Comparing kw charge vs. kw pay

[VonSpark]

Ever since I've leased my EV Spark, I have been looking at how much I was charge from the Utility. I was hoping if anyone here can enlighten me.

Yesterday was the first day that I drained my Spark to 5 miles left. Full tank is about 21kw so let say I have 2kw left on my battery. We also have chevy Volt which was drained to 0kw left.

Spark 2kw left and need total 19kw
Volt 0kw left and need total 16kw

19+16=35kw will be charge from 5/15 8pm evening to 5/16 2am morning.
One charger TurboCord for the (Volt) and the other Clipper Creek LCS-25P for the (Spark). Both charger are on 240v.

See picture below

Note: Orange is Solar products and blue is electricity draw from utility.

I am counting the blue bar from 8pm to 2am that is only 22kw was charge for both car. Did I stated that I needed 35kw for both car?

My questions is can anyone explain. I'm not complaining it takes 22kw of charging for 35kw on both car.

Thanks in advance.

 

[cwerdna]

First off, you need to get your units straight. It seems in all cases below, when you saw "kw", you actually mean kWh. See http://evseupgrade.com/?main_page=faq_info&faqs_id=26.

Also, your "chargers" aren't chargers, they're EVSEs. See http://www.mynissanleaf.com/viewtopic.php?p=332668#p332668 and http://www.mynissanleaf.com/viewtopic.php?p=262630#p262630. For L1 and L2 AC charging over J1772, the charger is on-board the car. The TurboCord and LCS-25P are both EVSEs.

Yesterday was the first day that I drained my Spark to 5 miles left. Full tank is about 21kw so let say I have 2kw left on my battery. We also have chevy Volt which was drained to 0kw left.

Spark 2kw left and need total 19kw
Volt 0kw left and need total 16kw

19+16=35kw will be charge from 5/15 8pm evening to 5/16 2am morning.
One charger TurboCord for the (Volt) and the other Clipper Creek LCS-25P for the (Spark). Both charger are on 240v.
...

http://gm-volt.com/2013/08/02/spark-ev-versus-volt-battery/ says the Spark EV has 17.3 kWh usable. Volt has 10.8 kWh usable (I believe it was a bit lower on earlier Volts). I believe the figures are right to within 1 or 2 kWh. If someone has better figures, please correct me.

But, charging even at 240 volts isn't 100% efficient as there are charging losses beside the overhead needed to run pumps and possibly fans. So, not all the electricity coming out of the wall makes it into the battery I unfortunately don't know the figure for either Chevy. Some Leafs figures are at http://www.mynissanleaf.com/viewtopic.php?p=333389#p333389

How do you know the Spark EV had 2 kW left? Does the Spark EV tell you that?

I roughly added up the blue bars in the timespan you mentioned and arrived at ~26 kWh. Do you have something w/more precision like actual numerical values of kWh at each hour instead of having to estimate from graphs?

 

[xylhim]

The explanation is that electric vehciles do not allow you to use the full capacity of their battery packs. For the Spark, you can only use about 17KWhr of it's pack, for the Volt, I think its somewhere between 10 and 12 useable. So really, you never completely drain your battery, if you did, you'd be causing damage to the cells.

 

[VonSpark]

How do you know the Spark EV had 2 kW left? Does the Spark EV tell you that?

I roughly added up the blue bars in the timespan you mentioned and arrived at ~26 kWh. Do you have something w/more precision like actual numerical values of kWh at each hour instead of having to estimate from graphs?

How do you know the Spark EV had 2 kW left? Does the Spark EV tell you that? I don't. That is why I am trying to figure out. My Spark stated that I only have 5 miles left. So I minus from the 21khw.

I roughly added up the blue bars in the timespan you mentioned and arrived at ~26 kWh? from 8pm to 2am other items in my home is using power. If you minus that it should be around 22kwh.

Do you have something w/more precision like actual numerical values of kWh at each hour instead of having to estimate from graphs? I wish I did. The only thing I can go by is the consumption meter which tell me how much electricity is being use. in hourly or half an hour.

 

[VonSpark]

The explanation is that electric vehciles do not allow you to use the full capacity of their battery packs. For the Spark, you can only use about 17KWhr of it's pack, for the Volt, I think its somewhere between 10 and 12 useable. So really, you never completely drain your battery, if you did, you'd be causing damage to the cells.

If what you said is true then 17x5miles is about 80miles range i have been avg.

So, 17 for the Spark and 10 for the Volt that is 27kwh was needed to charge both car. I calculated my charging between 8pm-2am is still about 22kwh. What these new number it looks really close.

Thanks for your input.

 

[cwerdna]

So, 17 for the Spark and 10 for the Volt that is 27kwh was needed to charge both car..

No, those are the roughly the usable battery capacities, assuming the battery is completely dead (or at least as dead as the car will let you take it).

As I said, charging isn't 100% efficient. If you pull 27 kWh out of the wall, not all of it makes it into the battery. Some is lost from having to run pumps, fans and from other resistive losses inside the on-board charger, battery, wiring, etc. Battery thermal management doesn't come for free either.

 

[nozferatu]

So, 17 for the Spark and 10 for the Volt that is 27kwh was needed to charge both car..

No, those are the roughly the usable battery capacities, assuming the battery is completely dead (or at least as dead as the car will let you take it).

As I said, charging isn't 100% efficient. If you pull 27 kWh out of the wall, not all of it makes it into the battery. Some is lost from having to run pumps, fans and from other resistive losses inside the on-board charger, battery, wiring, etc. Battery thermal management doesn't come for free either.

Funny thing is I've never ever seen my battery conditioning percentage move from 0%. Not even on the hottest of days.

 

[sspeedracer]

Isn't rate for PG&E lowest 11pm to 7am? Or does solar effect off peak savings? Curious as I am a SCE customer.

http://www.pge.com/web/includes/images/myhome/environment/whatyoucando/electricdrivevehicles/rateoptions/450x177_Winter-EV-Hours.jpg

 

[cwerdna]

Isn't rate for PG&E lowest 11pm to 7am? Or does solar effect off peak savings? Curious as I am a SCE customer.

http://www.pge.com/web/includes/images/myhome/environment/whatyoucando/electricdrivevehicles/rateoptions/450x177_Winter-EV-Hours.jpg

Depends on the schedule you're on, time of year and day.

http://www.pge.com/about/rates/rateinfo/rateoptions/daylightsaving.shtml

I'm on E-6 Smart. See E-6 PDF at http://www.pge.com/tariffs/ERS.SHTML. Of course, one could be on a non-TOU schedule like E-1.

I can't speak to solar and net metering.

 

[VonSpark]

Isn't rate for PG&E lowest 11pm to 7am? Or does solar effect off peak savings? Curious as I am a SCE customer.

http://www.pge.com/web/includes/images/myhome/environment/whatyoucando/electricdrivevehicles/rateoptions/450x177_Winter-EV-Hours.jpg

I am on an E-6 TOU with solar. Summer is May-Oct. Peak is Monday-Friday 1pm-7pm. That is why solar better to place it on 180 degree (south) to 250 degree (west). You sale unused kwh that you produce while you are at work.

I charge my Spark after 7pm until morning at a lower rates (off-peak)

 

[sspeedracer]

That is why solar better to place it on 180 degree (south) to 250 degree (west). You sale unused kwh that you produce while you are at work.

Brilliant

 

[Sesamecrunch]

I charge my Spark after 7pm until morning at a lower rates (off-peak)

Actually, I believe off-peak starts at 9pm on weeknights in Summer with E-6.