How can I expand my battery storage?

[Tarleton lad]

Hello, Still trying to source a good used Solax Gen2, 6.3kwh Triple power battery to add to our existing 12.6kwh system but no luck as yet. Just wondering if there is a way to add another battery, ie if it was a different size/model or even a different brand? I think I heard that it might work if instead of linking to existing batteries a separate connection was made to the inverter or maybe it was a separate inverter, not sure. Our existing inverter is a Solax X1 AC 3.0

 

[johnb2713]

You can make an AC coupled battery with it's own inverter charger at very competitive prices.

 

[Tarleton lad]

Thanks John, How would that work alongside my existing 2 x Solax 6.3kwh batteries? Would an extra inverter cause issues with our DNO? Would a new Solax 5.8kwh be OK and there does appear to be plenty of used inverters available. How would the 2 separate battery system feed into the house load? I would be using a local sparky but want to do the research to ascertain was is possible and safe before contacting him as he is fairly new to battery storage.

 

[johnb2713]

Thanks John, How would that work alongside my existing 2 x Solax 6.3kwh batteries? Would an extra inverter cause issues with our DNO? Would a new Solax 5.8kwh be OK and there does appear to be plenty of used inverters available. How would the 2 separate battery system feed into the house load? I would be using a local sparky but want to do the research to ascertain was is possible and safe before contacting him as he is fairly new to battery storage.

I have no knowledge of Solax inverters and batteries. An AC coupled battery is totally divorced from your existing solar/inverter/battery setup and effectively is just plugged in to the mains (it's wired into a consumer unit via a suitable MCB). The inverter has a CT clamp on the meter tails just like your existing one. The inverter can be set to charge during off peak supply and it will charge when surplus PV is available. When it sees import from the grid either because your existing inverter doesn't have enough capacity or if the batteries are depleted it will ramp up it's output to feed the load. I have just installed such a system using a Victron Multiplus II inverter and it works with no issues with the existing Growatt inverter. These things have to be able to work co-operatively, if they didnt, a neighbour with a storage system would conflict with your system.

 

[Geoff1946]

Please forgive if this is a stupid question and I've forgotten some basic principle, but what sort of current transformer can tell whether the current is flowing in or out ?

 

[johnb2713]

Please forgive if this is a stupid question and I've forgotten some basic principle, but what sort of current transformer can tell whether the current is flowing in or out ?

None of them.

Information from the CT compared to the AC voltage will give energy flow information including direction.

 

[Geoff1946]

None of them.

Information from the CT compared to the AC voltage will give energy flow information including direction.

Thank you. That I can understand.

 

[Tarleton lad]

Thank you John, very interesting. If I add another 3 kwh ac inverter to my existing 3kwh Solax inverter will I need to seek approval from DNO?

 

[johnb2713]

Thank you John, very interesting. If I add another 3 kwh ac inverter to my existing 3kwh Solax inverter will I need to seek approval from DNO?

I'm no expert in this field of rules and regs, my gut feeling is yes. Personally, I would set export to zero and use all of the stored energy myself, I don't see any justification fair the DNO to refuse permission.

 

[Oldman22]

I would say that if you do as John says and have zero export from the new inverter how are they ever going to know. You are already exporting from the original system so they are aware that you from their records.

 

[Tarleton lad]

This is starting to look like a possible solution. Does that mean if I fitted, lets say, a 5.8kwh battery and a 5kw inverter and blocking export that the new inverter would allow the batteries to discharge into the house load at 5kwh?? At the moment we can only draw max of 3kwh from the batteries via the existing inverter. 5kwh would be very useful, especially when charging our EV.

 

[binky]

I would say that if you do as John says and have zero export from the new inverter how are they ever going to know. You are already exporting from the original system so they are aware that you from their records.

Whilst that is correct, there's still a legal obligation to notify the DNO.

 

[johnb2713]

This is starting to look like a possible solution. Does that mean if I fitted, lets say, a 5.8kwh battery and a 5kw inverter and blocking export that the new inverter would allow the batteries to discharge into the house load at 5kwh?? At the moment we can only draw max of 3kwh from the batteries via the existing inverter. 5kwh would be very useful, especially when charging our EV.

Correct, exactly what happens here with my two systems.

 

[Tarleton lad]

I have a spare 20 amp RCBO, would that be OK for a 5kwh inverter? Do all inverters have the "zero export" function? Should I be looking for an AC or Hybrid model?