DIY additional storage to on-grid Enphase Encharge

[Spamurai]

Have a fully functional Enphase Encharge battery system with two of the 10T batteries, solar panels of course. Location is NorCal in PG&E territory. My installer advised me I could only have two of the Encharge 10T batteries (20 kWh total). This is not an Enphase technical limitation, I think its a PG&E SGIP limitation as, pre-EV, I could not document sustained loads over 12kW. Enphase batteries are great, but the $/watt isn't competitive and I won't add more. Note large ranch style property with outbuildings in a wildfire shutdown zone.

Goal, harness solar production during the day and zero out (peak-shave) the evening Time of Use rates.

Proposal: AC couple a sufficient spec on-grid smart inverter with an additional battery storage.

• Inverter and storage must be located on a subpanel in an outbuilding. Space not available near the main panel.
• Inverter needs to "play well" with Enphase Enpower micro-grid, so UL1741SA. Other considerations ? Inverter will be located "downstream", that is as part of the microgrid.
• Inverter can either function on existing Enphase microgrid and with existing Enphase batteries during a power outage / grid disconnect, or it must shut itself down. Obviously prefer it to run.
• Baseline consumption is ~2kW for house, pool, workshop and network equipment. I can grab real-time consumption data from Rainforest Eagle and/or Enphase, or even insert another IOTAwatt to dynamically adjust the grid-feed of the inverter. Since my goal here is electrical safety, let's assume I just program the smart inverter to "sell" 2.5kW / hour from 3 pm until midnight, and charge batteries from 10 am until done.

Details:

• Inverter will NOT have solar panels installed. Outbuilding is fully shaded. Inverter doesn't need MPPT charger. Also skip the AC coupling 1:1 rule ?
• No plan to put load directly on inverter. Inverter installation is essentially removeable.
• Inverter needs to be capable of working safely with US 60Hz 240v output into a subpanel with a 125A breaker. Suggest sizing the inverter to 5~8kW on appropriate sized breaker, as the goal is to offset peak consumption rather than run the entire house.
• Inverter and batteries need to be UL listed, prefer closed-loop BMS.
• Evaluating Fortress Battery eFlex 5.4 and Victron Hybrid inverters.
• Experience: I'm a systems engineer during the day, have some residential electrical experience and a licensed electrician on standby to assist the project.

So, can this be done safely ? Any recommendations on inverters ?

 

[Spamurai]

Diagram of the proposed DIY powerwall.

 

[zanydroid]

To be frank, there’s a few inconsistencies/things I don’t understand about your goals and assumptions. It’s possible I’m biased towards a different property type and microclimate (I’m also located in Northern California but on a SFH lot in a town on the peninsula)

Evaluating Fortress Battery eFlex 5.4 and Victron Hybrid inverters.

Where did you see that this is a UL9540 listed combo? I thought Victron only has a limited number of UL1741 inverters. I believe Fortress has UL9540 paired inverters.

If you get one of those paired combos then it is safe in the sense that it satisfies California residential code.

I don’t believe it’s easy to break even under summer PG&E TOU rates with UL9540 batteries. I ran some numbers with batteries with only UL9540A (IE not good enough for residential install) and it wasn’t good either. The spread between peak and off peak in the summer with regular TOU is a little over $0.10 IIRC

You may end up running inverter output in parallel with PG&E which requires their permission. The inverter power “pushes” all the way out to your service, hybrids can be presumed to be bidirectional on their AC “input” port

Victron is not on CEC list when I checked recently, and the most recent NRTL testing cert victron got for UL1741 makes no mention of SA nor SB.

With your wiring diagram you need remote CT support to limit backfeed to PG&E. AFAIK the supported limiter input on hybrids are either internal CT, remote CT connected via analog wires, or remote CT connected over serial bus, rather than the consumption measuring things you mentioned.

Are you trying to avoid draining your Enphase during peak shaving? Your 20kWh Enphase is enough to achieve 2kW sell from 3-midnight already. Also sounds like you are trying to do EV2A with the desire to sell until midnight… EV2A with battery didn’t seem like a good alternative to TOU for me under the assumption I already generate enough power for annual consumption under NEM2, and most usage in winter instead of summer.

 

[svetz]

Batteries are expensive right now, the upcoming sodium battery is expected to be less than $80/kWh.

As you're Enphase, if you can wait a year, this might suit you: https://diysolarforum.com/threads/enphase-bidirectional-charging.56224/,
it allows your EV to become a house battery.

