FoxESS Community - Owners & Installers Forum

Hi All,
I have an AIO system with 7 HV2600 batteries attached, and all works well. I would however be happy to add a further 4 batteries were that possible. It seems that 7/8 is the maximum number that can be utilised with the AIO, but I see other members of the forum far exceed this - Will for example has 26 batteries. How is it possible to install the extra batteries please, and can it be done alongside the AIO or am I snookered?

Fox AIO unit with 7 HV2600 batteries
4.65Kw solar panels
Daikin 8Kw Heatpump
Eddy Solar Diverter
Hyundai Kona 64Kw EV with Ohme 7Kw Charger
Gas Meter - Returned to sender....

Will has 24 HV batteries, but he also has 3 inverters, and each inverter has 8 batteries.

The maximum number the AIO supports physically is 4, but you’ve obviously chained in some extra’s external to the cabinet - the AIO, H and AC1 are all the same in that they officially only support 7 HV batteries as the inverter max DC voltage is 450V.

There are a few users that have an 8th pack added, it’s not recommended as the inverter cannot reach the necessary voltage to charge all cells under all conditions - but if you keep your batteries in a reasonably warm environment it is possible, although FoxESS will say it invalidates the warranty - in your case they would say you’ve done that already by extending the AIO.

So all in all you are at the maximum battery storage, and the only expansion options would require more spend on additional inverters and associated BMS / batteries.

Hi Dave, many thanks for the reply. Very disappointed to hear that I may have invalidated my warranty, the AIO unit has dip switch settings for up to 8 batteries. Yes I have 3 stacked outside the unit but all professionally installed.
Unless I misunderstand you I can then have additional batteries as a separate block as long as they operate through a separate inverter and BMS (assume that is Battery Management System, I truly am out of my depth with all of this). I do have 2 solar arrays, 3Kw for which I get FIT payments and 1.65Kw as a separate array. Would I need to charge one set of batteries with one array and use the second array for the second stack? We fitted the first when we bought the bungalow 11 years ago, but have only got into batteries, ASHP and decarbonisation in the last 12 months.

Additional thought Dave,
Were I to remove the 3 additional batteries from the AIO then connect them with say 5 new ones in an 8 stack using an additional inverter and BMS would that be workable please?

Don't get me wrong, i'm not entirely sure what Fox would say about your additional batteries but the unit was not designed to be an all in on with external batteries attached - and I totally agree the unit is more than capable of supporting the 7 batteries.

The one thing I do know is they will definitely pull you up on having 8 batteries, 7 is the maximum the inverters charger can support under their warranty conditions.

The later inverters H1 (G2) and KH series all have a higher battery voltage capability and so 8 batteries is possible with them.

I think the short answer on expansion is that it can be done, but it will be a lot of complex work to do it, it will be expensive and it won't be elegant - I won't describe it in too much detail here but it would require your consumer unit to be split and a lot of extra wiring.

The better solution would be to replace your AIO with an H1 (G2) inverter which can take your existing 7 batteries (plus one more), you can then install another H1 (G2) inverter with another battery stack (again up to 8 batteries) as the G2's can be wired as master/slave - the 2 inverters work together sharing the solar generation and balancing the load.

William has done a video of his K series which shows this parallel mode in action https://www.youtube.com/watch?v=aot3Y5eSGGw

The beauty of this if you can afford it, you can keep adding inverters and battery storage to your system to scale it as big as you want.

Hi Dave,
thank you so much for this information, and for you taking the time to reply.
I'll get in touch with my installer, let him see the video and see if he can cost it out form me..

Your help is invaluable

best regards,
Ray

Hi Dave - sounds like the G2 gained the ability to do this Master / Slave config vs the original H1? If so that's very interesting, I hadn't realised that was the case.

calum wrote: ↑Tue Jun 11, 2024 9:51 am Hi Dave - sounds like the G2 gained the ability to do this Master / Slave config vs the original H1? If so that's very interesting, I hadn't realised that was the case.

@Calum, yes you can 'only' parallel up to 5 inverters - but a great expansion feature, and i'm also hearing that the EPS output is more of a pure sinusoidal waveform for those people who run off EPS and have sensitive electronic equipment.