Ev charging: "smart load" outputs vs main panel

[SolarElectrocution]

Hi!

I am in Northern California (SF Bay Area) and in the process of building a new house. I have a 400amp main panel (grid-tied) in PGE territory, and will be looking at ~10KW of solar with 2 EG4 PowerPro batteries storage (pretty much required with NEM 3.0). The house is all electric and I have 2 EVs fed off a single 100 amp breaker. I am considering an EG4 18kpv, the GridBoss and a Sol-Ark 15k for the connection from grid <-> critical loads.

With NEM 3.0, I want to maximize the amount of "self-consumption" and reduce the power draw from the grid (which means pulling from the stored energy where possible). On the other hand, if the grid goes down I do not want to use the solar batteries to charge the EVs.

Given this I am trying to understand if I should just install the EV breaker in the main panel, or if there there any benefits from connecting the EV load to the "smart load" connection of these hybrid inverters? If am not missing anything, the major benefit I might get is that I could optionally turn on the EVs in the case when the grid is down, but I still have excess PV production; is that accurate?

Power goes down very rarely (I've only had only 2 or 3 power outages in the past 10 years or so, and nothing that lasted more than a few hours). In the normal course of events I will be plugging in the EV at night and begin charing at 12pm or so, when off-peak power is at its cheapest. I would expect the batteries to help out until their SOC drops to some threshold, and then the rest of the power would come from the grid.

 

[billvon]

Given this I am trying to understand if I should just install the EV breaker in the main panel, or if there there any benefits from connecting the EV load to the "smart load" connection of these hybrid inverters? If am not missing anything, the major benefit I might get is that I could optionally turn on the EVs in the case when the grid is down, but I still have excess PV production; is that accurate?

Yes.

If your grid rarely goes down I wouldn't bother. Use the (high current) charger in the main panel for normal charging. If power goes out, use a level 1 charger plugged in to a backed up outlet.

If you really want to get fancy put a 240V 20A outlet somewhere on your backed up loads; that will let you charge at 3800 watts (and charge more efficiently.)

 

[BentleyJ]

If you are going to install the GridBoss, one of the smart ports is good for up to a 125A breaker so you wouldn't be giving up anything by installing the EV breaker in the grid boss and then if you do get a rare outage the Smart Port will automatically shut off per your settings and not drain the solar batteries.
Speaking of batteries if you do connect the EV charger to a smart port, so its on the back up system, I would recommend adding more solar battery capacity. Two batteries are not going to give you much run time with a large house AND and EV.

 

[SolarElectrocution]

> Two batteries are not going to give you much run time with a large house AND and EV.

Agreed. Taking this one step further, this means that I would not ever even want to charge the EV if the grid goes down, and therefore there is not much reason for using the smart ports at all for this purpose. This way, I can get by with fewer batteries too, saving some cash.

 

[peufeu]

With 10kW PV you would benefit from using an EVSE instead of just plugging in the EVs in normal sockets. If you get an EVSE that allows it, charging current can be adjusted on the fly to follow PV production. It also allows much higher power than a socket.

However it is complicated to configure, due to the first rule of PV: nothing is compatible...

Here's a charging session on mine.

 

[SolarElectrocution]

With 10kW PV you would benefit from using an EVSE instead of just plugging in the EVs in normal sockets. If you get an EVSE that allows it, charging current can be adjusted on the fly to follow PV production. It also allows much higher power than a socket.

However it is complicated to configure, due to the first rule of PV: nothing is compatible...

Here's a charging session on mine.

View attachment 296589

Nice! Which EVSE are you using? I currently have two Teslas on a Tesla wall charger, but I have favorable net metering due to NEM 2.0 and so just charge at full power during off peak times at the house we are living at while the new place gets built. Things change with NEM 3.0 and batteries, and I would very much like to do what you described once the house gets rebuilt.

A bummer for me is that I don't work from home during the weekdays, so I can't really soak up excess summer production optimally

 

[peufeu]

I have ABB Terra, but I don't recommend it, the EVSE is nice but the app is garbage.

With a battery hybrid inverter, the main issue is compatibility. Some EVSEs do support PV by measuring exported power and using it, but if you run zero export, there's no export to measure, so... bummer it doesn't work at all!

And they have no idea what the PV battery is doing. So they can't :

- Give priority to charging the PV battery up to a certain SOC, say 80%, then give priority to charging the car.
- Discharge the PV battery into the car at night up to a certain SOC, but not more

This leads to the more general problem of power routing: it would be nice to be able to direct excess PV to various uses like EV charging, heating, AC, hot water, etc. To do that you need a brain box that talks to the inverter to get battery SOC, charging current, export power, etc.

But... first rule of PV: nothing is compatible! So there isn't any good readymade solution that will work with most inverters and EVSE's.

You could use evcc which seems nice but it's single minded: it only charges EV.

I ended up with python running on a Pi. The reason I chose this EVSE is the charging current limit can be set locally via modbus, so my python scripts tweak it, no cloud bullshit, no smart charging subscriptions, etc.

Do you code?