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Charge Current Limiting Based on Whole House Electrical Load?

My house has a relatively small 100A breaker, and I am hesitant to install a full 50A 240v charger because it's possible the main breaker could be overloaded if I'm charging my car, doing laundry, and cooking - for example. Of course, most of the time I'm not doing those things. Is there any way to get a current sense coil external to the Open EVSE hardware to limit charge current? I could attach it to one of the incoming legs at my main breaker panel, and the charger could then use full current any time the sensed current on those legs is <80A, reducing current if it goes over down to some minimum value (8A?). That would let me get full charge current most of the time without worrying about popping the mains.

Anyone else heard of this or tried this?

You sure can. OpenEVSE and Open Energy Monitor integrate very well. Check out this blog for Solar diversion. The exact same concept could be used to limit your house hold draw.

Ah ha! So the EVSE and the Open Energy Monitor connect via WiFi? Is that typically reliable enough? Would be nice to have a hard wired sensor so current limiting doesn't rely on my internet service.

You can also connect OpenEVSE via Serial to the OpenEnergyMonitor EmonPi.

Here is more information and the source materials, plus advantages of different archetectures.

OK, with the usual caveats vis a vis the Open EVSE enclosure - looks like the serial lines would need to be 600V rated to ride in conduit with the power, and then they monopolize the circuit that otherwise WiFi would plug into?

Anyway, looks like this could be interesting either way. Thanks very much.

Do you know if the 100A limitation on the current sensor is the sensor, or the EmonPi?

"WiFi" is not the same as "internet." You can have fairly strong control of your home WiFi infrastructure if you choose.  In particular, you can establish a completely separate WiFi WAP for your critical devices ant connect them to it instead of connecting them to your "normal" WAP. You can then connect that WAP via a wired LAN to the rest of your intranet, or not, or connect it via a firewall. I am unfamiliar with the details of the OpenEVCS and EmonPi, but if these have USB connections and opensource software, you can also choose to us wired LAN via a USB Ethernet dongle instead of WiFi, and again use a separate LAN with or without a firewalled connection to your intranet.


OK, makes sense.

Has anyone tried a >100A sensor? Not sure these will fit around the 1AWG aluminum conductors coming into my house.

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