Electronics > Power/Renewable Energy/EV's

AC whole house battery charging based on grid-tied solar output and mains load

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dlarue:
Our solar PV system is soon to be switched to NEM 3.0( So CA ) in Jan 2025 and I'll be building 1 or 2 15 kWh LFP packs to get us through the 4p-9a no/low solar periods.  I'm looking for a programmable 48V charge controller which would only charge the battery packs from AC power when the solar/micro-inverters are producing and programatically limit backfeeding.

With the charge controller programmable for something like setting the AC charge controller to limit the grid to seeing a 10W backfeed with the rest charging batteries. Like a zero export inverter but for battery charging.

Also would need a whole house inverter(3 kW) which would then take over the household load as the solar PV generation waned but allowing for the grid seeing a load of only 10-100 W through the evening, night and early morning no/low solar periods.

From what I've seen, solar PV charge controllers want direct DC solar input. Am AC based charge controller system which monitors only solar inverter AC power flow and the mains panel lines while having the ability to adjust the battery charging according according to solar PV output and household loading could bolt onto any existing home grid-tied system. And do so without going onto or touching the thousands of existing grid-tied solar installations.

The clock is ticking so looking for solutions since the CPUC and the CA IOUs own us otherwise.

dlarue:
It's looking like nobody makes a zero export based solar battery charger. At least not a battery charger which is based on AC power input and uses monitoring of AC power from solar PV inverters and house load(mains) monitoring to regulate battery charge rates.

My next step is to look for an AC based battery charger with an open control API so I can do my own solar PV output and house load monitoring and command the charger appropriately.

NiHaoMike:
How about an Open Energy Monitor ( https://openenergymonitor.org ) along with hacking some surplus "telecom rectifiers" with ESP32 or similar to allow them to limit output current? Note that unlike a zero export inverter, it doesn't actually need to prevent export and therefore a response time of a few seconds would be acceptable. (In practice, it would not be hard at all to get the response time to a few 10s of milliseconds.)

rteodor:
Not sure I fully understand, but since you need an inverter anyway why not get one with charger included ? Victron Multiplus or the like.

dlarue:

--- Quote from: rteodor on July 11, 2024, 08:36:25 am ---Not sure I fully understand, but since you need an inverter anyway why not get one with charger included ? Victron Multiplus or the like.

--- End quote ---

I've not yet looked at inverters yet but since they expect DC connections to the solar PV modules I figured they would not work limiting backfeeding of the grid by the AC connected inverters.
I'll look at inverters to see if any have power flow sensing for battery charge control. Thanks for the feedback.

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