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Discussion Starter · #1 · (Edited)
Owners of Leaf's made after 2015 will know there is no way to charge to less than 100% other than keeping an eye on the charge level and physically unplugging it, or if you have a smart charge point commanding the charge point to stop charging via its app. For those who want to charge to less than 100%, especially over night when you're asleep this is quite frustrating to say the least. I simply don't need 100% charge to do my 37 mile commute and would rather only charge to 80% most days, and certainly on the weekend I don't want to charge to 100% then find I might not even go out or only go to the shops.

I've been wracking my brain for weeks trying to figure out a simple, automated way to do this without complicated custom scripting running on a server that polls the car for SoC via the Nissan API then commands a smart charge point to turn off at the right time. It's certainly possible to do it that way in theory and I have the python coding ability to pull it off, but there are many pitfalls to that approach that I've considered and it's quite complicated to do the logic right and have it not get in the way of atypical use patterns. It would also fail to work if the Nissan API went down. Instead, I think I've come up with a fairly simple, elegant solution that almost anyone can implement that is "good enough".

Before going any further the intention of this thread is to be about how to automatically charge to 80%, not why you should or might want to do so. There are plenty of other threads to debate whether there is any benefit to charging to 80% vs 100% and this is not that thread...

One kludge that sort of works in a limited set of circumstances is to abuse the charge timer by setting the charge end timer about 2 hours 20 minutes (for a 6kW charger car like mine) after the desired departure time. With no start time set the car will automatically calculate the start time based on how depleted the battery is, aiming to be finished charging 2:20 after you will actually be leaving - by which time it will be around 80% charged plus or minus a few percent.

However there are many problems with this kludge:

1) It's quite sensitive to departure time especially with a 6kW charger. If you're even half an hour later than usual leaving you'd likely be at about 95%, and if you were half an hour early you could be as low as 65%. If you don't leave bang on the same time each morning this solution is not really workable.

2) Some Leaf's, including mine have a "bug" where the climate control timer overrides the charge timer. For example if I set the charge end timer to 10am (2 hours 20 minutes after my 7:40am departure time) and the climate departure timer to 7:30am, the car will fully charge exactly 2 hours before that - eg 5:30am, completely neutering this kludge. So on my car at least, the late charge end timer kludge only works if I disable the climate timer.

3) This kludge brings your charging time forward to morning peak usage times while you're getting ready for work - such as electric shower use etc, and puts it outside the cheap 12:30 to 4:30 period of many dual rate tariffs - so it is not compatible with using a dual rate tariff. (Which I'm thinking of switching to)

4) If you do need 100% charge the following day (say a long Saturday outing) you would either have to override the charge timer when you plugged the car in or before bed, or edit the charge timer in the car to be earlier - neither particularly convenient.

My proposed solution - not yet tested, is to combine the charge timer in the car with the schedule/manual overrides of a smart charge point. I don't actually have a smart charge point - just a dumb Rolec, however I plan to fit a Shelly 1 in the Rolec (controlling the low voltage pilot control line) as others here have done to essentially give the Rolec the ability to schedule charging with app based override.

My week day departure time is 7:40am, and I want timed climate control set to 7:30am departure.

I would set the charge end timer in the car to 5:30am and the climate timer to 7:30am. I would then set the schedule for the Shelly/Smart charge point so that it is on all the time except 3:10am to 5:40am, when it is off.

Here's how this would work:

1) I get home in the evening and plug the car in immediately as I do now. The charge point is on, but the charge timer in the car defers charging. The car calculates when it should start charging based on battery SoC and charging speed available. Lets say the SoC is 50% and it has decided that will take 3 hours including balancing to reach 100%. Because the end timer is set to 5:30 this means it will start charging at 2:30am.

2) The car will charge from 2:30am until 3:10am when the Smart charge point schedule will stop the car charging. Hopefully at this point the car is at about 80%, or whatever the desired charge level is. The charge level can be tweaked by adjusting the 3:10am turn off time of the smart charge point - setting it earlier will result in a lower SoC, later a higher SoC. The charge end timer in the car is left alone at 5:30am.