If you can't wait, you might find this of interest: https://diysolarforum.com/threads/adding-an-ess-to-enphase-enlighten-system.42737/

 

[DER Solar]

UL1741 SA and SB supplements are for the grid provider or generator, they do not apply for the micro-grid generator! It's one-way only!

Enphase uses direct power controls to adjust PV power, they are proprietary and not accessible for integrating other backup solutions. And they kick other inverters of the micro-grid. The only way to AC couple any inverter to the Enphase AC backup bus is with direct power controls that measure backup load and SOC. Todd D from NC Solar Electric has AC coupled Hoymiles inverters to Enphase backup by modulating DC input to the AC coupled non-Enphase inverters.
I'm collaborating with Todd, but trying to do direct power control via ModBus with Schneider XW Inverters. Have successfully AC coupled Hoymiles HMS-2000 to Schneider XW + and XW Pro inverters. Now working on ModBus direct power controls. Unlike Enphase, Hoymiles microinverters are SunSpec certified and committed to open standards! You also need a charger to re-charge the additional batteries

 

[Consumerbot3418]

The only thing I can say with certainty is that Victron, as of now, doesn't have a product you can use. They don't support backfeeding in the US at all (no "grid code").

I'm actually using Victron equipment to do something similar to what you wanted: leverage additional battery, and in my case, provide some additional redundancy to my off-grid system.

I'd hoped to switch the input to the Victron inverters between my off-grid setup and the utility, but I don't have Victron's special UL-certified inverters, and my utility wants me to go through the net metering approval process before allowing any inverter connection, even if there's no PV attached.

 

[zanydroid]

I am aware of Victron’s certification status and don’t plan to operate it in parallel with grid

 

[Gubman]

...

 

[Gubman]

Have a fully functional Enphase Encharge battery system with two of the 10T batteries, solar panels of course. Location is NorCal in PG&E territory. My installer advised me I could only have two of the Encharge 10T batteries (20 kWh total). This is not an Enphase technical limitation, I think its a PG&E SGIP limitation as, pre-EV, I could not document sustained loads over 12kW. Enphase batteries are great, but the $/watt isn't competitive and I won't add more. Note large ranch style property with outbuildings in a wildfire shutdown zone.

Goal, harness solar production during the day and zero out (peak-shave) the evening Time of Use rates.

Proposal: AC couple a sufficient spec on-grid smart inverter with an additional battery storage.

• Inverter and storage must be located on a subpanel in an outbuilding. Space not available near the main panel.
• Inverter needs to "play well" with Enphase Enpower micro-grid, so UL1741SA. Other considerations ? Inverter will be located "downstream", that is as part of the microgrid.
• Inverter can either function on existing Enphase microgrid and with existing Enphase batteries during a power outage / grid disconnect, or it must shut itself down. Obviously prefer it to run.
• Baseline consumption is ~2kW for house, pool, workshop and network equipment. I can grab real-time consumption data from Rainforest Eagle and/or Enphase, or even insert another IOTAwatt to dynamically adjust the grid-feed of the inverter. Since my goal here is electrical safety, let's assume I just program the smart inverter to "sell" 2.5kW / hour from 3 pm until midnight, and charge batteries from 10 am until done.

Details:

• Inverter will NOT have solar panels installed. Outbuilding is fully shaded. Inverter doesn't need MPPT charger. Also skip the AC coupling 1:1 rule ?
• No plan to put load directly on inverter. Inverter installation is essentially removeable.
• Inverter needs to be capable of working safely with US 60Hz 240v output into a subpanel with a 125A breaker. Suggest sizing the inverter to 5~8kW on appropriate sized breaker, as the goal is to offset peak consumption rather than run the entire house.
• Inverter and batteries need to be UL listed, prefer closed-loop BMS.
• Evaluating Fortress Battery eFlex 5.4 and Victron Hybrid inverters.
• Experience: I'm a systems engineer during the day, have some residential electrical experience and a licensed electrician on standby to assist the project.

So, can this be done safely ? Any recommendations on inverters ?

Take a look at:
https://diysolarforum.com/threads/h...-xw-pro-6848-w-rack-batteries-off-grid.50433/.
and

Enphase IQ8+ AC coupled to Dual Schneider Conext XW Pro - No PV when off grid

I have this system all setup. In Grid tied mode everything works great. There is a problem getting the PV inverters to turn on after disconnecting from the grid. I saw a similar post from someone trying to make this work with a Solark. The system runs fine on batteries, but the whole point...

diysolarforum.com

I'm in a similar boat. The thread will expose you to a variable mix of participants contributing to the same goal.