We do have some lead acid expertise on the forum - perhaps one of them will answer. Meanwhile, I'm not a lead acid person but in general.....
X20 lead acid batteries in 4 strings of 5 batteries model 12v170fs enersys powersafe batteries that have a capacity of 40kwh and DOD 20kwh.
Thank you
To confirm, you're talking about 20 of these -
https://alpinepowersystems.com/tele.../enersys-powersafe-v-front-terminal-12v170fs/ - at 170ah each. Arranged in 5 parallel groups of 4 in series for 48v nominal.
Do you know of a lead acid battery BMS suitable for a solar panel installation that has a solis hybrid inverter and
I would query both Solis and Enersys for info / recommendation as a starting place. For the $ they should be willing to respond 
The Solis Hybrid web page -
https://www.ginlong.com/us/Energy-Storage-Solutions.html#page3 - says compatible with a wide range of batteries. The key question is will it operate without communicating with a DIY battery bank. If not, then you need to change battery banks or inverters.
Assuming it can, then to discuss you're battery bank.....
Note: The primary purpose of a lithium-ion BMS is to protect against over charge/discharge, over/under temp and may include balancing. The over charge/discharge over/under temp doesn't seem to apply to the lead acid world - so you won't find "BMS"s for lead acid as a common item.
However, when you put 4 in series for 48v then I see these 4 way 12v 'balancing' units -
https://www.amazon.com/iSunergy-Battery-Equalizer-48V-Balancer/dp/B0BDF68PRJ/ref=sr_1_2 which make sense. You'd need 5 of these - 1 for each 4 in series groups. I don't have any 'brand' recommendation - I offer the link above as a discussion example.
