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markess asked

EV Charging Station - ESS system location

In the EV Charging Station Manual is shows it can be installed either on the AC input or AC output of the inverter charger.

I have a domestic on-grid ESS system with my house and most PV on the output of the Quattro (and some on an MPPT direct to Pylontech).

What is the difference in functionality between putting the EV charger on the input or output of the Quattro?

I assume if it's on the Quattro output then when charging the car from the grid the whole house (also on the output in my case) must also be on-grid too. If it's connected grid-side on the inverter input then presumably you can EV charge from grid whilst the house remains on the home battery?

There is not much text in the manual describing this difference in location.

I wonder how the ESS grid set-point parameter affects behaviour in each case, for example.

I assume if I place the EV charger on the Quattro output and limit the pylontech battery to 0A/idle (using Node-RED for example), then the power that would have been exported to grid will go to the car instead?

Thanks

ev charging station
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matt1309 answered ·

Hi @MarkEss

There's a few things to flag. I think the main thing you're missing is that if you integrate the EVCS into GX/venus os system then it's treated as a normal load, therefore there's no difference between pros/cons of EVCS on ACIN vs ACOUT and the pros/cons of any power load being on ACin or ACOut. It's not treated as a separate thing just a normal load.


Therefore in ESS if the EVCS is integrated it's just seen as an AC load so whichever side you put it on the battery will cover EVCS unless you configure it otherwise (node red) and assuming grid is not down. (That is assuming you have grid meter on ACIN If you don't have an grid meter on ACIN then you may have issues)


The behaviour you're describing/expecting by having EV charger on ACIN is more like what you'd get if you used a system that doesn't communicate with Victron like a Zapi ev charger where you use Ct clamps to monitor/capture excess power being exported which is then used to determine how much to charge the car.


The Victron EV charger has communication with gx device so no need for CT.


The main differences in my view of putting on ACIN vs ACOUT are therefore exactly the same as putting any other load on either side:

EVCS on AC Out:

1. Will stay on during grid outages

2. EVCS charging rate may be limited depending on size of quattro. ie if grid is on but max passthrough of the grid through quattro isn't enough then you may have limited charging speeds on EVCS (unlikely for quattro given they tend to be bigger but if you have a small multiplus this may be a consideration).

ie large AC loads 4000w, Car charger 7000w, quattro needs to be able to supply 11,000w, if Quattro cant passthrough enough grid then EV might be limited.


EVCS on AC In:

1. Not limited by quattro/multiplus max passthrough.

2. Will not work when grid goes down.


I imagine the location of EVCS (ACin or out) is also required/used by victron system to calculate the car charging current in automatic mode correctly.


In terms of setpoint, as it's treated as a normal load it's factored in on AC IN or OUT.

You're 100% correct if you use a zappi ev charge though, that monitors exported power. ie if you make setpoint -1000w the zappi should charge by 1000w by monitoring amount exported to grid via ct.


Again with your last statement, that's true for a zappi ev charger. With a victron charger you'd need to write something like that in node red. At the moment the auto mode uses excess power that would be exported when battery is at 100%/absorption phase, essentially just putting into car rather than exporting. If you want to stop battery at x percentage and put any extra into car you'll need node red. (I'm hoping those types of features get added in firmware updates as using node red is never as clean as a supported feature)


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markess avatar image
markess answered ·

Thanks @matt1309

My Quattro has 100A passthrough capability, so with 7kW EV charger that leaves me 17kW for house (so no issues) Also I don't have a grid-side meter (since all loads are on ACout).

So looks like putting EV charger on the inverter output should be OK.

I now understand EV charger is just considered as a normal load for ESS GX calculations. I can use Node-RED to read home battery SOC and then adjust grid set-point dynamically (say every minute) to make home battery current 0A. The PV export should then go instead to the car (if empty).

I currently do similar to export all PV 4-7pm due to export tarrif.

I hope I understood it, thanks for the explanation.


This should work unless the EV charger actually looks for 100% SOC rather than exported power. I assume it uses exported power rather than monitoring the battery SOC, so if I generate an export it will be picked up regardless of battery SOC

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matt1309 avatar image matt1309 commented ·

No worries, @MarkEss

There's an auto mode that will do what you want but only at 100%/absorption phase. You can trick auto mode into working outside of 100% but I'm not sure if adjusting setpoint is what you're after though, as that will just export the excess rather than putting it into the car. The car auto mode does absorb excess in auto mode but by adjusting setpoint you'd just end up exporting it instead.


You could use auto mode and try setting max charge current in DVCC to 0 or close to 0 and then the ev charger should grab the rest but i've heard rumours that this only works on AC coupled PV.


I think your best bet is doing something similar to what you do to export PV but instead of adjusting set point you instead adjust EV charge current (via node red).


So EV charge current = (PV produced - house loads)/240 or whatever voltage you have.

Might be tough getting house loads if you dont have a meter but maybe you could work it out ie
AC loads - current EV Charge current = house loads

new EV charge current = PV produced - (AC loads - current charge current)

and if that's negative turn off charging.


I'm hoping all these features will be added soon. I've seen a fair few people ask for them and tbh I've seen victron staff reply saying they've been added to the todo list so fingers crossed.



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markess avatar image
markess answered ·

Ah, ok..... maybe dynamically adjust EV charging current to keep home battery current at 0A, if EV charger is in Node-RED.



(and yes using DVCC I've seen only AC PV affected. MPPT still charges battery)


First I need to decide if this charger is the way to go or not

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matt1309 avatar image matt1309 commented ·

Yeh you've got it.

I personally just use the auto mode at the moment. However I'm hoping they add a feature where you can enable auto mode down to SoC % and similarly for schedule charging.

I'm tempted to make my own mode in node red which would work like you describe but I'd need a way of activating the mode easily which would likely involve another system (maybe homeassistant/openhab).

I've got the no screen version. It's a nice charger, with lots of potential. However does feel like a fair few features that you'd expect to exist dont exist just yet and node red is needed. Even standard things for evs like a CT on incoming supply to ensure you don't blow the fuse. I've added that into node red.


I suppose I expect to have all these features because I've been spoilt with other victron kit being so flexible having near ever configuration i can think of possible out of the box.

Saying that it is a newish product and you can do most things just requires node red. You'll see a lot of folk requesting similar features and tbf the victron staff do reply to note they've been added to their todo lists.


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markess avatar image markess matt1309 commented ·
I use the Node-RED dashboard and add a slider to enable/disable behaviour
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matt1309 avatar image matt1309 markess commented ·
I might have to look into this. I've got to make something that's approved/usable by elderly relatives... always a challenge.
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