Battery Storage with Micro Inverter System

[alferz]

I have an 8kw system with enphase microinverters installed about 2016. It is under a 20 year PPA agreement so I really cant modify the system. The system ties into my main panel via a 2 pole 40 amp breaker. The main problem Im trying to solve is I want to add a battery backup to the system that will allow the panels to continue generating power and charging the batteries when the grid is down. Right now they use anti-islanding and shut down during grid failures.

What kind of inverter would i need to be able to supply 120vx2 power to the micro inverters to trick them into producing power?

 

[ncsolarelectric]

You need an Enphase IQ Battery 3T, an IQ System Controller 2, a cellular modem, and an Enphase storage-certified installer. Otherwise, you'll void your Enphase warranty.
An off-grid system requires a transfer switch. You don't have that in your existing system. If you try to trick the inverters to operate when the grid fails, it can cause death for linemen working to repair the lines.

 

[alferz]

Thanks, I realize the importance of in anti-islanding (im not a line worker but i work with them). Any other options than going all Enphase? Although the existing system is Enphase, I really dont want to modify it in any way, or have to obtain permission from the PPA provider. The battery system I was envisioning would have some kind of ATS to disconnect from grid in an outage, and feed into another breaker on the main panel to switch over to backup power automatically, supplying split phase power to the panel so the micro-inverters could operate. The next best thing would be an off grid inverter with a critical loads subpanel, but then I have 8kw of solar that is sitting there unused in an outage. If I owned the system I would probably switch to a DC coupled system and a grid tied inverter but Im pretty much stuck with this for 14 more years. In the meantime Im hoping to gain some form of battery backup that can be re-generated from the panels in an extended outage.

 

[ncsolarelectric]

You assume you can connect to the main panel without affecting your existing system. That won't work without the Enphae System Controller 2. You can use any battery inverter and a sub-panel, such as an EG4 3kW or an AIMS Power inverter with a built-in transfer switch. Then relocate your critical loads to the sub-panel. That's how it's done.

 

[DER Solar]

I have an 8kw system with enphase microinverters installed about 2016. It is under a 20 year PPA agreement so I really cant modify the system. The system ties into my main panel via a 2 pole 40 amp breaker. The main problem Im trying to solve is I want to add a battery backup to the system that will allow the panels to continue generating power and charging the batteries when the grid is down. Right now they use anti-islanding and shut down during grid failures.

What kind of inverter would i need to be able to supply 120vx2 power to the micro inverters to trick them into producing power?

Do you want to install it yourself or have a certified installer do this?
In case you do it yourself and settle on Enphase, you need to take all Enphase courses and get certified, time consuming, especially the last part where you have to design a backup system and submit it for review
.
Depending on the single highest circuit load you want to have backed up, you have to match this one load with an equivalent Enphase stack of inverters/batteries. That can get very expensive!

My advice: limit the highest backup load and leave all non-critical loads on the existing main panel.
Don't try to do an MPU (master panel upgrade) unless your panel is old or you need whole-house backup, it gets very expensive.
Talk and get bids from different backup solutions providers! And stay with what you have, many companies try to persuade you to install new panels and new micro-inverters!

You may want to inquire about FranklinWH, their backup system works well with all Enphase and other microinverters and PV string inverters, but all of the ready-to-go backup solutions are expensive. Try to find a system where you can stack inverters and batteries independently depending on what your needs are. There aren't many choices yet, but they'll come to market this year.,

Todd D is an expert and can give you a different perspective, especially if you want to do it yourself or a portion of it.

 

[DIYrich]

Should be able to use a Sol-ark. You can keep it as load connected solar as long as you never use a generator. Sol-ark will connect between your main grid connect and main panel. Batteries connect to the Sol-ark directly.

The reason you can't use a generator is that when the generator is running, the sol-ark can't reduce the output of the solar, and you may backfeed the generator.

 

[cs1234]

To go with somebody other than Enphase (which I certainly can't blame you on), you need to install an inverter than can do AC coupling to the enphase micros, like a Sol-Ark or Schneider.

