Solax Inverter not compatible with Fogstar Batteries, workaround or replace?

[OddLion]

First thanks to everyone on this forum. I'm a newbie here (please forgive any glaring mistakes) and have learned a lot from all the discussions.

I'm in the middle of a home solar installation - 19 Eurener 400W panels, Solax X1 G4 7.5kW hybrid inverter, Zappi, Eddi, and a 15kWh Fogstar battery array (batteries still not installed).

Fogstar was slow delivering the batteries, and in the meantime I double-checked compatibility only to find that the 51V batteries are apparently not compatible with the Solax inverter, which demands >60V input.

Obviously the installers should have seen this, and they claim they were told by both Solax and Fogstar that it would work. Hard to know, but it seems like human error.

They raised the option of installing an AC coupled inverter for the batteries, at their expense of course, but I fear this will introduce inefficiencies both in AC-DC-AC conversion (some energy is lost each time) and in monitoring and controlling the two inverters (we intend to get Octopus Agile), and also be another big box taking up space on the wall.

The other option is to reject the Fogstars and put in a bit of extra money to get Solax batteries. More expensive, but they seem good and will definitely play nicely with the inverter.

So, a couple questions if anyone has a minute:
1) Is the energy loss from the AC Coupled inverter workaround significant?
2) Will it be difficult to monitor and coordinate the energy flows to/from inverters, panels, EV, grid?
3) Are there advantages to having two inverters, such as if we get a power-hungry heat pump in the near future?

Any advice would be most appreciated, as we want to get this right the first (or second) time.

Thanks!

 

[binky]

I've used Pylontech 48v batteries with a Solax X1 before. That was a few years ago, and spec may have changed since then

 

[OddLion]

I guess the question is whether these DC voltage numbers are requirements or just suggested.

 

[binky]

spec is the same as the one I fitted years ago in 2019, data sheet below. The inverter needs to be set for the battery connected, I don't know if that changes voltage ranges, but most can cope with old battery tech like lead acid if set correctly.

 

[michael8554]

I thought these "High Voltage" inverters required the 51V batteries to be connected in Series, to give multiples of 51V to match the Inverters 80-480V input spec ?

 

[OddLion]

I thought these "High Voltage" inverters required the 51V batteries to be connected in Series, to give multiples of 51V to match the Inverters 80-480V input spec ?

Yes, that's what I thought too, until I read the Fogstar instructions that specifically say you cannot wire in series only parallel.

Has anyone wired them in series, and if so how did it work out?

 

[johnb2713]

Yes, that's what I thought too, until I read the Fogstar instructions that specifically say you cannot wire in series only parallel.

Has anyone wired them in series, and if so how did it work out?

You will run into trouble with the BMS. The batteries themselves can be series'd no problem, you would need to find a 32 cell BMS unit.

 

[binky]

I would contact Solax with the battery spec and ask if it will work together.

 

[johnb2713]

I thought these "High Voltage" inverters required the 51V batteries to be connected in Series, to give multiples of 51V to match the Inverters 80-480V input spec ?

They do but some batteries have issues with the BMS units installed.

 

[bladerunnerpv]

Have you contacted Fogstar about this to see what they think ?

 

[OddLion]

Have you contacted Fogstar about this to see what they think ?

Yes, they said "sorry, they're not compatible", which seemed pretty conclusive.

I'm still curious about the AC coupled inverter route, but if that is too cumbersome we may have no choice but to get different batteries

 

[bladerunnerpv]

Solax X1 G4 7.5kW hybrid inverter

spec says Euro efficiency for this is 97%
spec says battery charge efficiency 97%, and battery discharge efficiency 97% ?
it can output 7500W AC

Is the installer proposing leaving the X1 G4 in place, so using the hybrid inverter as a PV inverter only?

Guessing they would be looking at a solax AC coupled inverter
https://midsummerwholesale.co.uk/pdfs/x1-ac-1.pdfno euro efficiency quoted
spec says max battery charge efficiency 96.5%, and max battery discharge efficiency 96.5% ?
it can output 3680W AC
I'm not aware of a bigger AC coupled solax inverter, but not searched very hard tbh!

seems to me the usable power is better for the DC coupled hybrid in this case, and it sounds like you were going DC coupled in the first place anyway?

you could add an AC coupled inverter & battery at a later date if so desired?

others on the forum know this stuff better than me but hope this helps

 

[OddLion]

spec says Euro efficiency for this is 97%
spec says battery charge efficiency 97%, and battery discharge efficiency 97% ?
it can output 7500W AC

Is the installer proposing leaving the X1 G4 in place, so using the hybrid inverter as a PV inverter only?

Guessing they would be looking at a solax AC coupled inverter
https://midsummerwholesale.co.uk/pdfs/x1-ac-1.pdfno euro efficiency quoted
spec says max battery charge efficiency 96.5%, and max battery discharge efficiency 96.5% ?
it can output 3680W AC
I'm not aware of a bigger AC coupled solax inverter, but not searched very hard tbh!

seems to me the usable power is better for the DC coupled hybrid in this case, and it sounds like you were going DC coupled in the first place anyway?

you could add an AC coupled inverter & battery at a later date if so desired?

others on the forum know this stuff better than me but hope this helps

Indeed, this was a possible plan, but we've settled on getting Solax batteries instead. I know others (John comes to mind) have successfully coaxed two inverters to play together nicely, but I really didn't want to go down that route in a new system.

 

[bladerunnerpv]

No worries, guess you need to decide between tp58 and tp30 options then...