L2 vs L1...time and money...charging wise which is cheaper?

[tjw]

I have using just the standard 110v that came with the car. The question is 220/3hrs vs 110/9hrs. I have al leaf s with 6.6kw charger and what would be the difference cost and time wise between the two?

 

[TomT]

L1 is less efficient than L2 since the parasitic losses are a constant.

I have using just the standard 110v that came with the car. The question is 220/3hrs vs 110/9hrs. I have al leaf s with 6.6kw charger and what would be the difference cost and time wise between the two?

 

[davewill]

The time difference is on the order of 6-7x. A 0-100% charge at 120v is supposed to be 21hrs and at 6kW approx 3-4 hrs. The cost difference is basically free for the 120v vs. the install cost of the L2 EVSE at your house...which could be anywhere from $400-$4000 depending on your circumstances. There's a small difference in the electricity cost, because 240v charging is more efficient, but the dollar cost of that difference is so low compared to the installation cost that it just doesn't matter.

In reality, the time difference only matters if you need quick turnaround at home...like driving half the day, plugging in at home and then heading back out that evening. Otherwise it is of no import. If you can cover your daily driving overnight using 120v, then you may well decide to stick with it.

It's really a matter of convenience and function more than $. Either you need/want the faster charging enough to pay for the install, or you don't.

 

[planet4ever]

L1 charges at a rate of about 1.1kW, so your 9 hours would imply putting in about 8kWh of electricity. The 3:1 ratio you mention applies to 16 amp 240 volt charging. That wouldn't be your case unless you got a 16A EVSE. Your LEAF with the "6.6kW" charger can really charge the battery at a rate of about 6.0kW. Nissan has tried to inflate the number by quoting how much power it draws from the wall rather than how much it delivers to the battery. So putting 8kWh of electricity into the battery at a rate of 6kW would in theory take only 8/6 = 1.33 hours! In practice there are restrictions on that. If you are charging the battery to 100% the charging rate slows down as the battery gets close to full. And a really big restriction is the one I mentioned above. You can't charge any faster than the charger (built into the car) will support, but you also can't charge any faster than the EVSE (on the wall, or part of your charging cord) will allow.

As for which is cheaper, TomT answered that. As a rough approximation you can assume that 120v charging is about 75% efficient, while 240v charging is about 85% to 90% efficient. So to get that 8kWh of electricity into the battery you need to buy about 10.3kWh from your utility when charging at 120v, but only about 8.9 to 9.4kWh if charging at 240v.

By the way, you probably noticed that I kept saying 120v and 240v while you were saying 110v and 220v. The Japanese seem to believe Americans have 110/220, so that's what they use for all their documentation. Many Americans also believe that, even though our standard changed to 120/240 more than half a century ago. If you don't believe me, try (carefully!) sticking the probes of an inexpensive voltmeter into an outlet in your house. In fact I just now tried it myself, and read 119.6v.

Ray

 

[smkettner]

I only get six hours of lowest TOU electric rates.... L2 is way less $$ for me.

 

[EddyKilowatt]

As a rough approximation you can assume that 120v charging is about 75% efficient, while 240v charging is about 85% to 90% efficient. So to get that 8kWh of electricity into the battery you need to buy about 10.3kWh from your utility when charging at 120v, but only about 8.9 to 9.4kWh if charging at 240v.

Ray

Interesting. Is the efficiency loss because the 120V has to go through a boost converter (or some other additional processing step) to charge the ~400V battery? Or is it because there's some fixed ~100W overhead to run the charge system, and the slower 120V charge incurs that overhead for much longer?

I thought I'd 'been doing good' by intercalating my lithium ions nice and slow at the 1.2 kW charge rate... and perhaps that's how the batteries are happiest... but I hadn't considered charger efficiency.

I've been planning on at least the EVSE Upgrade and 2.4 kW charging, so I can get 'er done within the off-peak window (once I get that tariff applied), so this is all kind of moot... I'm just interested to learn what the actual loss mechanism is when the car is charging.

 

[dgpcolorado]

Interesting. Is the efficiency loss because the 120V has to go through a boost converter (or some other additional processing step) to charge the ~400V battery? Or is it because there's some fixed ~100W overhead to run the charge system, and the slower 120V charge incurs that overhead for much longer?

I thought I'd 'been doing good' by intercalating my lithium ions nice and slow at the 1.2 kW charge rate... and perhaps that's how the batteries are happiest... but I hadn't considered charger efficiency.

I've been planning on at least the EVSE Upgrade and 2.4 kW charging, so I can get 'er done within the off-peak window (once I get that tariff applied), so this is all kind of moot... I'm just interested to learn what the actual loss mechanism is when the car is charging.

