Please help! Will L2 charger use less kwh/energy than the Trickle charge?!

Just bought our 2013 Nissan Leaf and pretty surprised it takes 21 hours with the trickle charge. Surprisingly I havent found the answer to this question online.. Since the L2 charger takes a fraction of the time to charge than the trickle charger does that make it cheaper to charge or is the L2 fast charger strickly just for convenience?

You have a fixed overhead for the cooling pumps and stuff. L2 charging still has the same overhead but as a percentage it is less. This makes L2 more efficient.

If you have the enhanced charger in your car ( it comes with fast DC charging) so if you have two connectors you can charge at 27.5A. otherwise it is 16A but it is still faster than 120V 12A.

My 2012 only had a 16A L2 charger and it worked out fine.

Just to clarify, and I know this doesn't effect the OP, the faster charger was only available on '13 and on Leafs, IOW a '12 even with QC port will still only max out at 16a@240v or 12a@120v

jjeff said:

Just to clarify, and I know this doesn't effect the OP, the faster charger was only available on '13 and on Leafs, IOW a '12 even with QC port will still only max out at 16a@240v or 12a@120v

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Good point, I was assuming everyone knew the 2012 Leaf only had a 16A charger. My 2012 dis have a QC port and a 16A charger

GlennD said:

jjeff said:

Just to clarify, and I know this doesn't effect the OP, the faster charger was only available on '13 and on Leafs, IOW a '12 even with QC port will still only max out at 16a@240v or 12a@120v

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Good point, I was assuming everyone knew the 2012 Leaf only had a 16A charger. My 2012 dis have a QC port and a 16A charger

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Yes I was quite confident you'd know and didn't want you thinking I was trying to correct you but I was just thinking about someone new to a Leaf or thinking about purchasing a used pre '13 thinking just because the Leaf had the QC port that it would have the upgraded 27.5a charger
I like lots of things better about my '13 vs my '12 and much faster L2 charge times is near the top of the list.

Seems to me from what I've read on this board that 2013 seems to be the sweet spot unless you are talking about the ones with the 30kwh batteries. Vs. the earlier ones, it has the better charger and the battery % display. Vs. the later ones, it has the long battery life mode to restrict charging to 80% while later ones you have to play with the timer to try to replicate that feature.

Am I right?

DarthPuppy said:

Seems to me from what I've read on this board that 2013 seems to be the sweet spot unless you are talking about the ones with the 30kwh batteries. Vs. the earlier ones, it has the better charger and the battery % display. Vs. the later ones, it has the long battery life mode to restrict charging to 80% while later ones you have to play with the timer to try to replicate that feature.

Am I right?

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Owning both I would sure say that statement is true In hindsight I sure wish I had waited around for a good deal on a '13 instead of purchasing my '12(which at the time was $2-3k less than a comparable '13). I now see '13's for about same or even less than I paid for the '12 7 months ago and other than the AC failure(fixed under warranty due to a faulty part) I can't really see a downside to the '13(or probably newer). I believe it's one of the reasons one sees so many more '12s priced so low. Not that the '12 is a bad car, just they made quite a few improvements in the '13 model year(and actually after 4/'13 for the better battery chemistry).

Seems to me there are two disparate questions - one in the subject and one in the body.

To answer the one in the subject line, not really. The trickle charge will trickle approx. 24KWh into your battery over a long time. The L2 charger (be it a 16A or 27.5A) will push that same 24KWh into the same battery, but faster. It's still 24KWh...but through a hose instead of through a straw.

There will be some minor savings, as mentioned above, because cooling pumps, etc, do not run as long during the shorter charge.

I don't know if you've already noted or not that the 21h estimate for the L1 charger is from 0% or close to it. Me personally (until my L2 arrives tomorrow) I usually arrive home with 30-70% left on my battery. Only the 30% really takes all night, and the last few hours of that is the slow jump from 98% to 100% while the BMS balances cells. You can count on a little over 5% per hour on L1. If you need faster turnaround then L2 is really worth it and doesn't use any more or less power.

The battery pack re-builder near me recommends occasional use of the L1 Charger since it does take longer which is better for the battery and he feels it does a better job of balancing the pack at the end of the cycle, He says he would see some folks less often if they used the L1 at least a few times a month.

GuitarESPplayer said:

Surprisingly I havent found the answer to this question online.. Since the L2 charger takes a fraction of the time to charge than the trickle charger does that make it cheaper to charge or is the L2 fast charger strickly just for convenience?

