Supersleeper
Posts: 60
Joined: Mon Aug 07, 2017 10:04 am
Delivery Date: 06 Aug 2017

DIY PowerWall with minimal infrastructure? ( V2H )

Fri Aug 25, 2017 7:23 pm

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.

rmay635703
Posts: 400
Joined: Wed Jan 19, 2011 7:43 pm

Re: DIY PowerWall with minimal infrastructure? ( V2H )

Sat Aug 26, 2017 8:10 am

You would need to tap your leafs battery internally for 48v blocks, you can't run emphases as additive current sources

Supersleeper
Posts: 60
Joined: Mon Aug 07, 2017 10:04 am
Delivery Date: 06 Aug 2017

Re: DIY PowerWall with minimal infrastructure? ( V2H )

Mon Aug 28, 2017 10:35 pm

rmay635703 wrote:You would need to tap your leafs battery internally for 48v blocks, you can't run emphases as additive current sources


How would the modules know? It's just a DC current.

User avatar
RegGuheert
Posts: 5522
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: DIY PowerWall with minimal infrastructure? ( V2H )

Tue Aug 29, 2017 6:56 am

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
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

Supersleeper
Posts: 60
Joined: Mon Aug 07, 2017 10:04 am
Delivery Date: 06 Aug 2017

Re: DIY PowerWall with minimal infrastructure? ( V2H )

Tue Aug 29, 2017 12:02 pm

RegGuheert wrote: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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