3) At 5:40am the charge point will turn back on again however as this is after the 5:30am charge end timer of the car the car will not resume charging and remain at the same SoC attained at 3:10am, eg approx 80%.

4) About 30 minutes before the 7:30am climate departure time (more in very cold weather) the climate control in the car will come on and be able to work as normal as the charge point is back on again by this time. The climate control will come on without charging the car to 100% - in practice the SoC does creep up by about 2% each time the climate control starts when the SoC is below 98% but this is not a big deal.

Using this combination of timers it should be possible to plug the car in at night and have charging deferred to early morning cheap rate hours of dual rate tariffs, reach a target SoC fairly consistently (no variations due to departure time or initial SoC) and have timed climate control without the usual interaction between the two timers.

If you want 100% charge on particular days, no problem - there are two possible approaches, both easy to implement.

1) If you know ahead of time you want 100% charge tomorrow or on a certain day of the week, simply disable the 3:10am to 5:40am "off" schedule on the smart charge point for that day using the app for the charge point, this will allow the car to continue charging all the way to 100% as it normally would.

2) If you don't know ahead of time but decide after getting up that morning that you are going to make a long trip that needs 100% (spontaneous weekend trip for example) simply use the Nissan app remote charge start function, or press the charge override button inside the car. By this time of the day the charge point schedule will be on again so overriding the cars charge timer will allow it to finish charging from 80-100% which on a 6kW model only takes about an hour or less, so would be near enough to 100% by the time you were ready to depart.

I've ordered a Shelly 1 to install in my Rolec so I'll let people know whether this combined timer approach works well in practice, but I don't see why it wouldn't... :)
 

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GOLF GTE PHEV
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Seems a rather complex way to limit charging. If you know the charging rate at home, you can surely just adjust the car timer?
Alternatively, don't plug in the charger every night.

For example my E+ charges at 6.6kw and in the 4hour Octopus Go window, will add about 45%, (25kwh) so to avoid reaching 100%, I only connect the charger when the SOC is below about 50%. I never need to alter the timer.

On the Leaf 2, I honestly believe the BMS is capable of managing the charging such that no harm is done charging to 100% daily at home, which is precisely why the 80% charge option has been removed.

The current starts to drop from 95% and after 98% is a mere trickle anyway - i.e. completely harmless to battery longevity.

Also, you seem to fear having a100% charge and then not driving the car for a day or so, why?
This is only an issue if you left the car for weeks.
 

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Discussion Starter · #3 ·
Thanks, but you missed the part of my post where I said I don't want to discuss the WHY in this thread, only the HOW.... ;)

Any time charging to 80% is mentioned on this forum it results in a long debate with a lot of opinions expressed by a lot of people, the majority of whom don't really have any understanding of how and why battery degradation occurs, and I don't want this thread to go down that rabbit hole. There are plenty of other threads for that.
 

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What you are suggesting should work, but why not just set both a start and an end time in the car? If you're doing 37 miles most days you'll probably need to charge for about an hour and a half to get back to the charge you started with so just set the timers to give you that - either 06:00 to 07:30 based on your departure time or 03:00 to 04:30 if you change tariff. You will sometimes need to adjust the timers but that seems less effort than what you're planning.
 

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The shelly 1 is a great addition to a dumb charge-point.

Yeah, quite an interesting problem to solve. Lot's of moving parts in this puzzle. Cheap rate electricity times, starting battery percentage, and heater draw.

I guess you could even have various routines setup on say Alexa for different seasons of the year. I dunno, just musing.