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Ingineer has measured the efficiency back in 2012:

L1: 78%
L2 (3.3kW): 91%
I estimate that L2 (6.0kW) achieves about 93%

Put another way, for every kWh that goes into the battery, here is how much electricity is wasted:

L1: 28% more wasted
L2 (3.3kW): 10% more wasted
L2 (6.0kW): 7.5% more wasted

So, L1 charging wastes almost 3X as much energy as L2 (3.3kW) charging and almost 4X as much energy as L2 (6.0kW) charging.

OTOH, starting with MY2013, the L2 charger can ramp down to very low power levels (600W) to allow for full cell balancing during a single charge cycle. This period at the end of the charge cycle will be less efficient than the faster portion of the charge, so if you want to maximize efficiency with L2, don't charge to full.

RegGuheert said:

GuitarESPplayer said:

Surprisingly I havent found the answer to this question online.. Since the L2 charger takes a fraction of the time to charge than the trickle charger does that make it cheaper to charge or is the L2 fast charger strickly just for convenience?

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Ingineer has measured the efficiency back in 2012:

L1: 78%
L2 (3.3kW): 91%
I estimate that L2 (6.0kW) achieves about 93%

Put another way, for every kWh that goes into the battery, here is how much electricity is wasted:

L1: 28% more wasted
L2 (3.3kW): 10% more wasted
L2 (6.0kW): 7.5% more wasted

So, L1 charging wastes almost 3X as much energy as L2 (3.3kW) charging and almost 4X as much energy as L2 (6.0kW) charging.

OTOH, starting with MY2013, the L2 charger can ramp down to very low power levels (600W) to allow for full cell balancing during a single charge cycle. This period at the end of the charge cycle will be less efficient than the faster portion of the charge, so if you want to maximize efficiency with L2, don't charge to full.

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So if I am reading this correctly the L1 in 2011/2012 did the balancing at around 80% which is what many recommend for longer battery life. Is this still true on 2013 and newer Leafs? The real cost is when the battery fails outside of warranty not the electricity to charge it so whats the best roll of the dice?

RockyNv said:

So if I am reading this correctly the L1 in 2011/2012 did the balancing at around 80% which is what many recommend for longer battery life. Is this still true on 2013 and newer Leafs?

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Active cell balancing of the LEAF battery pack occurs at all SOCs, regardless of whether it is charging or discharging. But balancing is more effective at very low charge/discharge rates since the shunts operate at about 1A.

RockyNv said:

The real cost is when the battery fails outside of warranty not the electricity to charge it so whats the best roll of the dice?

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Sure, but that the wear-out of the battery is a SEPARATE issue. There is no clear evidence whether choosing L1 versus L2 makes any difference one way or the other. Wasting energy certainly has a monetary cost, but it has other costs, as well.

FWiW, it takes less energy from the wall to charge the 2015 with 6 kW charger than the 2011 with 3.3 kW charger using the same 30-ampere, 240-volt AeroVironment EVSE and revenue accuracy meter because the faster charging results in less overhead loss.

Gerry

All things being the same, my understanding is that electrically (using electrical formulas) charging at 240 volt is more efficient and will cost much less than the LONGER time that the 120 volt charger. That is from the electrician who installed my 240 volt service in my garage.

My Level II charger is about 6x faster than the Level I. Before, I used to charge (at 120 volt) about 5% capacity of my 24KHW battery PER HOUR of charging. With 240 volt, I can charge 30% capacity per hour, which is an amazing improvement. I can charge the car from 40% to 100% in only 2 hours. In addition to the less cost, I would not give up my Level II charger FOR ANYTING!!

A 240 volt 30 amp device (7,200 watts) is potentially using 4 times as much energy as a 120 volt 15 amp device (1,800 watts). While 240 volts is indeed more efficient at turning a motor and such for battery charging the advantage is not as great. Your are consuming the wattage in either case with the greatest saving being time and maybe the cost of a running a few low draw fans along with the coolant pump when it cycles. A 240 volt 40 amp device (9,600 watts) should be able to charge 6 times faster since it is basically capable of consuming about 6 times more power than a 120 volt 15 amp device. Actual energy savings at the end of the month for some folks could end up being measured in pennies though not dollars. You might see a modest savings from using an L2 at home but I would not expect massive savings that would pay for the cost of installation unless you are an extremely high mileage driver. The biggest savings would be time and convenience.

For me since I convinced my employer to go green the biggest savings come from being able to charge for free using one of the L2 charging stations at work. The L1 will probably still see occasional use to give the batteries a kinder maintenance charge in the hopes of extending their life.

I may put an amp probe on my 120 volt charger to see what the actual amperage draw is the next time I use it however that might not be for a few weeks.

