I’m looking at purchasing an EV at some point in the near future and am researching potential chargers. I see that Polestar currently have an offer for a free, installed EVNex E2 home charger, and I’m curious about how it integrates with the Tesla Powerwall 3 (which I currently own)
Ideally, I would like it if the EVNex could be configured to:
Only charge via excess solar (which I believe is achieved via EVNex solar charging), i.e. monitoring grid exports
Not charge from battery under normal circumstances (i.e. the grid is up)
Be able to charge from solar (+ optionally battery) when the grid is down
The added wrinkle is that, as an Amber Electric customer, I’m continually curtailing my solar export during times of negative FIT. Would that mean the EVNex would assume that no excess solar is being produced and thus not charge the car?
Additionally, as I have a single-phase home with a maximum export limit of 5kW, does that mean the maximum that the EVNex would be able to charge the car at (from solar) would also be 5kW, despite the fact that the Powerwall 3 has a built-in 11kW inverter that my solar setup is able to hit quite often?
As I understand it, EVNex does not present a public OCPP endpoint, so services like Charge HQ which would otherwise perform the Amber <—> Tesla legwork and just tell the charger what to output at, are not compatible with EVNex
Just looking for some guidance on how might an EVNex charger work in this type of situation. A free installed charger sounds good to me, but not if I’ll need to compromise significantly on functionality.
Yes you’re right, the excess solar charging would be normal behaviour handled locally by the charger. Having said that, when the grid is down there is no “excess” going out to the grid so the charger can’t use solar charging under those circumstances.
Not charging from the battery is nuanced and depends on decisions about where it gets wired into your ecosystem. With a Powerwall 3 you can either wire it in to be invisible to the battery (in which case you could never drain the battery into the car - even when the grid is down), or to be backed up (in which case the Evnex settings can prevent draining the battery under solar charging, but not when charging at full speed - but you can charge when the grid is down).
With Amber we are about to start work on an integration which I think would enable you to use the Amber pricing to initiate charging - so you could have a rule that when the price goes negative you start charging.
For the 5kW export limit, I have seen some inverters which would correctly recognise that you are able to generate more than that as long as it is consumed locally, but some not - I suspect this is a configuration choice on the PW3. The E2 can certainly be set up to initiate solar diversion at different levels of export and try to target different levels of export so should be able to work with whatever your inverter is capable of.
In short, I think there are some relatively minor compromises (particularly if the grid goes down), but in the main an E2 would perform well for your setup. If you live somewhere with frequent outages that could be significant for you, but otherwise probably not. And of course you could use a 3-pin charger if the grid is down (as you might well want to only charge at 2kW anyway).
Evnex handles this perfectly. I have my “Target Export” set to 4KW. So
First the battery charges
Then I export 4KW of solar generation back to the grid
Any excess goes to the car
Overnight, the Powerwall just does it’s own thing. It learns when the car charges (For me, At 11pm) and will predict how much power it can give to the car while keeping enough for tomorrow. If it’s raning tomorrow, it’ll pull 100% from the grid as the car charges then goes back to feeding the house. If tomorrow is sunny, it might charge 100% from battery.
Only thing I wish was that Evnex had a 2x dispenser EVSE so I could plug both EVs in without having to switch the cable between cars in the morning. Installing a second is sadly not an option.
I have an X22 3-phase charger, 2x Powerwall 2 and peak generation of 23 kW of solar. Keep in mind that charging the car requires a minimum of 4.5 kW of excess solar to commence charging - is 1.5 kW with single phase. This is the default behaviour:
Under 10 kW of solar the PW charges first, then the car will charge when PW are full.
between 10 kW and 14.5 kW of excess solar the PW charges first at 10 kW with the rest going to the grid. The car will charge after the PW are full.
over 14.5 kW excess solar, the PW will take the first 10 kW and the car will take the rest.
If the car is plugged in, I want the car to charge before the PW so the default behaviour is frustrating. On a sunny day it’s not a problem, but on a cloudy or partly cloudy day it is frustrating. If I wanted the PW to charge first, I simply wouldn’t have plugged the car in. I have found a work around to fix the default behaviour the way I want it so the car has priority over the PW.
If the solar generation is low and I want to charge the car from the grid, the default behaviour is to drain the battery and take any excess from the grid. I don’t want to do that so I have to manually set the PW backup reserve percentage to the current PW charge level to stop the PW draining, then manually setting it back to 0% afterwards.
People have automated the process of setting the Tesla reserve level when charging their car from the grid with some clever open source Python scripting with chargers that support OCPP. Unfortunately, the last time I looked Evnex chargers do_not support OCPP so this method isn’t possible. There may be a way to automate this with Evnex chargers, but as I have only charged from the grid twice I haven’t looked into it.
One of our customers has written a python library (and Home Assistant plugin) for Evnex chargers. It’s unofficial and thus not something we test every change against (so future updates may break things), but we don’t have any intention to stop it working.
I am in NZ, I have a PW3, 10.8kWp of solar panels, Evnex E7 and a 5kW export limit. We don’t have -ve feed in tariffs over here so my use case is a bit simpler but hopefully this still helps.
I got my installer to wire in my Evnex on the non-backed up side of my gateway so my Evnex is not available during an outage. I chose this way as I didn’t want to wake up in the morning after a Power outage to find a partially charged car and an empty battery. If I want to charge the car during an outage then it will likely need to be slow so will use my granny charger. This does mean that the consumption of the charger is still visible to the PW3 though which I really like as it is my 1 stop shop to see my household power usage.
FYI I think you can get an extra CT added to the charger and then the PW3/Gateway can be told CT1 is a car charger.
As my night rate power is cheaper than my solar feed in tariff I have configured my settings to make the most use of my export limit. I make use of Time-based control on the PW3 due to my low cost for overnight power. And then I charge off excess solar during the day if the car has any space left. I have configured the Evnex app so charging doesn’t start until export is >4.5kW. Charging stops when export is less than 2kW and the Target export while charging is 3.5kW.
Attached a screendump as an example of how this seems to work on a daily basis…
At about 12pm battery was full enough, but the car wasnt plugged in so the solar started clipping as we hit our export limit. I spotted this and plugged the car in at about 1pm. The blue line (household load) then tracks the solar curve down through the afternoon, until there isn’t enough sun to keep charging the car. All while maximising the solar generation and the export limit.
@sparkY1000 Does that also mean your charging rate is capped at 5kW (i.e. your export limit), regardless of what your solar is currently able to produce?