 

[alferz]

What I ended up putting in was a 13.2 KWh 8s2p LiFePO4 battery pack coupled with a Victron Multiplus II 2x120v. I reconfigured my critical circuits to run on a dedicated critical loads subpanel fed from the Multiplus II. When grid power is available the MP-II can put out 40a (20a battery + 20a AC) of single phase power. Technically the 2x120 can put out 2 phases when grid power is up, but you lose the second leg in power outages. So for me, I just use it single phase all the time and dont have a backup plan for 2 phase appliances like AC, Oven, and pool equipment. Side benefit is, I can charge my pack at night at discounted utility rates (which beat the rate I pay per KWh to the Solar PPA Vendor) and use those electrons during the day to offset about 5KW a day to those critical loads. When grid is down, the unit automatically fails over to battery (fast enough where even a PC running on that protected circuit will not get reset by the failover). The unit can output 20a max in battery only mode, which is more than sufficient for the basic loads I have on these circuits (2 refers, a tankless water heater, natural gas furnace, network/media equipment, a couple lights/outlets). I can run these limited loads for about 3 days with the pack I'm using.

Would love to use a Sol-Ark or other grid-tied inverter with battery inputs, and on a future house I will definitely install one. The tricky thing here is I'm signed onto this Solar PPA ($0 upfront and you pay for KWh produced for 20 years) that restricts any modifications to the solar panels, inverters, and the grid-tie for 20 years (these are, by the way terrible deals, please do not sign one). So I really could not have tied directly into the panels in my case.

Paired with a generator or solar panels the MP-II could work great for long term outages too. You will never power your whole house from it. But my theory is, I dont want my whole house backed up anyway. That will just encourage the family to use as much power as they were before an outage. Even the largest powerwall will soon be quickly depleted with Grandma cooking a turkey in the oven with the AC set to 68 ?. Even if you dont have panels (or you dont own them, like me), the MP-II its a great solution for those shorter term 2-10 hour power outages that seem to be pretty common throughout the year. Your pack and circuits just need to be sized right to your needs.

 

[etcm]

Do you want to install it yourself or have a certified installer do this?
In case you do it yourself and settle on Enphase, you need to take all Enphase courses and get certified, time consuming, especially the last part where you have to design a backup system and submit it for review
.
Depending on the single highest circuit load you want to have backed up, you have to match this one load with an equivalent Enphase stack of inverters/batteries. That can get very expensive!

My advice: limit the highest backup load and leave all non-critical loads on the existing main panel.
Don't try to do an MPU (master panel upgrade) unless your panel is old or you need whole-house backup, it gets very expensive.
Talk and get bids from different backup solutions providers! And stay with what you have, many companies try to persuade you to install new panels and new micro-inverters!

You may want to inquire about FranklinWH, their backup system works well with all Enphase and other microinverters and PV string inverters, but all of the ready-to-go backup solutions are expensive. Try to find a system where you can stack inverters and batteries independently depending on what your needs are. There aren't many choices yet, but they'll come to market this year.,

Todd D is an expert and can give you a different perspective, especially if you want to do it yourself or a portion of it.

I thought the whole home backup inserted the Enphase controller contacts between the grid meter input and the main panel input breaker; and with that assumption, why would there be a need to do an MPU if your panel was older, but perfectly serviceable?

 

[DER Solar]

Every home is different and the priorities for backup-loads and non-backup loads are different. If the main panel is good, you're right. An MPU upgrade is expensive.
The IQ system controller has no pre-MID feed-through for non-backup loads - unlike Powerwall or FranklinWH - so all your loads need to be on the backup side. What do you do if there are loads that don't need to be backed up?
And per NEC, the maximum AC circuit breaker for an Enphase backup system cannot be greater than 50A!

 

[etcm]

Every home is different and the priorities for backup-loads and non-backup loads are different. If the main panel is good, you're right. An MPU upgrade is expensive.
The IQ system controller has no pre-MID feed-through for non-backup loads - unlike Powerwall or FranklinWH - so all your loads need to be on the backup side. What do you do if there are loads that don't need to be backed up?
And per NEC, the maximum AC circuit breaker for an Enphase backup system cannot be greater than 50A!