Cheers
 

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Discussion Starter · #8 · (Edited)
What you are suggesting should work, but why not just set both a start and an end time in the car? If you're doing 37 miles most days you'll probably need to charge for about an hour and a half to get back to the charge you started with so just set the timers to give you that - either 06:00 to 07:30 based on your departure time or 03:00 to 04:30 if you change tariff. You will sometimes need to adjust the timers but that seems less effort than what you're planning.
Well, fiddling around with the charge timers in the car all the time is exactly what I'm hoping to avoid. If I set a start time in the car it disables the automatic charge time calculation which takes into account the current SoC before charging.

With a fixed start and stop time even if I used exactly the same kWh per day the SoC would drift up or down over just a few days due to charging not perfectly matching use, requiring me to keep making manual corrections. And while I average 37 miles a day the energy consumed to do that varies greatly from day to day, sometimes I have to take alternative routes due to traffic, sometimes we do extra errands, weather differs, and weekends of course are completely different, sometimes no or almost no driving, sometimes >100 miles.

A key part of the technique I'm proposing is making use of the charge end timer mode where the car calculates the starting time for you - by using this the SoC achieved at the end of each charging period should be pretty consistent maybe +/-5% (yet to be determined) and not be affected by changes in mileage or miles/kWh, and not drift out over time, eg zero maintenance.

So while it might take slightly more setup (two timers to program instead of one, and I'm having to actually add a timer to my charge point as it is currently dumb and doesn't have one) once set up it is literally set and forget - just plug the car in each night and trust it to do the right thing, which is charging (mostly) during cheap hours, charging to the desired SoC and still allowing plugged in preheating to work.

For those occasions where I might need the full range (usually only on a weekend) I have an easy app based override available which means provided the car was plugged in I don't even need to leave the house as I can use either the charge point app or Nissan app to extend the charge to 100% when needed.

It also deals a lot better with weekends than what I have now. Currently I have a charge end timer of 7am Monday-Friday and on the weekends no timer, so it simply doesn't charge automatically on the weekend. So if I plug in on Friday night the car won't charge until Monday morning unless I override it with the Nissan app or press the button in the car.

As I typically get home with somewhere between 45-65% (from a 100% charge) that is usually enough to cover weekend errands unless we're making a long trip. And it sometimes happens that we only do a few miles over the entire weekend or nothing at all, so I don't want it sitting at 100% all weekend so we can do 5 miles. But if we do decide to do a long trip at short notice it takes too long to charge from 50% to 100%.

So what I end up doing if I think we might be needing more than local errands on the weekend is putting the car on charge immediately on Friday night and setting a timer on my phone to remind me to unplug it after an hour or so when it should be around 80% - then unplugging it and plugging it back in to let the charge timer to block the charge, allowing me to complete a charge to 100% remotely if I need it on the weekend.

But this is a hassle, and would defeat any night time cheaper charging rate as I'd be charging early in the evening. I'm not currently on a dual rate tariff but I'm considering switching to one, so I would want to avoid charging in the early evening, and that possible switch to a dual rate tariff is what has got me thinking again about ways to automate charging to 80% in the middle of the night.

I really don't think a one off configuration of a charge timer schedule in both the car and the charge point is that much hassle - anyone who already has an app to schedule a smart charger could do what I'm suggesting with just a few minutes work and if it is zero maintenance it is low hassle in the long run.
 

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Discussion Starter · #9 · (Edited)
The shelly 1 is a great addition to a dumb charge-point.
How have you found the Shelly 1 - I've read through the spec sheets, downloaded the app and it seems to be quite amazing bang for the buck, I was going to ask in your other thread where you talked about using it but thought nah, I'll just order it. :) I have other uses for it even if it didn't work out for the charge point, and I will probably end up ordering a couple more if they work well.

How is the WiFi range? And does it keep running the programmed schedule even if it lost the WiFi connection or the household internet connection went down for a while? It would primarily be following a fixed weekly schedule with the occasional manual override.
 

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How have you found the Shelly 1 - I've read through the spec sheets, downloaded the app and it seems to be quite amazing bang for the buck, I was going to ask in your other thread where you talked about using it but thought nah, I'll just order it. :) I have other uses for it even if it didn't work out for the charge point, and I will probably end up ordering a couple more if they work well.