As you surmised, it is because there is a fixed overhead to run the cooling pumps and charging system. Longer charge time means more wasted electricity from the overhead.

By the way, if you charge to 80% rather than 100% you will get better charge efficiency because the charge rate tapers at it nears 100%. It is only a few percent but it is measurable for those of us who have wall meters.

 

[planet4ever]

Interesting. Is the efficiency loss because the 120V has to go through a boost converter (or some other additional processing step) to charge the ~400V battery? Or is it because there's some fixed ~100W overhead to run the charge system, and the slower 120V charge incurs that overhead for much longer?

I thought I'd 'been doing good' by intercalating my lithium ions nice and slow at the 1.2 kW charge rate... and perhaps that's how the batteries are happiest... but I hadn't considered charger efficiency.

As you surmised, it is because there is a fixed overhead to run the cooling pumps and charging system.

As dgpcolorado said, it's fixed overhead. The on-board charger (though not the battery) is water cooled, so the cooling pump runs during charging. The coolant then goes through a radiator where a radiator fan runs at least part of the time. Both the pump and the fan are powered by 12v, and draining the 12v battery for up to 20 hours wouldn't work, so a DC/DC converter is also running that pulls electricity out of the traction battery, reducing the effective amount being added to it. But that's not the end of the story, because the DC/DC converter also generates enough heat that it, too, is water cooled, putting more load on the cooling system.

On the charge rate, even a 6kW rate is low compared with the battery capacity, so doesn't put any strain on the battery. Quick Charge, on the other hand, can be somewhat high. The battery experts like to work in C ratings, and say that anything under 1C is no problem. QC is up to 2C, while 6kW is 0.25C.

Ray

 

[DaveinOlyWA]

The time difference is on the order of 6-7x. A 0-100% charge at 120v is supposed to be 21hrs and at 6kW approx 3-4 hrs. The cost difference is basically free for the 120v vs. the install cost of the L2 EVSE at your house...which could be anywhere from $400-$4000 depending on your circumstances. There's a small difference in the electricity cost, because 240v charging is more efficient, but the dollar cost of that difference is so low compared to the installation cost that it just doesn't matter.

In reality, the time difference only matters if you need quick turnaround at home...like driving half the day, plugging in at home and then heading back out that evening. Otherwise it is of no import. If you can cover your daily driving overnight using 120v, then you may well decide to stick with it.

It's really a matter of convenience and function more than $. Either you need/want the faster charging enough to pay for the install, or you don't.

"quick turnaround??"

fact of the matter is that you CANT turn around on 120 volts if you drive more than about 50 miles a day

120 means you really cant drive the LEAF for anything other than your commute unless your commute is pretty short. There are a lot of people that use only 120 volts but they are the exception and you would really have to examine your situation to evaluate whether you are ok with your car being essentially unusable a lot of the times.

Don't get me wrong; you dont tell us enough to really give you specific advice but 120 could work for you but odds are, it wont

 

[thait84]

I drive about 60 miles a day and I have used the standard 120v EVSE for about a year now. Maybe once a week or so, I will "top off" at an L2 EVSE like chargepoint for 45min to an hour or so.

I would have gotten the L2 EVSE at home long ago, but my electric panel is on the opposite side of the house in relation to the garage, so I will have a 100 ft cable run....

 

[planet4ever]

I drive about 60 miles a day and I have used the standard 120v EVSE for about a year now. Maybe once a week or so, I will "top off" at an L2 EVSE like chargepoint for 45min to an hour or so.

Hmmm ... If you use the car only for commuting and work 5 days a week, that's 300 miles a week. The L2 top off might give you 10miles, 15 miles at the most. You are either a dedicated hypermiler or you must be charging about 70-75 hours a week. I guess that's feasible if you are charging much of the weekend.

If you really mean 60 miles a day as in 420 miles a week, I don't see how you can do it unless you charge at work. That would presumably require about 13 hours charging per night even allowing for your top off. Do tell us more.

Ray

 

[DaveinOlyWA]

When I got my LEAF, what I could not do was the Centrailia trip two days in a row. Back then there was no charging options other than home and it was 63 miles round trip on a 10 hour shift. So guessing its that extra few hours that did it but getting home and plugging it in immediately it usually had no more than 9-10 bars when it would have gone back to Centrailia.

Now, what we did was Centrailia every once in a while and my commute the rest of the time which was about 10 miles at the time. Because I left MUCH earlier, it usually only had 5-6 bars when I left at 5:30 AM after being plugged in about 9ish PM the night before.

Either way, its a 10% efficiency penalty using 120 as well. considering all that, it simply is not worth it. I would get the EVSE upgrade as a cheap option