I have not built a power supply/charger or phase converter in almost 45 years so I am quite a bit rusty, After a crippling accident I had to switch gears and now write analytical software.

My back-of-the-napkin calculation for a full recharge of a 30kWh LEAF (27.5 kWh usable on mine) shows the L2 charging session saves me about 5.6 kWh of electricity vs L1 "trickle charging". I pay 10 cents per kWh here, so 56 cents.

Pencil it out further, and my $600 L2 EVSE would be break-even at 120k miles.

Don't forget the 30% Federal tax credit for installation of clean vehicle refueling equipment in your home, which would include EVSE equipment and installation cost, I believe. Local incentives are sometimes available to help fund that, as well. Check with your city/county/state revenue departments and electricity provider.

Another factor to consider with shorter charge times on L2, the coolant pumps run for a shorter time which in theory would extend their service life.

RockyNv said:

A 240 volt 30 amp device (7,200 watts) is potentially using 4 times as much energy as a 120 volt 15 amp device (1,800 watts).

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You can't make any such claim, just on the basis of power consumption. All you can say is that the 7200W device is consuming energy four times FASTER than the 1800W one. If it only runs one fifth as long, then it uses LESS energy. "Potentially", even a 100Watt device can use more energy, given time.

Levenkay said:

RockyNv said:

A 240 volt 30 amp device (7,200 watts) is potentially using 4 times as much energy as a 120 volt 15 amp device (1,800 watts).

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You can't make any such claim, just on the basis of power consumption. All you can say is that the 7200W device is consuming energy four times FASTER than the 1800W one. If it only runs one fifth as long, then it uses LESS energy. "Potentially", even a 100Watt device can use more energy, given time.

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I was only pointing out that the claims that these devices save money because they can charge four to six times faster is a bit moot since they are also capable of consuming four to six times more electricity per hour as the L1 making the savings not as great or earth shattering as some may believe that they will be. 1.875 hours at 9,600w, 2.5 hours at 7,200w or 10 hours at 1,800w is all basically 18 kw keeping the math simple. Yes there are some variations during the balancing cycle where things taper off but we are still taking about consuming about 18 kw more or less with either of the three chargers. I would really hate to have folks investing in the L2s based on the impression that they are going to save enough money to pay off the expense in short time. Do it for the convenience yes but don't go in thinking you are guaranteed to save massive amounts of money on electricity using an L2 instead of an L1 and that the savings is going to pay for the install in short time.

kW and kWh are very different metrics. It's the same as confusing gallons with horsepower. Think of kW = horsepower, kWh = gallons.

If one charges at 1 kW (or 1000 watts) for 6 hours, 6 kWh came out of the wall. If it's at 6 kW for 1 hour, it's also 6 kWh. If it's 1 watt for 6000 hours, it's also 6 kWh.

The below have charging efficiency tests of the '12 and '15 Leafs. They have different OBCs).

https://avt.inl.gov/pdf/fsev/SteadyStateLoadCharacterization2012Leaf.pdf
https://avt.inl.gov/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf

Looks like the '15 took a step backwards in 120 volt charging efficiency.

'11 and '12 have the same OBCs. '13 and beyond have a different design that's under the hood instead of under the hump in the back of the car and there are at least 2 different OBC choices on the '13 (3.x kW and 6.x kW).

From a given starting state of charge to desired SoC will by definition require more energy out of the wall at 120 volts than 208 or 240 volts due to worse charge efficiency at the lower voltages. So, to answer the question in the title, yes.

cwerdna said:

The below have charging efficiency tests of the '12 and '15 Leafs. They have different OBCs).

https://avt.inl.gov/pdf/fsev/SteadyStateLoadCharacterization2012Leaf.pdf
https://avt.inl.gov/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf

Looks like the '15 took a step backwards in 120 volt charging efficiency.

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Actually, it looks like the measurements made on the MY2012 LEAF are not accurate. Specifically, it appears they did not include the pumps in the MY2012 measurements. Compare them to the measurements made by Ingineer and you will see that the MY2015 measurements come much closer to reality.

cwerdna said:

From a given starting state of charge to desired SoC will by definition require more energy out of the wall at 120 volts than 208 or 240 volts due to worse charge efficiency at the lower voltages.

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Sorry, but you cannot make such a blanket statement about efficiency versus output voltage without knowing details about the power converter. Some are more efficient at lower output voltages while others are more efficient at higher output voltages.

The answer to OP's question was clearly stated in the very first response given by GlennD:

GlennD said:

You have a fixed overhead for the cooling pumps and stuff. L2 charging still has the same overhead but as a percentage it is less. This makes L2 more efficient.

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All other effects are minor by comparison.