Thank you. Is this 50A limit a maximum AC (source) limit? Is this the amount of AC bkr from Enphase to the load panel?
My Enphase installer just told me I needed to do a MPU and i do not know why ( awaiting tech response now.) Between his first visit and the last visit, I had a inverter start heat pump installed .. but the air handler ( my furnace system had a 120v air handler) has a 60A 240VAC breaker. I already had the AC tech disable the 10kW backup resistive heater ( it also defrosts the coil if needed.) I live in SW Florida and will probable never need to de-ice my outside coil. If backup heat is needed, I have a gas oven/range that has over 100k BTU out. If they say the 60A bkr is the deal breaker, I'll change itvout for a 50A or less ( I have new 40 and 30 amp ones now) the AH fan only draws about 1.2kW under full load.

 

[ncsolarelectric]

The AmenSolar 5, 8, and 10kW Hybrid Inverters have a generator input, as well as a grid input, an output for critical loads, and an output for non-critical loads. It just doesn't have all the circuit breakers that the Sol-Ark has. It also has UL1741SA, and IEEE-1547, so it should be able to AC couple to Enphase or any other inverter that meets those standards.

 

[etcm]

Thank you. Is this 50A limit a maximum AC (source) limit? Is this the amount of AC bkr from Enphase to the load panel?
My Enphase installer just told me I needed to do a MPU and i do not know why ( awaiting tech response now.) Between his first visit and the last visit, I had a inverter start heat pump installed .. but the air handler ( my furnace system had a 120v air handler) has a 60A 240VAC breaker. I already had the AC tech disable the 10kW backup resistive heater ( it also defrosts the coil if needed.) I live in SW Florida and will probable never need to de-ice my outside coil. If backup heat is needed, I have a gas oven/range that has over 100k BTU out. If they say the 60A bkr is the deal breaker, I'll change itvout for a 50A or less ( I have new 40 and 30 amp ones now) the AH fan only draws about 1.2kW under full load.

Ok, I just read the Enphase line..the output of the battery backup inverters must be enough power the largest breaker - the Enphase controller is max'ed out at 50A. So, it looks like I will replace my 60A breaker with a 30A breaker

 

[DER Solar]

The reason is the total inverter output power in backup mode. The max inverter limit - 3.84 * 4 = 15.4 kw for 4 Enphase 10 T units - determines the max breaker size for a single load, NEC rules for backup systems. A lot of Enphase users trip up on this limitation. You do have similar limitations with Powerwall, FranklinWH or Schneider XW Pro's, but they are much higher, as high as you can stack the inverters/batteries. Your only remedy is to down-size the breakers/loads above 50A.

 

[wheisenburg]

Should be able to use a Sol-ark. You can keep it as load connected solar as long as you never use a generator. Sol-ark will connect between your main grid connect and main panel. Batteries connect to the Sol-ark directly.

The reason you can't use a generator is that when the generator is running, the sol-ark can't reduce the output of the solar, and you may backfeed the generator.

I believe you are correct about this.

I keep trying to tell people on here that you can't run AC coupled solar in parallel with a generator. They keep telling me I am wrong and that if you just turn on the "No Sell" option and hook the generator to the grid input on the inverter it will not back feed the generator. This will work for DC coupled solar because they can control the DC in to match the loads.

I believe what actually happens when running on a 60 HZ generator is that your AC coupled solar will run at 100% output. Once the batteries are full there is no place else for that power to go. This seems obvious to me. Why are so many people misinformed on this? It is like they believe there is a "Magic Electron Director" inside the inverter routing electrons to the correct destination. In fact all they have is an AC bus. The only thing they can control is how much AC coupled current is diverted to the battery and how much DC current comes in from the charge controllers. Once a generator or the grid is feeding the system it becomes the clock and frequency shifting doesn't work. For the grid this is fine. All that excess solar will flow out to the grid. The exact same thing will happen when you are on a generator. Obviously when you start to back feed thousand of watts into the generator, bad things will happen.

 

[DIYrich]

With the sol-ark, if you put the generator on a transfer switch with the Grid, (generator on grid input) and put the AC PV on the Gen Input Line, then it can work. It will disconnect the AC PV if there is risk of backfeeding the generator.

