Todd1561
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Joined: Sun Sep 29, 2019 5:24 pm
Delivery Date: 30 Sep 2019

Charger current drop past 80% SOC

Sun Sep 29, 2019 5:39 pm

Hi everyone,

I’m a new Leaf owner, just bought a 2019 SV a few weeks ago. I’ve installed the stock Nissan L2 charger in my garage that came with the car and have been looking for an easy way to stop charging at 80%. I came across some anecdotal comments that the charger should start drawing less current around the 80% mark and therefore that could be detected and acted on accordingly. I’m very familiar with Arduinos, coding and some light electronics work so it seemed like something I could handle. So I tested my charger today with my clamp on ammeter and from 50% to 91% SOC it was always pulling ~27.5 amps the entire time. I was expecting to see a several amp drop but alas there was none. I stopped charging at 91% as this seemed to be a non-starter.

So my question... is anyone familiar with the “tapering off” these chargers are supposed to do, if any? The only drop I saw was a couple hundred milliamperes while in the low 80’s but that went up again after several minutes.

If this doesn’t work I may go back to my idea of integrating with the carwings API, but I was hoping to avoid that as it seems unreliable at best.

Thanks!

LeftieBiker
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 6:36 pm

As I understand it, the 80% tapering only occurs with DCFC stations, not L-1 and L-2 stations, and the station determines when it should happen, not the onboard charger, which isn't used in DC fast charging. There is some tapering on L-1/L-2 charging, but as you found, it happens in the nineties state of charge range.

Someone correct me if I'm mistaken.
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Kev994
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 6:43 pm

My 2016 ramps down at ~80%. I have a 32 amp ChargePoint and the charger’s graph shows a pretty steep decline that looks to start at around 80%. If you were using a 16 amp charger you wouldn’t see it until later.
2016 SL Coulis Red

cwerdna
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 7:08 pm

Todd1561 wrote:
Sun Sep 29, 2019 5:39 pm
So I tested my charger today with my clamp on ammeter and from 50% to 91% SOC it was always pulling ~27.5 amps the entire time. I was expecting to see a several amp drop but alas there was none.
Sounds right.
Kev994 wrote:
Sun Sep 29, 2019 6:43 pm
My 2016 ramps down at ~80%. I have a 32 amp ChargePoint and the charger’s graph shows a pretty steep decline that looks to start at around 80%. If you were using a 16 amp charger you wouldn’t see it until later.
You sure it's happening at 80% on the dash display? On my current and former '13 (obviously only 24 kWh), the L2 ramp down never happens until the car's in the 90ish% on the dash display... more like 94+%.

I've plugged in plenty of other Leafs at work, including '18+ Leafs (we have some of every model year) and I've observed similar behavior of not much energy making it into the battery in the last hour or so due to ramp down and bounces. See viewtopic.php?p=521788#p521788 for an example.

Here was one of my graphs of this. Took me awhile to find it: viewtopic.php?p=490435#p490435.

At work, we have 30 amp EVSEs and our supply voltage is around 208 volts. Next time you can see the ramp down, power up your car and look at the dash display's % SoC. I can almost guarantee you that it'll be above 90%.

If I turn on my 80% limiter via midnight to midnight 80% timer (yes, it's gone on US '14+ Leafs), let it charge to 80%, it's full power the whole time until the abrupt drop at 80%. If I then via NissanConenct/Carwings app tell it to charge now, it'll charge at full power for at least 30 maybe 30 to 45 minutes before beginning ramping down followed by the 2 or 3 bounces.

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LeftieBiker
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 7:18 pm

Well, I guess that clears THAT up! :roll: Maybe they changed the charging algorithm with the 30kwh pack...
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cwerdna
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 7:43 pm

LeftieBiker wrote:
Sun Sep 29, 2019 7:18 pm
Well, I guess that clears THAT up! :roll: Maybe they changed the charging algorithm with the 30kwh pack...
I don't think so. I'm pretty sure I've plugged in some 30 kWh Leafs (we have a bunch) at work judging by how much juice they drew. Drivers are supposed to put in the model year of their car in the registry but it's not like I go around checking before plugging them in. I have no reason. If I'm out at our stations, there are finished cars and waiting ones, I plug them in and start a session for them.

I don't think Kev994 is correct about his ramp down starting at ~80%. It's got to be higher.
Last edited by cwerdna on Sun Sep 29, 2019 7:47 pm, edited 2 times in total.

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Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

Kev994
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Joined: Wed Aug 28, 2019 6:00 pm
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Leaf Number: 309727

Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 7:43 pm

cwerdna wrote:
Sun Sep 29, 2019 7:08 pm
You sure it's happening at 80% on the dash display? On my current and former '13 (obviously only 24 kWh), the L2 ramp down never happens until the car's in the 90ish% on the dash display... more like 94+%.
Not very sure at all, I’m eyeballing off a graph with a poor scale, and now that I think of it, the x-axis shows time, where I was thinking of it as SOC
2016 SL Coulis Red

cwerdna
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 7:46 pm

^^^
Would be curious to know... also, don't use NissanConnect/Carwings to check. I can't speak to '16 and '17 but on '13s (but NOT on '18+), the stupid % reported by the app will NOT match the dash display % SoC. Instead, it's only as granular as 1/12ths. So, if there are 9 battery bars visible --> 75% in the app. 10/12 bars visible --> 83% and so on... It will not show any values between 76 and 82% nor 84 to 91%.

'19 Bolt Premier
'13 Leaf SV w/premium package (owned)
'13 Leaf SV w/QC + LED & premium packages (lease over, car returned)

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

Todd1561
Posts: 11
Joined: Sun Sep 29, 2019 5:24 pm
Delivery Date: 30 Sep 2019

Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 7:49 pm

Thanks for all the thorough explanations! It sounds like I would have seen a ramp down if I let it run a bit longer. But ultimately, for my purposes, it doesn’t really matter since I’ll apparently be well into the 90s by the time I can detect it, which is much more charge than I’m aiming for. I guess I’m back to using the carwings API. Oh and I heard about the low resolution of the carwings SOC, but seems to have been fixed in the latest iteration. It’s now down to at least 1% increments.

There’s no such thing as an aftermarket home charge station than can monitor actual charge level and auto shut off, correct? All my research has shown no one can do this.

WetEV
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 8:12 pm

LeftieBiker wrote:
Sun Sep 29, 2019 6:36 pm
As I understand it, the 80% tapering only occurs with DCFC stations, not L-1 and L-2 stations, and the station determines when it should happen, not the onboard charger, which isn't used in DC fast charging. There is some tapering on L-1/L-2 charging, but as you found, it happens in the nineties state of charge range.

Someone correct me if I'm mistaken.
The car controls the DCFC session, not the station.
WetEV
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