Backup solar battery system considerations.

[hsync33]

I (along with many others) have insulation sheets between prismatic cells to avoid shorts if the thin blue plastic outer layer gets damaged.


Manufacturer recommendation (at least for my EVE cells) is support to limit expansion at full charge - there are many threads on that on here. IIRC it protects the internal bits from separating to improve longevity.

I've seen the insulation sheets, pretty standard. I wasn't aware they recommended limiting thermal expantion. Always learning
It isn't done on all batteries, so I'm wondering if they are built differently? Coud be the case for EV manufacturers typical usage of various parallel cells instead of a single large one

 

[DIYrich]

I apreciate the advice and it's sound, but I already defined the scope of the system on the first posts.
UPS as main aim, summer grid injection (small ammount for self consumption) as secondary, whenever there is spare capacity available.

You really did not define your storage needs - kWh. For 7 kW of panels, that implies a daily usage of about 20kWh. Build a DIY battery using 280ah or 305ah prism cells from EVE or CATL, and a JK or JBD bms. Get the cells from a reliable supplier. Add a box if you can afford it. 100ah cells are fine too, but if you are doing all the work, might as well go the 280+ route.