connecting mppt/inverter to bms/lipo3.2v batt

My first question is EXACTLY (links?) BMS do you have? There are many variations--But what I am questioning at the moment is does this BMS have FETS (transistors/switches) at the battery negative (or other) terminals?

When you say 250 Amp balancer, it sounds like the BMS system can measure battery bus current and should have the ability to "turn off" the battery bank if cell voltage(s) are out of range (more or more cells too high/too low of voltage) or if there is too high of current through the battery bank/string. This (these) switch(es) are (more or less) the last "fail safe" for the battery bank (prevent cell damage, over heating, etc.).

Once you figure out the BMS/Battery bank wiring/... Then it should be the typical connect the + battery to your + bus bar... And the negative battery terminal to the (nice to have) large current shunt/precision resistor (to measure current into/out of the battery bank (usually connected to a Battery Monitor to estimate current/time (i.e., amps*time = Amp*Hours in/out of battery). You may not need/have the precision resistor if your BMS does the State of Charge/battery current monitoring/reporting for you.

https://www.solar-electric.com/catalogsearch/result/?q=shunt (various shunt types)
https://www.solar-electric.com/victron-energy-bmv-712-smart-battery-monitor.html (example of a standalone battery monitor--Very nice one)
https://www.amazon.com/battery-monitor/s?k=battery+monitor (examples of less expensive standalone battery monitors--Read Specs carefully--Not all have the "same functions").

Once you have the "48 volt Bus"--Then the MPPT charge controller, inverter, etc. are connected as usual...

For safety, each + terminal to bus bar should have a fuse/circuit breaker rated for maximum wiring current to prevent a short circuit starting a wiring fire. And, ideally, the + battery to bus bar should have a 250-300 Amp fuse/breaker/cabling too.

Review the manuals for your Charge Controller, Inverter, etc.... There are lots of variations and configurations (from inverter only to inverter-charger to inverter-charger-solar charger-generator controller, etc.)... 

Details matter here (both for function, and safety).

-Bill

This from the Daly website:

https://www.dalybms.com/8s-bms-wiring-tutorial/

Does this help?

Note the single line connections at upper right to Motor/loads/Charger are actually + and - heavy wiring (and possibly a pair of bus bars for all the "T" connections.

-Bill