Forget about batteries. Lead acid are not usable (only 30-50% capacity can be used for better lifetime, so price per kWh is at least doubled), Lithium batteries have much better cycle life, but they are higher cost. Typical costs for stored 1kWh are about $1USD, etither Pb or Li.
I can suggest you much better and easy solution for your miners to save a lot on efficiency. It need direct connection to your solar array which should have maximum power point between 100 and 400V and already connected MPPT inverter (you have it already).
Solution:
1) If your MPP string voltage is around 400V, you can connect DC voltage directly to PSU DC input line just after PFC. You will have direct path from solar DC to miner PSU and you will eliminate some very small loses of PSU's PFC circuit. If RMS input voltage is higher than PFC set voltage (usually 380-400VDC), PFC controller just switch itself off and let voltage pass through. We have DC line, so RMS=DC voltage, so if you do not care about 3x 0.7V voltage drop across forward diode, you can connect DC line directly to AC main input.
2) If your MPP voltage is less than 350V, you sould connect DC line directly to AC input or inside just after diode bridge (2x 0.7V drop).
3) set your 12V output very little higher than your AC line PSU, so if your AC line PSU has 12.0V, your DC line PSU should be about 12.2 or higher.
You will feed your miners primary from direct DC-DC path, if DC line PSU has not enough power, it will switch itself off and your miners will be fed by your AC line. Your MPPT controller always keeps your solar grid at maximum power point, so you do not care what is your voltage within 300-400V range. In case of 100-400V range, your PFC can go less than 60V, so it will not switch off immediatelly when cloud comes on the sky.
This is general description. Some PSU's like Fortron Raiders, IBM 2980 or Bitmain's needs higher voltage to work and start-up, so your solar grid DC voltage range will be narrowed to 230-400V DC. Maximum DC voltage accepted by PSU is limited by input DC capacitor voltage (the bigges one in PSU).
You need to answer yourselves some questions here.
1) buying batteries: does it have ROI, when every kWh stored is about $1USD and needs additional charge controllers? Can your miners survive voltage variance between discharged and charged battery (11.5-14.5V) or need another DC-DC controller?
2) is it enough to save 5-10% efficiency to buy another high power PSU (MPPT AC inverters are not 97%, they are less depending on actual MPP votage set)?
3)
there is NO SOLUTION to connect PV panels directly to miners without power losses. The best way is to use MPPT controlles for 12V or any MPPT combination as shown above. You will always lose some power at conversion.
Buying cheap panels and cheap inverters may do better ROI than thinking about batteries and direct connections... There are 1200W on-grid outdoor micro inverters at $280, so if you have $0.55/W panels, it is $940USD per 1200W complete on grid system with super easy installation and unlimited stackability.
