Using 12V 260ah AGM batteries with on-grid system

[Jonathan3000]

Hello fellow solar enthusiasts! I'm working on a system for my house that would use solar and the grid to charge 4x260Ah 12V AGM batteries so that I could use the battery power during peak hours when the electricity prices are the highest. I currently have a Fronius Symo hybrid inverter, but I'm learning that it might be difficult to use it with any batteries.

I have been looking into getting a separate battery charger/inverter or maybe changing the Fronius Symo to a Fronius GEN24 or maybe a Growatt battery ready inverter. Can you help me out on what would be the best path forward? I'm planning on making my own software and using a raspberry pi to handle the logic when to charge the batteries from the grid and when to use the stored power.

Victron battery charger/inverters might be an option also, but getting three-phase current would maybe require three separate units which would be very costly.

 

[SamDeleted]

Hi Jonathan, not sure if I can help much

Being in Finland and needed 3 phase you're not going to be spoilt for choice , there will only be a few options


Have you found a growatt of suitable spec ?

 

[hwy17]

AGM round trip efficiency could be as low as 80% which might eat a lot of the benefit. But maybe you have one of those extremely low overnight rates.

 

[Jonathan3000]

All the Growatt systems I have seen either require some sort of ARK-XH high-voltage batteries or are for off-grid systems only. So, no luck there yet. This Victron documentation gives me hope it might be doable though...

 

[Jonathan3000]

The rates vary here on an hourly basis based on the Nordpool prices, there is plenty of room for savings during each 24h cycle.

 

[hwy17]

The rates vary here on an hourly basis based on the Nordpool prices, there is plenty of room for savings during each 24h cycle.

Do you get actual market rate passthrough? That's cool.

Does it pass through negative rates? I imagine with delivery charge it would still come out positive of course.

 

[Jonathan3000]

Today was actually the first day in history that the pool had a negative daily average rate. You're correct, overall positive day using solar, but it did cost money to feed electricity into the grid.

 

[Jonathan3000]

Seems to me that the Victron Multiplus-II might be a good way to proceed. I'm currently unsure if I would need 3 Multiplus devices to get 3-phase electricity out of the batteries...?