 

[wheisenburg]

With the sol-ark, if you put the generator on a transfer switch with the Grid, (generator on grid input) and put the AC PV on the Gen Input Line, then it can work. It will disconnect the AC PV if there is risk of backfeeding the generator.

I agree with that, but then you are no longer running the AC PV in parallel with the generator. I've seen people planning to do this with the Gen on the grid in and AC coupling the PV into a critical loads panel.

With my Schneider I have the Gen on the AC2 in (which is their Gen Input). Then I have the PV AC coupled in their power distribution panel to the inverter out. This is what goes out to the loads. With Schneider they tell you must install a mutual exclusion contactor so that you can not have the PV and the gen connected at the same time. Basically it is a 4 pole contactor with 2 NC and 2 NO contacts.

I may end up using this contactor more as a way of turning off the PV to prevent over charging. Then I will use a DC coupled charger off a small generator. Probably the EG4 chargeverter. I plan to install some small control relays to turn on the PV when if the grid is up or the voltage is lower than a certain amount. I have about 10 KW of AC coupled PV. I need to make sure it doesn't try to pump huge amounts of current into the batteries when they are fully charged

 

[DIYrich]

I agree with that, but then you are no longer running the AC PV in parallel with the generator. I've seen people planning to do this with the Gen on the grid in and AC coupling the PV into a critical loads panel.

Not the way to do it. The PV goes into the Gen Input, not into the Critical Loads panel. Sol-ark can disconnect the Gen Input. It can't disconnect the critical loads panel.

AC PV from the Gen Input can be in parallel with Generator Input on the Grid Line.

 

[etcm]

Every home is different and the priorities for backup-loads and non-backup loads are different. If the main panel is good, you're right. An MPU upgrade is expensive.
The IQ system controller has no pre-MID feed-through for non-backup loads - unlike Powerwall or FranklinWH - so all your loads need to be on the backup side. What do you do if there are loads that don't need to be backed up?
And per NEC, the maximum AC circuit breaker for an Enphase backup system cannot be greater than 50A!

A year later .. I was told that due to the Enphase Control panel connecting to the meter, IT was now classified as the "main panel" and my current home main panel would then be a subpanel to the Enphase box. They had to get a separate permit for the "main panel" work and one for the solar install up to the enphase controller box.

 

[wheisenburg]

AC PV from the Gen Input can be in parallel with Generator Input on the Grid Line.

This is from Sol Arc:

@Sol-Ark
1 year ago
Hi Harvey, these are awesome questions for our solar engineering team, and I'd definitely start a conversation with them through this link: https://www.sol-ark.com/contact-us/
With that in mind, here's a couple of answers that may help clarify your situation:If you have a 16kW system, and you're adding 23kW more, you'd be right at 39kW PV. Each 15K can take 19.5kW PVdc, so 39kW with two systems in parallel. You can connect different brands of panels, just not recommended on the same MPPT, as voltages across the MPPT should be the same. Each 15K has 3 MPPT's, so you should have some room to change the cabling to make it make sense. Adding a larger generator is fine, as the 15K will not take more power than needed. Also, each 15K can take up to 24kW of a generator, so if you are paralleling the generator to both 15K's you should be within specs. "Since I have two 15k sol ark inverters, is it possible to connect my whole house generator to the Gen lug on one 15k sol ark inverter and AC couple my solar edge inverter on the Gen lug on the other 15k sol arc?" No. Not if you're running the systems in parallel. I'd contact solar engineering for more help on system design. The 15K's also have a two-wire start for automatic generator battery charging, and "My concern is that I don't want my generator to turn on when the grid goes down if I still have enough solar power and battery to run my needs," the generator charging voltage setpoint will take care of charging the battery from the generator as soon as the batt voltage reaches the predefined setpoint. Hope this helps. Again, I highly encourage you to reach out to the solar engineering team. -Bernie


I could find nothing from Sol Ark saying it was OK to run AC coupled PV in parallel with a whole home generator. Now they may have some programming that automatically shuts off the AC coupled solar on the Gen input when a stand by generator starts up. If so that would be OK. If these items are ever directly connected together smoke will occur. They are NOT very good about warning people about this issue. If you look at Sol Arcs designs, where you use AC coupled PV on the Load side, they have a "Do NOT use" warning on the Generator input.