DIY PowerWall with minimal infrastructure? ( V2H )

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Supersleeper

Well-known member
Joined
Aug 7, 2017
Messages
124
Location
SF Bay Area
Forgive me if this seems crude and lacking detail. Reading the specs of my Enphase M215, I can run 8 in series (48v max DC in) to have 360v DC out from my CHAdeMo port to continue grid power until Tier 2 drops off at about 11:00pm, then disengage CHAdeMo port for LVL 2 charging back into the Leaf until the Tier 1 picks back up at 8:00am. I'm curious if it would need a load resister to lower amperage? If doable, most of this should be able to be done with only a few things I can think of:

1. CHAdeMo interface and cable
2. CAN bus communication device and timer (Arduino?)
3. High-voltage relay systems to switch DC from roof PV parallel system to Leaf in-series CHAdeMo interface.
...OR...
3. Re-wire 8 of my PV into series with 8 x series M215 micro controllers and put Leaf CHAdeMo DC directly in parallel.
4. Appropriately gauged cabling and distribution blocks.
5. Circuit breakers?

I might just sound crazy, but seems I already have much of the infrastructure needed to do this.
 
You would need to tap your leafs battery internally for 48v blocks, you can't run emphases as additive current sources
 
The DC input to the Enphase M-series inverters is the input to a power converter. In the case of the M215s, I believe it is the input to a DC-AC inverter and in the case of the M215IGs, it is the input to a DC-DC converter. This input does not have a specified DC impedance because, in fact, the input impedance varies drastically between a near-open circuit to a near-short circuit. This allows the power converter to actively change its input impedance in order to find and operate at an appropriate point on the I-V characteristic of the PV module which is attached. As a result, it is not possible to attach the DC inputs of M-series inverters in series and expect them to split the voltage evenly. Whichever one has the highest impedance first will exceed its maximum voltage limit and will then experience voltage breakdown. If it fails as an open circuit, it *may* protect the other units from catastrophic failure. If it fails as a short circuit (power MOSFETS sometimes fail this way, or there could be a thyristor "crowbar" circuit in place on the input that will create a short in case of an overvoltage), then they will all fail in rapid succession.
 
RegGuheert said:
The DC input to the Enphase M-series inverters is the input to a power converter. In the case of the M215s, I believe it is the input to a DC-AC inverter and in the case of the M215IGs, it is the input to a DC-DC converter. This input does not have a specified DC impedance because, in fact, the input impedance varies drastically between a near-open circuit to a near-short circuit. This allows the power converter to actively change its input impedance in order to find and operate at an appropriate point on the I-V characteristic of the PV module which is attached. As a result, it is not possible to attach the DC inputs of M-series inverters in series and expect them to split the voltage evenly. Whichever one has the highest impedance first will exceed its maximum voltage limit and will then experience voltage breakdown. If it fails as an open circuit, it *may* protect the other units from catastrophic failure. If it fails as a short circuit (power MOSFETS sometimes fail this way, or there could be a thyristor "crowbar" circuit in place on the input that will create a short in case of an overvoltage), then they will all fail in rapid succession.

OK, this makes more sense to me. Thanks for explaining that. So apparently there's no way to do this without some expensive components for step-down from 360v to 40v.
 
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