As I've stated before, IMO, the Powerwall's high voltage greatly limits its versatility. It requires long strings of PV, and upgrading PV output essentially requires another full string of nearly identical panels, as I understand it. I'm free to mix and match my PV as long as I keep my strings below 150 volts Vmp. That's the advantage of keeping charge control separate from DC to AC inversion. Cost a bit more? Yep. Much more versatile and resilient? Absolutely. Only when Tesla markets a Powerwall in the 100 volt range will I even consider such. And I skipped the part where high voltage DC is a very squirrelly thing. A system like mine, with a good hybrid inverter, can be grid-interactive, buying and selling as I choose via fairly simple programming.
Edit: I see the Powerwall2 is available in lower voltages. Hopefully Baha will set me straight. What is the DIY cost of a 13.5 kWh unit these days?
Meanwhile I'm having fun salvaging used 18650 Li-Ion battery cells to upgrade my portable power unit which can supply anything from USB power up to 24 V and 150 watts of AC. Primarily meant to charge USB devices and charge/run 12 volt gizmos. It's a bit astounding how many lithium cells get discarded when they are perfectly fine. If the battery management system in these devices detects just one cell that is questionable, it'll render the entire battery pack inoperable (won't let it charge). Sucks to know those expensive 18 volt power tool battery packs you bought are perfectly fine if one knows how to revive them.
I disassemble the battery packs (mainly from laptops and power tools), test the cells for internal resistance and capacity, and match them into strings for higher voltage to arranged into power banks. My power bank can be charged with PV or AC power. Battery system management systems (for safety and balancing cells) can be had from Ebay ridiculously cheap these days since virtually every lithium-powered device has one. For $5 I got a little unit that can manage, balance, and display data on up to 7 strings of cells. I built my system so that individual cells can be replaced easily, and HD and Lowes provide a constant supply of high quality cells if one wants to dig through the recycle bin. Cells that don't test up to their specs get returned to the bin. Reduce/Reuse/Recycle can be such fun. Eventually I may build my own lithium powerwall.