You are assuming that the cells discharge exactly the same. Its been demonstrated many times over that when the cell voltages get to the knees, the weakest cell(s) rapidly change voltage.
In your case, an 8 cell pack with a nominal voltage of 24v and an inverter cutoff of 20v.
In the highly unlikely case of all 8 cells dropping to 2.5v this works fine.
In the real world scenario, what happens when the cell voltages are:
2.8, 2.8, 2.8, 2.8, 2.5, 2.5, 1.9, 1.9 (its 20v for the battery when the inverter cuts off)
You've destroyed 2 cells.
This is the primary reason that there is cell-level voltage monitoring and management (cutoff).
Your BMS should have thrown a LVC long before the inverter one kicks in…The build in LVC in inverter should be last resort when BMS failed twice and for that 20V shut off is ok. BMS first instance inverter gets shut off due to „big loads shut off“ event to prevent bank to go below 25 or 30% SOC, 2nd instance „emergency event all off“ LVC at 10% SOC.
Get a good BMS like Tao, REC or with some additional workarounds (optocoplers) Electrodacus and it does all what you need and shuts its off via the remote on/off Port whenever you must, need or want. Sure when the other gear is programmable like Victron you can add another layer of security but also this adds also another layer of complexity. Eg Electrodacus measures on cell level and execute all cut offs on cell level while the Victron or any other inverter LVC can just act on whole bank/voltage level, so who does the better job here? Without any doubt the BMS.
Then you can focus on what you really need, in this case a reliable 3kw inverter then can carry a big surge and a sungoldpower should be more then ok. The charger in the sungoldpower is not the best but a more then perfect backup in case my Victron smart Phönix charger dies….so I buy sungoldpower as inverter and add a Victron smart Phönix 50A charger to do the AC charger job all controlled by BMS on cell level. In case i need rapid AC battery charge I use both
and operate the backup manually by switching the AC in breaker on/off for the 230V AC in that protects the AC in cabling anyhow. Same with the inverter, for everyday loads a 3,5kw HF one running on 1,5kw max is on standby always, the big lump LF 4kw runs the electric galley and gets turned on in average Max 30min twice a day or the 230V tools like jig saw or in emergency the big 230V high volume pump. So Standby power of LF one I don’t really care. But if that fails the HF can still run 2 of 3 burners of the induction stove or the microwave.
And in case „of the all in ones“ like Victron Multiplus, yes that’s very comfortable BUT when it fails you don‘t have an inverter, charger and ATS.
For me for an „sailing around the world to remote places catamaran“ simplicity, redundancy and reliability is the key. So I prefer to have it modular 1+ backup inverter, 1 + backup charger and simple massively overrated transfer switch…as simple as possible and controlled by BMS. If BMS fails I can still operate all manually for some time and have a 2nd BMS (Electrodacus is 150 Euro) as spare to replace…backups depending on priority instant (2 Chartplotter+2 iPads act as one in parallel all the time), by flip of a switch (eg 2 autopilots installed parallel) or manual reconnection or physical replacement….in case of AC charger or inverter even physical replacement in a week is more then sufficient….all I need that’s critical is 12V direct from batteries eg autopilots, pumps, navigation equipment (possible 5v USB via powerbank and 12V),lights, watermaker, fridges, freezers, pumps….840AH LFPHouse, old 300AH FLA house/starter (now only starter engine STB) and oversized 180AH FLA starter (engine BB) gives triple backup here…
