Good Day

I have an existing grid-tie setup and would like to add a battery bank without losing my grid-tie functionality. Can someone please assist on most cost effective way this can be done.

Existing grid-tie setup:

14 x 330w Renewsys Mono panels

1x Omniksol-5k-3P-TL2 Grid-tie only inverter

 

I have received the following from a friend that emigrated:

2x 5KVA EFC Lithium batteries

1 Lux Power SNA500 Inverter

 

Can I connect the above together to still push back to grid after batteries is charged? If so can you perhaps give guidelines how?

 

Thanks in advance

You could compare it to Microcare's solution for a grid-tie inverter with battery backup. Main idea being that the grid-tie inverter goes between the meter and the battery inverter, ie. the grid-tie inverter is on the input side of the Luxpower inverter. The difference is that with your Luxpower inverter you would have the option to add panels to the Luxpower's MPPT to increase your solar generation, but it could not export any of that power, just assist to charge batteries and run loads, but in doing so maybe free up the GTI to export more.

Whether there are any other specific reasons why this couldn't work for your components, either technical, or if there's a municipal regulation or whatever, someone else would have to give a 2nd opinion.

http://microcare.co.za/wp-content/uploads/2016/02/Microcare-Grid-Tied-Inverter-with-Battery-Backup-Solution-v2.0.pdf

http://microcare.co.za/wp-content/uploads/2016/02/Microcare-Grid-Tied-Inverter-with-Battery-Backup-Solution.pdf

You have many solutions to AC couple with the Grid tied machine. 

4 hours ago, Steve87 said:

You have many solutions to AC couple with the Grid tied machine. 

As a grid tied user it would be interesting to hear how to handle some options. Grid tied outside of using a Hybrid is not talked about a lot. 

I'll spare everyone the lesson as I'm not the author nor I am a master of AC coupling but the fundamentals are easy to fathom. So you need a Hybrid inverter to be the host...It must be a hybrid as a hybrid will be able to spool the energy down when required. You must have a Grid tied or what is called now these days a solar only inverter. 

You must have them paired as 1:1 or the Grid tied machine smaller than the Hybrid. So 5kW Multiplus & 5kW or less grid tie inverter with its array. 

The output of the Multiplus is connected to the Grid tie inverter. The Grid tied machine then sees "Grid Power" so to speak & will produce it's AC source of power to the same AC output to power loads accordingly to meet demand. 

Please this is just a very very watered down version. The Sunsynk has the exact same capabilities except it makes use of the Aux port. You can then use AC power from a Grid tied machine when the grid is down. In my opinion this is a very very sophisticated way to make use of cheaper grid tied machines that are already installed and or to add MPPTs. 

The Concept was proven between co-operation of Victron & Fronius however, this is not a dark magic trick it's actually just understanding the fundamentals correctly & applying them. 

 

The New Solis S6 Range Supports Ac Coupling with frequency Shifting could be a solution to your problem. 

Frequency shifting is very important because that will allow the host hybrid inverter to throttle the Grid tied inverter when there is no longer an energy requirement. 

Edited August 24, 20233 yr by Steve87

Yes however the main reason for frequency shifting is to prevent the battery bank from overcharging theoretically when the Grid tied inverter is coupled to the load side of the hybrid inverter and the hybrid inverter battery is not fully charged the frequency will be 50HZ which in turn will allow for the inversion process to go in reverse argument sake 230 VAC to 48v DC which in turn will charge the battery however when the battery is full the Grid tied inverter will change its frequency in increments until the frequency is at such a point that the inversion process is out of synchronization preventing the batteries from charging. Even when the grid tied inverter is running at a slightly elevated frequency normal loads will still be able to use the power generated by the grid tied inverter without using battery power.

1 hour ago, Powerforum Store said:

The New Solis S6 Range Supports Ac Coupling with frequency Shifting could be a solution to your problem. 

If one is adding a hybrid grid-tied inverter like a Solis or Sunsynk (3-phase in this case - 1x Omniksol-5k-3P-TL2), then one may as well chuck the old inverter out and let the hybrid do everything. Less complicated than having to AC couple, and fewer conversion losses.

Thanks guy for some very informative replies. Thus the clever hybrids solves the problem of frequency shifting that the more common inverters could not do unless you had some comms between hybrid and pure solar inverters.

The Solis without comms can now be used very well if I understand it correctly. 

 

1 hour ago, GreenFields said:

If one is adding a hybrid grid-tied inverter like a Solis or Sunsynk (3-phase in this case - 1x Omniksol-5k-3P-TL2), then one may as well chuck the old inverter out and let the hybrid do everything. Less complicated than having to AC couple, and fewer conversion losses.

I see those with Sunsynks that removed their Solis grid tied only inverters as a means of having more PV connected to what the Sunsynk on its own can handle. 

@smnic123

Let's try and explore the OP question. 

I would split off essential loads on the DB and connect to the Luxpower. 

Then run the SNE as a UPS and charge battery from the grid from the free power generated by the grid tied. 

In order to fully use the SNE add a few panels to the SNE so that one can charge battery and power essentials during longer outings when the grid tied is inactive. These panels can also be used to charge the battery during the day and cycle the battery during night time. 

May be a not such a clever solution but using equipment you have or a low spent to provide back up power. 

Edited August 24, 20233 yr by Scorp007

Just something else to consider when approaching Ac Coupling. I also advise care must be taken when using a high frequency hybrid inverter for AC coupling. A low freq hybrid inverter is more rugged for absorbing backfeed power surges from grid tie inverters. If you do use a HF hybrid inverter with AC coupling it should have a separate load dump capability to take momentary backfeed power surges from grid tie inverters. Another point to consider a Ac coupled system has 3 convertions making it less efficient that a hybrid inverter which has 1 convertion from dc-ac.

Edited August 24, 20233 yr by TaliaB

Here is an exact example of AC coupling via the Gen Port of a Deye 12kW 3 phase inverter. The pairing is a Kodak 4.6kW Grid tied machine but it's actually a Solis dressed up in Yellow. 

Must admit this pairing works beautifully together. 

One can see the 4.4kW coming from the Kodak that is AC coupled via the Grid port & crazy to admit this is a Single phase Kodak. Another very interesting topic is that there are 2 different model of FreedomWon Lithium batteries here. For all those people that still think that Inverter Comms is the holy grail of the solar game. 

But it works & works extremely well...

AC coupling is magic especially for those with a massive grid tie system.

Edited August 24, 20233 yr by Steve87