question

I forgot to mention that the batteries are 10kWh each (5 in parallel), and each has a PACE BMS installed.

You're going to reasonable expense. Pick something off the certified battery list.

It's so much less hassle. With a 3rd party BMS you and the battery co are responsible for support.

He who goes off piste, often gets piste off. :)

https://www.victronenergy.com/live/battery_compatibility:start

Sounds like a nice setup but I agree with using batteries on the list. There are other great options but being on th elist means it's tried and tested and you'll have support.

AC coupled Fronius inverters work well with the Victrons. I suggest you make a network connection between the Cerbo GX and the Fronius inverters, ideally by cable, so as to take advantage of the modbus communication in both devices. You'll have to activate/turn on this in both. Also set up you Fronius meter as a secondary meter or disable it altogether when you get the Victrons in, otherwise you'll have erroneous readings.

If you do decide to add extra panels to the shed roof, I suggest you use a Victron MPPT connected to your DC Bus or Lynx Distributor. That way, in case of a total power outage and you totally drain your batteries, the MPPT(s) will charged the batteries enough to allow the Multi's or Quattros to wake up, start the Fronius and regain normal power access and charging ability. As you know, the Fronius turn off in case of aa power outage - this won't happen if correctly installed AC Coupling in an ESS setup.

I'd love to have my company help with the install but we're on the other side of the globe. Good luck!

Thanks for your replies. I had not realised there was a supported/compatible battery list and will have a look and see what is available.

A bit of background. I use (lead acid) battery powered wheelchairs and lithium battery powered ventilators, so have some autonomy when the power goes down. I can survive, but with everything you can imagine in the house on standby for remote control use, power cuts are a pain. I can't even open my front door when the UPS gives up after a few hours!

I bought 16 x 80Ah LiFePO4 cells in the past to replace the MK Gel lead acid batteries in my wheelchair. After the last power outage I installed them in the shed instead. They are configured 8s2p, hooked up to a reasonable BMS and connected to a Smart Solar 100/20 and a few panels.

A Phoenix 24/500 powers my rollerdoors (so I can at least get in the shed) and charge my ventilators in emergencies.

An Orion-Tr Smart 24/24-12 assures I can recharge my wheelchairs if needed.

Currently I only cycle about 400Wh a day, so there is plenty of reserve power for emergencies.

Some time in the future, the 16 x 80Ah cells will have go into the wheelchair to replace the lead acid, and I am ordering 16 x 280Ah LF280K (+ a larger BMS) to replace them. Prices are relatively low and installation is simple and straightforward.

I would also like to make my fridges and freezers continue to work during a power outage, and can of course duplicate the setup I use in the shed. Rather than doing that, I was thinking of the setup described above. It will allow me to recharge my batteries from the existing Fronius solar system and reduce power costs through increased self consumption. I will also be able to power everything I currently do, with or without the grid. A quick analysis of 4 years of Fronius data showed that with a 50kWh battery I can even continue normal consumption during the occasional extended period when there is little sun.

The cost of the Quattros is high, but I know they will do what is needed, are certified for use, etc. The only problem I have is that the cost of home batteries are a multiple of the cost of the sum of the parts!

With prices for an LF280K (6000 cycles) hovering around US$100, the cost of 50kWh of storage (a bit larger actually, using 64 cells) is under US$7000. Add to that the cost of cabinetry, BMS, import, transport, etc. and you are at a fraction of the price complete batteries are sold for locally.

I am fine taking the risk that the cells I buy are actually the cells I think I am buying. The BMS, the part that has to perform flawlessly with the Quattros, is where I have no idea. I agree that rather than trying to invent the wheel, I should go with a known to be compatible battery, but those costs would be too high. A way around this dilemma, is if there is a supported/compatible BMS that I can use.

Another option may be to use LF280K cells to make lead-drop-in-replacement batteries with an inbuilt BMS, like SimpliPhi. At this stage I cannot oversee what the drawback of such a system would be where there is no communication between the Quattros and the BMS.

PS Whatever battery I buy, my existing Smart Solar 100/20 and panels could be used to recharge empty batteries so the Quatros can start. A great tip!