How is the WiFi range? And does it keep running the programmed schedule even if it lost the WiFi connection or the household internet connection went down for a while? It would primarily be following a fixed weekly schedule with the occasional manual override.
Yeah, when on Agile I had a shelly 1 in the Chargemaster and the PM model for the hotwater tank driven by IFTTT. With the demise of Agile they and more shelly's [e.g. dimmer version] are now just on light switches with voice control. So I use a combination of Alexa, the Shelly cloud, and direct communication between Shelly's say to trigger each other.

Hard to comment on the range as the wifi router is in the middle of the house so each Shelly can't be more than a few meters away in distance. There is one in the garage for outside lighting but there is a wifi access point in there as I doubt it could reach the house router.

I've found them absolutely bombproof, fit and forget, but I don't have any timed schedules atm only some triggering each other which does not require internet, you can send them local HTTP requests.

Cheers
 

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I only want to charge to 80% most of the time.

I know how long it takes to charge but the pod point schedule turns on when required but not off. It's flaky to say the least.

I have started putting it on so it gets to around 80% when I wake up. I can just unplug it then when I get up
 

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Personally, I've found using the Ohme to read the Leaf's charge levels to be unreliable. So I just set the Ohme not to login to Nissan, basically just using it as a dumb EVSE with a timer. With hindsight, I could just use the dumb Chargemaster and the Leaf's onboard timer but the Chargemaster is... well, crap for many reasons, lol.

Anyway, I'm not sure if others have found this... It appears you can't have multiple devices/services logged into your Nissan Account at once which perhaps could be the issue? Say, the car, Ohme, App, Google Maps etc.

At the end of the day Ohme costs £199 vs Shelly 1 @ £12.26 from Amazon and the Shelly's capabilities are only limited by your imagination.

Cheers!
 

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Discussion Starter · #14 · (Edited)
Why not just buy the Ohme cable for £199 that way you can just set it to stop giving your car power once it hits 80%?
And how prey tell would the Ohme know when the car was at 80%? The J1772 protocol provides no way for a charge point to detect the state of charge of the car.

The only way it could be detected is by periodically polling the Nissan API but this has multiple issues.

1) Doesn't work when the API is down - happens from time to time, and enough that I wouldn't want to rely on it.
2) Logs out the smart phone app so you need to keep logging in again. Very annoying.
3) Wakes the ECU's in the car every time you poll, so risk of running the 12v battery down if you poll excessively when the car is not topping up the 12v battery. So you'd need heuristics to figure out when it was OK to poll the car frequently and when you had to back off to avoid discharging the 12v battery.

I've considered a lot of these issues already when I was considering polling the Nissan API myself to control the Shelly switch. It can certainly be done, but sometimes simpler is better and more reliable.
 

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And how prey tell would the Ohme know when the car was at 80%? The J1772 protocol provides no way for a charge point to detect the state of charge of the car.

The only way it could be detected is by periodically polling the Nissan API but this has multiple issues.

1) Doesn't work when the API is down - happens from time to time.
2) Logs out the smart phone app so you need to keep logging in again.
3) Wakes the ECU's in the car every time you poll, so risk of running the 12v battery down if you poll excessively when the car is not topping up the 12v battery.
So how do the E.Volt rapids display the SOC of my Leaf?
There is clearly a protocol for data to be sent to the charger that includes SOC.

P1901 powerline communication update to the standard and

In 2011, the HomePlug Green PHY specification was adopted by Ford, General Motors, Audi, BMW, Daimler, Porsche, and Volkswagen, as a connectivity standard for Plug-In Electrical Vehicle.[5]
 

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Discussion Starter · #16 ·
So how do the E.Volt rapids display the SOC of my Leaf?
There is clearly a protocol for data to be sent to the charger that includes SOC.

