Bang-for-your-buck Charging?

[treinjapan]

I'm sure this has been discussed before, but I don't even know how to search for it.

It seems that while charging the Leaf at home (200V in Japan, takes 8 hours 0-100%), the "top" 20% of the battery takes the longest to charge. Is this true, or am I just imagining it?

Our house has a readout telling us how many KWs we are using at any time. When we plug the Leaf in, it jumps up 2KWs. On a normal day pre-Leaf, we usually used about 8-9 KW per day, but now we are using much more obviously. Our rate is roughly 27 yen per KW, not including solar panel input. We have a 4 KW panel array but the sun isn't exactly melting our faces yet, up here in Northern Japan.

So if it's true that the last 20% of the battery takes longer to fill, doesn't that mean that it's the worst bang-for-your-buck?

Side Note: It apparently takes a couple of weeks for Nissan to initiate CarWings for a used Leaf, so timed charging to 80% isn't a reality for us yet. Additionally, we park in a carport with the power cable and outlet outdoors. I'm a bit paranoid about getting it stolen, so I'm just charging a couple hours a day here and there when I'm around the house.

 

[mbender]

I'm certainly no expert and charge mostly at 110, but if it does slow down for you at 220, it's because it's drawing less current and therefore you are paying proportionately less. So "money-wise", you are getting no more and no less "beng-for-your-yen" , but "time-wise" yes, it may be taking longer to get the last 20% than any of the previous 20%s.

Now, it is also possible (and others here will likely chime in) that the efficiency of the EVSE diminishes as the current being drawn goes down, in which case you would be paying a little more per usable kWh transferred from the socket to the battery. But that's likely to be only a few % and doesn't sound like what your concern was.

Note that you pay (I assume) per kilowatt-hour or kWh, not per kilowatt or kW, as you indicated below. It's possible that it was just a typo (even the savviest of engineers here do it occasionally), but if not it may be the source of some of your (and others') confusion.

 

[RonDawg]

Yes it is true that charging, especially quick charging, will slow down as the battery reaches 100%. That is to protect the battery. At what point past 80% it slows down, I don't know.

As already mentioned above, if you are paying by the kWH, I don't think it would matter unless you are on a Time of Use plan and the slowed charging rate will cause you to extend into a more expensive time period. Or, if you are paying by the hour for charging, as opposed to by the kWH.

BTW CarWings is not involved in enabling Long Life Mode (80%), at least for North American Leafs. It's enabled via the Charge Timers on the nav system cars, and for the Leaf S it's done via the dash buttons on the far left side (far right side for RHD models). CarWings only allows remote charge start (if plugged in), remote manual turn on of climate control, and to see how much charge the battery has.

 

[EVDRIVER]

I'm sure this has been discussed before, but I don't even know how to search for it.

It seems that while charging the Leaf at home (200V in Japan, takes 8 hours 0-100%), the "top" 20% of the battery takes the longest to charge. Is this true, or am I just imagining it?

Our house has a readout telling us how many KWs we are using at any time. When we plug the Leaf in, it jumps up 2KWs. On a normal day pre-Leaf, we usually used about 8-9 KW per day, but now we are using much more obviously. Our rate is roughly 27 yen per KW, not including solar panel input. We have a 4 KW panel array but the sun isn't exactly melting our faces yet, up here in Northern Japan.

So if it's true that the last 20% of the battery takes longer to fill, doesn't that mean that it's the worst bang-for-your-buck?

Side Note: It apparently takes a couple of weeks for Nissan to initiate CarWings for a used Leaf, so timed charging to 80% isn't a reality for us yet. Additionally, we park in a carport with the power cable and outlet outdoors. I'm a bit paranoid about getting it stolen, so I'm just charging a couple hours a day here and there when I'm around the house.

The last portion of the charge takes longer because there is less current draw. It is less efficient because of the longer run time of the parasitic loads like cooling pumps, etc. Since you are on 200v you are already more efficient early in the charge cycle than 120v as a result of the time factor. The LEAF at the end of the charge cycle will run under 1A at times during the final charge.

 

[DNAinaGoodWay]

There is cell balancing going on as it tapers down to 100%. So, you should do that at least once a month.

There are ways to lock the cord to deter theft, try the search function.