spending the extra few bucks now.

Bryce

 

[MrDRMorgan]

Bryce,

Good suggestion. It probably does make sense to install the larger capacity charger even though I may never use its full capacity and assuming the installation cost would be about the same for either charger.

 

[ImTedBell]

The 30A model is a 18 ft cord, vs 12ft for the 15 amp model.

 

[MrDRMorgan]

12 ft cord would probably work but a 20 ft cord would be better for me.

Did my first DCFC charge today at an NRG eVgo station in Tracy, CA. and it worked perfectly without a single problem. I started at 27% charge level and ended up at 99%+ after 25 minutes. The other two locations I need to test are at (1) the Livermore Premium Outlets in Livermore, CA and (2) the SMUD HQ in Sacramento, CA. Plugshare shows the Livermore location may have problems but the SMUD HQ seems to be working fine.

 

[SparkevBlogspot]

I started at 27% charge level and ended up at 99%+ after 25 minutes.

You may not want to go beyond about 80%. After that, charging slows down while you get billed by minute. DCFC at 99% is only 9kW (or less!) while billed at $6/hr ($0.67/kWh). This is like getting 21 MPGe when gas is $3.50/gal.

http://sparkev.blogspot.com/2015/05/public-chargers-in-socal.html

I think DCFC is too fast. I have to eat really fast to make it back to the car before it's beyond 100%. All the time beyond 100% is 0 MPGe. I set my phone alarm, but sometimes it goes off even before food arrives. I hope they fix the problem, either some automated way to disconnect DCFC for another to use or restaurants have faster service.

 

[MrDRMorgan]

Thanks for the heads up.
I did notice the slow down at the end of the DCFC cycle. The NRG eVgo stations I visited both charge by the minute so what you pointed out is quite true. From this point I will disconnect at 80-85% charge and save some money too.

At the Greenlots DCFC at SMUD HQ in Sacramento, billing is by kWh at a rate $0.22 per kWh plus a $0.35 usage fee at the end of charging. There is a 1 hour charging time limit. This is a great station and I really like what I see from Greenlots.

I found the Greenlots app and online site both give almost instant billing information whereas NRG eVgo only sends a once-a-month email with usage and billing info. I asked about this and I was told they are working on a better notification method.

 

[Nashco]

I think DCFC is too fast.

I hope you're kidding. "This electric car charges too fast" is something you'll never, ever hear me say. :lol:

Bryce

 

[SparkevBlogspot]

I think DCFC is too fast.

I hope you're kidding. "This electric car charges too fast" is something you'll never, ever hear me say.

Well, sort of tongue in cheek. I eat slow, and lunch time rush adds to slow restaurant service. If it took 1 hour, that would've been ok. But 20 minutes (sometimes 10 minutes) gets kind of annoying as I have to get back out there to manually disconnect and move the car. L2 is too slow even if SparkEV has 6.6 kW. Maybe L2.5 at about 12kW?

And yes, I have actually said "My car charges too fast!" Not being EV drivers, context was lost on them.