Adding "solar generator" batteries to grid tie PV system

**sdold** · 01-31-2024, 04:22 PM

Hi Telero, welcome to the forum. Sorry your post didn't appear right away, the link automatically put it into "moderation" status, but you should be good to go now.

**Mike 134** · 01-31-2024, 04:59 PM

Originally posted by telero

Found another thread similar to what I was looking for, but the general advice seemed to be to get a fossil fuel powered generator. https://www.solarpaneltalk.com/forum...backup-battery. Not what I'm looking for. Here is my situation questions:

I have a 12.42 kW grid-tie system with SolarEdge SE10000H (not home hub) inverter. I'd like to add batteries that I can use and charge from solar excess during grid outage. I am completely fine with having to manually switch to battery backup. Ideally the system would work as follows:

Power goes out
Turn off non critical breakers
Turn off main breaker
Move generator interlock and turn generator circuit on
Power on battery system

What I'd also like from this system and that I've been trying to search for, but maybe failing to use the right terms is:

When on battery, solar inverter will power on
Solar to provide as much required power as possible to loads
Additional power provided by battery when solar output less than load or solar unavailable
Battery to be charged by solar when solar output is more than load and battery is not full

I'm curious if this is possible (even if not recommended), and am thinking I'm just missing terminology to find the pieces that I might need.

I'm focused on a setup that would allow batteries that could potentially be portable (or at least a small amount of a larger expandable system), or potentially be used with V2G at a later point in time.

From what little I know about Solar Edge if it's not an inverter made to work with batteries the inverter shuts off with a power failure. It needs to see the power grid to operate.

**Ampster** · 01-31-2024, 05:16 PM

Originally posted by telero

............
When on battery, solar inverter will power on
.......

A grid tie inverter will not power on in the absence of the grid or a hybrid inverter which has AC coupling capabilities. Your solar generator will not do that. For more information research "AC coupling"?

**telero** · 01-31-2024, 05:33 PM

So the "solar generator" batteries have their own inverter to output AC. If that AC is not the correct thing to trigger the SolarEdge inverter, then is the hybrid inverter mentioned going to be the device that would go in between the solar generator and the SolarEdge inverter? I would think another inverter would be wanting DC from another set of PV panels or from batteries directly. Unless it also has its own AC generator input, but then it wouldn't really be acting as an inverter, would it? Is there another device instead of a full inverter that would take the AC from the solar generator and activate the SolarEdge?

**solardreamer** · 01-31-2024, 06:44 PM

Originally posted by telero

Is there another device instead of a full inverter that would take the AC from the solar generator and activate the SolarEdge?

The issue is not activating your SE inverter. Any "solar generator" or power station with stable pure sine wave 240V output can directly activate your SE inverter. The problem is that solar inverters are designed to always push out max power available from the solar panels. As soon as there is not enough loads to consume all solar power the extra solar power will flow to the power station and trip and/or damage it very quickly (can be a fraction of a second).

**Ampster** · 01-31-2024, 06:50 PM

I sounds like you are looking for a simple answer and AC coupling is complicated. It is not just a matter of something "activating" the GT inverter. The GT inverter goes through a boot up process which runs through several tests to verify that the connection behaves like the grid. It involves UL standards which the AC generator is not capable of meeting and therefore the AC generator is not capable of AC coupling. It also involves DC batteries powering the hybrid and the hybrid using frequency shift to enable the GT inverter to be managed as loads shift. Does any of what i said resemble what you discovered when you researched AC coupling?

**telero** · 02-01-2024, 09:59 AM

The ability to turn off the solar generation when the overall load isn't enough was something I hadn't been considering. But once I started using AC coupling in my searches, I did find a video that talked about pretty much what I'm looking for, but it involved another inverter. Looks like SolArk can do everything I want, but it is a little more complicated than I was originally envisioning. Seems like adding a SolArk or just upgrading the SolarEdge that I already have are the best options. Thanks for helping me find the parts that I was missing.

**Ampster** · 02-01-2024, 12:37 PM

I use a SolArk and AC couple it with 8kW of Enphase IQ7 micro inverters. In your case 12kW of GT inverter capacity is a lot of power for a hybrid inverter to manage. You may need to dive into the specs of the SolArk and others to see how many kWhs of batteries you may need as a buffer to successfully AC couple that much power from your GT inverter. It is not an issue when the grid is up because the grid acts as a buffer. The grid has almost infinite capacity to buffer any changes in loads and absorb the balance of the output of your GT inverter.

I previously had an Outback inverter AC coupled to a SolarEdge HD inverter at another home. I do not know the details but I have heard there is an upgrade to some SolarEdge GT inverters which allows them to operated with batteries. You should also think about which loads are critical when the grid is down and plan accordingly to move those circuits to a critical loads panel. In addition to providing back up my SolArk works every day to provide power so that I do not pay the high rates for energy during peak rate periods in California. That is why a hybrid inverter can improve the ROI of an existing solar system, if you are in an environment with high Time of Use rates. A generator cannot do that.

**solardreamer** · 02-01-2024, 12:57 PM

Many hybrid inverters can do AC coupling in addition to SolArk ... Schneider, Victron, Magnum, Outback, ... all have pros and cons and none are cheap especially with the required batteries. Best to do more research before picking one.

**Ampster** · 02-01-2024, 01:21 PM

Originally posted by solardreamer

Many hybrid inverters can do AC coupling in addition to SolArk ... Schneider, Victron, Magnum, Outback, ... all have pros and cons and none are cheap especially with the required batteries. Best to do more research before picking one.

I could not agree more..Every use case is different and research is critical to finding an optimal solution..

Adding "solar generator" batteries to grid tie PV system

Adding "solar generator" batteries to grid tie PV system

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