P1901 powerline communication update to the standard and

In 2011, the HomePlug Green PHY specification was adopted by Ford, General Motors, Audi, BMW, Daimler, Porsche, and Volkswagen, as a connectivity standard for Plug-In Electrical Vehicle.[5]
DC Rapid charging uses completely different communications protocols to AC charging. AC charging (both Type 1 and Type 2) uses J1772 signalling which is not even digital communication, just a bit of simple logic and some pulse width modulation of a square wave:


There is nothing in J1772 signalling which allows a charge point to know the SoC of the car.

Rapid charging uses actual digital communication - Chademo uses CanBus and CCS uses Green PHY. Both of these allow the car to communicate their state of charge to the charger.
 

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I only want to charge to 80% most of the time.

I know how long it takes to charge but the pod point schedule turns on when required but not off. It's flaky to say the least.

I have started putting it on so it gets to around 80% when I wake up. I can just unplug it then when I get up
I don't have a home PodPoint to check but I am on their mailing list which a couple of weeks ago announced an upgrade to their app that sounded as though scheduling was being improved.
 

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DC Rapid charging uses completely different communications protocols to AC charging. AC charging (both Type 1 and Type 2) uses J1772 signalling which is not even digital communication, just a bit of simple logic and some pulse width modulation of a square wave:


There is nothing in J1772 signalling which allows a charge point to know the SoC of the car.

Rapid charging uses actual digital communication - Chademo uses CanBus and CCS uses Green PHY. Both of these allow the car to communicate their state of charge to the charger.
Thanks for that clarification.
It's not technically impossible to use a version of PWM called single edge nibble transmission - SENT to send the charge status but the frequency is normally much higher than 1Khz.
 

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Thanks for that clarification.
It's not technically impossible to use a version of PWM called single edge nibble transmission - SENT to send the charge status but the frequency is normally much higher than 1Khz.
It might be NOT TECHNICALLY IMPOSSIBLE, but if it's not implemented by the vehicle you might as well be trying to charge somewhere on the dark side of the moon for it's going to help.
 

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Discussion Starter · #20 · (Edited)
It might be NOT TECHNICALLY IMPOSSIBLE, but if it's not implemented by the vehicle you might as well be trying to charge somewhere on the dark side of the moon for it's going to help.
CCS of course sends 10Mbit Green PHY IP data over the same low voltage pins that AC charging uses for the old fashioned 1Khz pulse wave modulation, (since the CCS connector only adds two more high current DC pins there wasn't any other choice but to repurpose existing pins for data) so CCS cars know how to send digital data over these lines, however this was originally only added for use in CCS DC rapid charging mode not for AC charging, eg the cars still use the traditional 1Khz pulse waveform method when AC charging.

I vaguely remember reading there was a push to add this smarter Green PHY communication for AC charging on CCS cars, however I don't know if that was ever ratified or if it was whether any cars have implemented it yet, let alone AC charge points.

For cars that are Chademo, including all Leaf's, it would not be feasible to implement this as Chademo uses CanBus so there is no implementation of the Green PHY protocol in the car that could be hooked up to the AC socket. So I think its extremely unlikely that we will ever see "smart" communications for AC charging on cars that use Chademo, at least outside the Japan domestic market where they will probably come up with their own incompatible system.

For CCS cars I think it's something we'll see eventually but it may take a long time for all new cars and charge points to support it. One advantage of the old J1772 system is that it's incredibly simple and reliable - it can be implemented in a small amount of discrete logic without even an integrated circuit let alone a CPU if you want, and works very reliably with excellent interoperation between different brands of car/charge point.

CCS's Green PHY protocol is notorious for being over complicated and poorly documented such that different manufacturers interpret the spec in incompatible ways. Even now incompatibilities between CCS cars and rapid chargers are being ironed out with firmware updates on both sides. So adding Green PHY to the typical home charge point would add considerable cost and complexity in implementation for little gain and actually make it less reliable and compatible!

Most of the advantages of smarter communication between the car and charger (such as identifying the car for billing purposes) would be for public charging not charging at home.
 
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