Stop charging when solar PV stops generating

[glynhudson]

Currently, when charging using "Eco Mode" (solar PV divert) the EVSE will continue charging at the lowest current (6A) forever until the EV is fully charged even after the solar PV has stopped generating.

A highly requested feature is for the charging to stop after the solar PV has stopped generating. This will allow users to then use a timer charge to topup the remaining amount required during off-peak hours.

I propose changing default Eco Mode behaviour to start the charge once solar PV / grid export > 500W for 15min and stop the charge if solar PV / grid export < 500W for 30min.

This feature should be backported to ESP8266.

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As an advance option the user could adjust these parameters, however minimum values should be set e.g >100W for 10min stop to avoid excess contactor wear caused by regular stopping / starting.

Another extension to EcoMode is for the charger to revert to charging at full power if the timer becomes active during an EcoMode charging session.

[jeremypoulter]

Looking through the code the divert calculations are all done on current, and we have a min of 6A defined for turning on the charge (this is part of the spec right?) so would it make sense to use this for turning off (1440w), rather than 500w?

[jeremypoulter]

Also see #62

[glynhudson]

As discussed here is some solar PV data which can be used for testing. Data is in Watts in CSV format with datetime string:

CSV solar PV data.zip

[chris1howell]

The key is to this issue is avoiding cycling the relay on/off hundreds of times during the course of the day. There will likely need to be some time and power conditions that need to be meet to justify cycling the relay in both directions.

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On Wed, Mar 18, 2020, 7:59 AM Glyn Hudson ***@***.***> wrote: As discussed here is some solar PV data which can be used for testing. Data is in Watts in CSV format with datetime string: [image: day1 - 2khWp - variable output] <https://user-images.githubusercontent.com/758844/76958434-a01e7d00-690f-11ea-8680-dbe1c64e8553.png> [image: day2 - perfect sunny day 2 1kW max] <https://user-images.githubusercontent.com/758844/76958433-9f85e680-690f-11ea-8a81-8612cf353c5d.png> [image: day3 - poor solar pv] <https://user-images.githubusercontent.com/758844/76958432-9eed5000-690f-11ea-8292-091969afd161.png> CSV solar PV data.zip <https://github.com/OpenEVSE/ESP32_WiFi_V3.x/files/4348792/CSV.solar.PV.data.zip> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#54 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN5QH5BYKLQND6R4QONTA3RICZRFANCNFSM4KSYXLRQ> .

[jeremypoulter]

For openness I am going to write a wrapper around the divert module so I can replay those CSV files and see the results.

My current thinking is that we use a rolling average to smothe out the wave so hopefully won't cause a transition too often.

Will welcome any other CSVs of different usecase.

[jeremypoulter]

I have been doing some initial work in Google Sheets:

https://docs.google.com/spreadsheets/d/1GQEAQ5QNvNuShEsUdcrNsFC12U3pQfcD_NetoIfDoko/edit?usp=sharing

This is just applying a simple smoothing algorithm. Has some fairly reasonable results. comments welcome.

[glynhudson]

As discussed here are CSV data exports for Grid Import export feeds:

Grid IE CSV rev2.zip

[Zuikkis]

Perhaps there should be a way to configure EV battery size, so OpenEVSE would know how critical it is to use solar power fully?

I have 10kWp plant and I'm charging an Outlander PHEV which takes about 9kWh from empty to full, so it's not really all that important for charge curve to follow solar output perfectly. But I don't want to use any bought electricity at day time..

So for me, it would be ok to have like 1-2kW safety gap to avoid going over the solar output.

[jeremypoulter]

@glynhudson the Grid IE CSVs only had the solar in, not the Grid IE

[jeremypoulter]

@Zuikkis The biggest problem is not necessarily knowing how much charge the car needs (although this may help) but knowing how much power you are going to get from the solar. You only know what has happened and (short of getting in to full on AI/ML) it really hard to predict what is going to happen. So putting too large buffer in there is could very well result in no charging.

[glynhudson]

@glynhudson the Grid IE CSVs only had the solar in, not the Grid IE

It's been fixed now, please download the rev2 CSV attached to the post above.

[jeremypoulter]

@Zuikkis Would you be able to share a few exports of your solar system? May be good to have some examples of such a large system.