question

@IceKream given your setup, completely off-grid I imagine that the variations in provided power from the PV should be compensated from the battery, I don't think that a continous loop which dynamically adjusts the current requested by the car is possible to be in real-time sync with the PV power. Not sure even if this is OK for the car battery to have fluctuations in the charging process.

My system is grid connected and I use the above mentioned script (https://community.victronenergy.com/questions/113114/software-attenuation-for-home-excess-pv-charging-o.html) to increase setpoint in order to draw needed power from the grid and not batteries when excess PV is not there to fill the car requirements. After some tests using the python script I see that reading from registers is a 1-second step process, I could not get faster than this. So basically I am always one second late with all measurements. This is why I used a running average of the measurements, as to avoid getting in oscillating states.

Looking forward to your progress and if I can be of any help please let me know.

@Bogdan Nedelcu, thanks for the first answer! I had a look at your script, and indeed you can adjust the power drawn from grid (your slave id 2700) whilst I can't - and yes if we minimize the power drawn from home batteries it's close to what I need. Building a similar script logic was one option I had considered (i.e. adjust car charging # amps based on most recent PV production read minus house consumption, temporarily drawing a minimum amount from house battery in for gaps in between measurements - just unsure of whether I should prefer a python modbus, ocpp or homeassistant plugins implementations).

Interestingly, if I understood your script correctly, it is mimicking what the solar kits of EV chargers do (They are an option of smart car chargers for many brands, whilst it's in Spanish, check the following video as of Min 6:10 (the icons should be self explanatory on the power generated/drawn), and if I understood your script correctly, the native solar kit app pretty well does the same https://www.youtube.com/watch?v=oJZNNQE6HZk&ab_channel=Teslavlogs

On the feasibility. If (and only if) you have a smart EV charger whose charge can be adjusted in theory it's possible. The native app allows you to set the EV charger outgoing amps from 6A (i.e. 1,380W @ 230v) to whatever power possible (in the case of the EV charger I'm looking at 32A = 7,360W @ 230v). Whilst setting it on the EV charger I'm considering is undocumented (except they state OCPP 1.6 compatibility), as the EV charger on my mind is a smart charger supporting RS 485, I could add a phoenix contact EV controller (250 euros more ...) which has clean documented ModBus. (but again ... if your EV charger supports RS 485 and if is a smart charger meaning you can adjust load in amps - which entry level EV charger never do)

Currently I've asked various people (this community, HomeAssistant communities, and various EV charging resellers) - and I'm collecting the answers. Pretty well though it's likely to be that no one knows - and that I'll have to purchase a smart charger and try out for myself.

I'll keep this thread live as I make progress and also publish all scripts I build.

IceKream

So funny thing. A friend of mine who is completely off the grid, asked me to write an app that does exactly what you describe. He wanted a way to adjust the maximum amps set on the charger, in a way that would not impact his batteries.

He wanted that any excess electricity (after subtracting household usage and batteries being charged in the morning) produced by the solar array to be sent to the EV. I ended up writing this:

https://github.com/gabriel-samfira/solar-ev-charger

This app was tested on a Color Control GX, connected to a Victron Energy inverter with a go-eCharger. The app runs on the ccgx itself, and listens to events from dbus and mqtt (the go-eCharger sends status updates via mqtt), then at a configurable time interval, if needed, sends an update to the charger, adjusting the amps to match the current solar panel excess.

It has 2 configurable thresholds to turn the charger on or off. If the available power dips bellow a configured value, it will turn off the charger, and another setting that allows you to set a threshold for when to turn the charger back on.

For example, if you dip bellow 3 amps, it will turn it off, and if you pass 6 amps, it turns it back on. This way you won't flap your charger, causing your EV to go into error state. As soon as solar irradiation goes down, the app will turn off the charger for the night.

As mentioned, this was only tested on his specific setup, but works quite well, with a decent memory footprint. With some modifications, it will probably work with other chargers as well. The license is Apache 2.0, so feel free to grab it, modify it, do whatever you want :).

Hope it helps. Cheers!

I use a "OpenWB" for that. It is communicating with victron quite well and most ob the time it uses only solar power to charge (or otherwise is told to charge from battery). Works quite well !

Maybe an option for you ?

Jens

Wallbox with modbus: Schneider Electric EVLINK

Also have a look at openEVSE Project. Works with MQTT.

Where are you located in Spain? I'm in Alicante area and have PV and EV.

Best solution is... a simple solution. You could use OpenEvse charger (https://community.victronenergy.com/questions/98827/controlling-an-openevse-electric-vehicle-charger-u.html) which is typically controlled by MQTT with energy send to grid data. But this is only a MQTT topics - you could create any data you need by NodeRed/any_data_IOT_tool to control yours charger.

Of course algorithm needs to be analysed - what is obvious: if you have fully charged battery, frequency shifting mechanism start limiting power from PV - and you could not calculate how much power is excessed (ok,you could increase charging PV until frequescy is below 50Hz, but is complicated) I think so you shpuld split the power between charging battery and the car untill battery reach 90% SOC - and than charge car with full PV power. That algorithm have to be tuned for yours needs.

This is not true that you unable to charge from battery storage - PV charger is normal load as any other - that guy normally charging his car that way in off-grid garrage (https://www.youtube.com/watch?v=PbzTmk5mzr8&ab_channel=Off-GridGarage)

I got the solution to work with Node Red to my liking. I'll add more details on this in an upcoming youtube channel I am planning to build. I continuously improve the system.

hey @IceKream,

I have some recommendation for you. As you question 3c) ... "Can someone recommend any programmable car charger that has natively proper ModBus register documentation"

So there is one cheap car charger with rs485 and Modbus (connector and MODBUS firmware is available, but remember to note it during ordering process!!) That simple and cheap device is not contain any ModbusTCP, or OCPP (so no internet to the device) !!!
http://evracing.cz/evse-din-RS485-residual-current-monitor-6ma-DC-30ma-AC

http://evracing.cz/simple-evse-wallbox

well documented manual with all signal explained:

http://evracing.cz/evse/evse-wallbox/evse-wb-din_latest.pdf

firmware updates available here:

http://evracing.cz/evse/

Until now I was not able to finish the communication, as time squeeze (three children)...

Altrough I use that one at home (sucessfully for five years), I decided now to buy a better device with Bender CC613 (with webserver, ocpp, ...), becouse I could now charge two cars (one stupid, one smart).

Now I fight with Victron 48V, Node-Red and OCPP. :-) So any hint appreciated. Currently I am able to read data from my Offgrid Victron, compute the dynamically SETTING the available # amps for EVs. Now I beginning my work on the data communication in between Node-red and OCPP chargers.

Have you somebody any experiences how precisely (which current smallest step) is possible to drive the car chargers using OCPP. My old EVSE cherger curent step was relatively rough: 6A, 10A, 16A... But my smart-car can regulate the energy consumpion much softly. That is much appreciated function, especially for off-grid systems.

I still do not know for sure as if the charger itself is an important part of the off-grid charging game, or as if it is the more the direct communication with a car itself. I know the available grid current have to be limited strictly by charger, but the off-grid (excess sun) available energy is another level game.