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Charging to 80% using car's end timer plus EVSE timer

Posted: Fri May 11, 2018 11:44 am
by wch
I posted this on reddit earlier today. I apologize for cross-posting, but I realized that there are more experts on this forum and wanted it to get feedback from the people here. Here it is with some edits:

I just realized that it should be possible to limit charging to 80% by using the car's end timer together with the charging station's timer, if you have a smart one. I have a Juicebox, which lets me set limits on the charging time.

Here's the idea: If I set the car's end timer to (say) 8:00 AM, it will try to time the charging so that it reaches 100% at 8AM. Then I configure the EVSE to stop at 2 hours before that, at 6:00 AM. I think that should stop it at about 80% each day, without having to fiddle with timers.

The times are just an estimate -- I haven't tried this yet, and so it might need some experimentation to confirm. (I have a 30kWh model, and the Juicebox can max out the 6.6.kW charger in the car.)

I also suspect the temperature also matters. I just looked at some of the charging data from the Juicebox, and I think that the charging taper at the end is longer in cold weather and shorter in warm weather. So the 2 hour gap might need to be longer in the winter, and shorter in the summer.

Has anyone out there tried doing this? Any thoughts on whether this will work?

https://www.reddit.com/r/leaf/comments/ ... imer_plus/

Re: Charging to 80% using car's end timer plus EVSE timer

Posted: Fri May 11, 2018 11:46 am
by LeftieBiker
Don't expect to hit 80% exactly, but it should work as far as I can see. It's a shame that timers aren't one of the features of most EVSEs...

Re: Charging to 80% using car's end timer plus EVSE timer

Posted: Sun May 13, 2018 11:51 am
by RichCapeCod
LeftieBiker wrote:Don't expect to hit 80% exactly, but it should work as far as I can see. It's a shame that timers aren't one of the features of most EVSEs...
Yes, I agree. It's such a basic need for the owner to control distance to be traveled with battery life considerations. My understanding is, when such a limiter is put in an EV it somehow detracts from the ability to claim maximum range. Not sure if that's accurate.

Rich

Re: Charging to 80% using car's end timer plus EVSE timer

Posted: Sun May 13, 2018 11:55 am
by LeftieBiker
The EPA dinged Nisan for their 80% "Long Life" charge limiter in 2013, and it apparently scarred them for life, the way they have behaved since. GM calls their charge limiter "Hilltop Mode" and it's been fine for them. All Nissan has to do is call it something like "Max Regen Mode" and that would be fine. But NO, not Nissan...

Re: Charging to 80% using car's end timer plus EVSE timer

Posted: Mon Jun 11, 2018 9:17 am
by ldallan
wch wrote:The times are just an estimate -- I haven't tried this yet, and so it might need some experimentation to confirm. (I have a 30kWh model, and the Juicebox can max out the 6.6.kW charger in the car.)
I'm curious how this has been working for you. Satisfactory?

We've got the 2015 Leaf "S" model 24 kWh without CarWings/NissanConnect. For a while, I was using the built-in charging timer capability with "Stop at HH:MM", but found it to be lame / kludgy and not worth the hassle. Sigh. Bummer. (or operator error on my part?)

IIRC, the issue was the estimated time to charge at a Level-2 6.6 kW charging station was grossly conservative with excessive HH:MM expected.

I would have to calculate when the car thought it would get to 80% or 90% ... generally way off by an hour or more ... and then make an error-prone adjustment of how long it would really take.

FWIW:
There are four ChargePoint charging stations in our city, each with dual charging heads. I use them quite a bit by coordinating with errands I can walk to. Their ChargePoint smart-phone app is handy to track how the charging is proceeding, and then remotely stopping the charge when I figure it is getting to the 80% to 90% target SOC.

I'm checking if LeafSpy can do something like the equivalent of that.
http://www.mynissanleaf.com/viewtopic.php?f=31&t=25989

Re: Charging to 80% using car's end timer plus EVSE timer

Posted: Sat Jun 16, 2018 1:28 pm
by wch
ldallan wrote: I'm curious how this has been working for you. Satisfactory?
tl;dr: I set the EVSE's stop timer to be 3 hours earlier than the car's end timer and have ended up with charge of around 75-85%. This is with a 2016 SL with 30kWh battery and a charger capable of 6.6kW.

I have only actually tested it with perhaps 5 or 6 charges. I had to fiddle around a bit with the timing, and here's what I found:
  • The car starts charging earlier than is strictly necessary to finish at the specified end time. For example, with the end timer set for 8 AM, it would often finish at 6:30. (This is before I started using a timer on the charging station.)
  • When just an end timer is set, the car seems to always start charging on the hour or half hour -- that is with :00 or :30 on the clock. Because the minimum increment is a half hour, this must limit the precision with which you can hit a desired charge using timers alone.
  • I have the end timer set to 8:00 AM, and when the car has a 60-70% SoC, it often start charging at around 4 or 4:30. To end up with a ~80% SoC, I set the charger's stop time to 5:00 AM. I think it usually ends up between 75% - 85%, but I haven't tested enough times to be sure.
Again, I haven't done this enough times to get good data. We don't drive that much in general, and on weekends we charge it to 100% because we do more driving; after it's charged to 100%, it takes a few weekdays for us to bring it down below 80%, so there's just 2-3 days each week where we can test out this charging strategy. If you try it out, please let us know what you discover!

Re: Charging to 80% using car's end timer plus EVSE timer

Posted: Thu Jun 28, 2018 9:29 am
by specialgreen
If I set my 2017 Leaf S to stop charging for 2pm, 6 hours AFTER my 8am daily commute departure, then the LEAF is usually 75%-85% charged when I unplug and drive off. This is basically the same as WCH's comment, except it takes my 2.88kw EVSE twice as long to charge the LEAF. I think the state of charge at 8am varies, depending especially on whether the car was charging all the way from 20% or just from 70%.

You may need to experiment to find the right number of hours for your LEAF/EVSE/weather. Also, if you really _need_ 80%, then you may need to put-up with seeing 90%+ some mornings.