AC charging - fuses and efficiency

Hello Guys

I am investigating a charging solution for our apartment complex and in order to understand and be able to brief the attendents about this, I am currently looking at some things with AC charging.

1. On our Leaf we have the 3.3kW charger. That is 16 amps on 240Volts. What happens if I plug this in an outlet that has 240V and a 8 amp fuse? Will the car charge slower, or will the fuse go?

2. Regaring the efficiency.
According to this article: http://ecomento.com/guide/buying-a-nissan-leaf-read-this-guide/
The charge time on a 3.3kW charger on 240V is 8 hours
The charge time on a 6.6kW charger on 240V is 5 hours.

So with the 3.3kW charger drawing 26,4kWh in 8 hours, and putting 24kWh in the car, means that we lost 10%
But with the 6.6kW charger over 5 hours we draw 33kWh from the outlet, and deliver 24kWh in the car, which is a 37% loss.
Are these numbers correct? Maybe the article is missinformed. (Or my math is off)

Now I saw some mentions that the 3.3kW charger really takes 3.8kW from the outlet, and thus my starting numers could be off.

jonta said:

Hello Guys

I am investigating a charging solution for our apartment complex and in order to understand and be able to brief the attendents about this, I am currently looking at some things with AC charging.

1. On our Leaf we have the 3.3kW charger. That is 16 amps on 240Volts. What happens if I plug this in an outlet that has 240V and a 8 amp fuse? Will the car charge slower, or will the fuse go?

Click to expand...

If you had such an arrangement, you'd need to have the EVSE limit you to 8 amps, otherwise the the fuse or circuit breaker will blow/trip. I don't know of any 8 amp or less 208/240 volt EVSEs in the US. By NEC, it isn't allowed nor safe to have a continuous load at 100% of the circuit's rating either.

Re: EVSE, see http://support.openevse.com/support/solutions/articles/6000052074-basics-of-sae-j1772 and http://www.sae.org/smartgrid/chargingprimer.pdf. The pilot signal's duty cycle from the EVSE tells the car how much it can draw at max.

Browsing around at Clipper Creek's site, the lowest amperage 208/240 volt EVSE I can find is the LCS-15 at https://store.clippercreek.com/level2/level2-12-to-15. That's a 12 amp 208/240 volt EVSE and requires at 15+ amp circuit.

http://www.mynissanleaf.com/viewtopic.php?p=262630#p262630 may also help.

jonta said:

2. Regaring the efficiency.
According to this article: http://ecomento.com/guide/buying-a-nissan-leaf-read-this-guide/
The charge time on a 3.3kW charger on 240V is 8 hours
The charge time on a 6.6kW charger on 240V is 5 hours.

So with the 3.3kW charger drawing 26,4kWh in 8 hours, and putting 24kWh in the car, means that we lost 10%
But with the 6.6kW charger over 5 hours we draw 33kWh from the outlet, and deliver 24kWh in the car, which is a 37% loss.
Are these numbers correct? Maybe the article is missinformed. (Or my math is off)

Click to expand...

You can't calculate it this way. Also, not all 24 kWh of the battery is user accessible. There are only 21-22 kWh accessible on a new battery.

Also, the charging rate slows down as the battery gets closer to full. See chart at http://www.mynissanleaf.com/viewtopic.php?f=30&t=15009&start=30. And, for a '13+ with 6.x kW OBC, there's the slow down and bounce phase. See graph at http://www.mynissanleaf.com/viewtopic.php?p=338038#p338038.

Some .gov labs have done studies on the amount of charging loss/efficiency. See below:
https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf
https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2012Leaf.pdf

cwerdna said:

If you had such an arrangement, you'd need to have the EVSE limit you to 8 amps, otherwise the the fuse or circuit breaker will blow/trip. I don't know of any 8 amp or less 208/240 volt EVSEs in the US. By NEC, it isn't allowed nor safe to have a continuous load at 100% of the circuit's rating either.

Re: EVSE, see http://support.openevse.com/support/solutions/articles/6000052074-basics-of-sae-j1772 and http://www.sae.org/smartgrid/chargingprimer.pdf. The pilot signal's duty cycle from the EVSE tells the car how much it can draw at max.

Browsing around at Clipper Creek's site, the lowest amperage 208/240 volt EVSE I can find is the LCS-15 at https://store.clippercreek.com/level2/level2-12-to-15. That's a 12 amp 208/240 volt EVSE and requires at 15+ amp circuit.

http://www.mynissanleaf.com/viewtopic.php?p=262630#p262630 may also help.

Click to expand...

Ah, well in my case I was visiting my father, and tested to plug into his engine heater outlet. He said it was rated at 6 amps, and I connected the EVSE level 1 cable that came with the car. As far as I can see there is nothing I can do to limit anything with it.
So either it somehow charged at 6 amps, or the outlet was rated higher at 16 amps.

cwerdna said:

You can't calculate it this way. Also, not all 24 kWh of the battery is user accessible. There are only 21-22 kWh accessible on a new battery.

Also, the charging rate slows down as the battery gets closer to full. See chart at http://www.mynissanleaf.com/viewtopic.php?f=30&t=15009&start=30. And, for a '13+ with 6.x kW OBC, there's the slow down and bounce phase. See graph at http://www.mynissanleaf.com/viewtopic.php?p=338038#p338038.

Some .gov labs have done studies on the amount of charging loss/efficiency. See below:
https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf
https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2012Leaf.pdf

Click to expand...

[/quote]

Ah. I knew that the charge speed declined as the battery got fuller when you used DC charging, but not when doing AC charging as well.
The graphs from the thread was very useful, thanks!.
So has anyone measured the total kWh that was drawn from the outlet in order to charge the 24kWh car from 0-100%? (on 240V 16A)

jonta said:

Ah, well in my case I was visiting my father, and tested to plug into his engine heater outlet. He said it was rated at 6 amps, and I connected the EVSE level 1 cable that came with the car. As far as I can see there is nothing I can do to limit anything with it.
So either it somehow charged at 6 amps, or the outlet was rated higher at 16 amps.

Click to expand...

No. The stock L1 EVSE does not let you limit things. And, there's no UI in the car to limit how much it draws. The stock L1 EVSE will pull 12 amps @ 120 volts and you should be connected to a 15+ amp circuit.

1. You need an EVSE that you can turn down that far. Look at eMotorWerks. All of theirs will do it. You'd need to take it down to 6 amps to be under the 80% max for continuous load.

2. Charging at 240 volts is about 92% efficient.

Bear in mind the OP appears to be in Sweden with 230V sockets. My understanding is the "L1" plug provided with the Leaf operates at 230V and up to 12A in Europe. The 12A limit comes from the EVSE cord, not what the onboard charger is capable of.

Rob

^^^
The OP had no location information when I made my initial response and also may not have in my later responses.