The voltage of lifep04 cells means that batteries built from lithium lifep04 cells match lead acid perfectly
The float voltage of lead acid devices ie 13.6v means a cell voltage of 3.4v per cell which fits perfect
ie you can go out and buy any lifep04 battery and drop it in to any device that used a lead acid battery
edit: forgot one exception when it comes to 48v (though all talk about 48v batteries generically ie referring to 48v and 51.2v nominal batteries as 48v batteries)
batteries you have to make sure to buy a 16s battery ie 51.2v nominal voltage, some manufacturers make 15s batteries that is a 48v
while 4x 12.8v (though we talk generically 12v again) lead acids is 51.2 which the 16s matches perfectly
so in that inverter you would have to set voltages different if 15s like the pylontech /some shoto models
Irrespective if the lithium lifep04 listing states drop in replacement or not
The only caveat is with the lithium you have to make sure that the bms amps is able to supply your load
ie the rule of thumb tends to be to have a bms that can supply at 1c
a 100ah battery tends to have a bms that can meet 100a load
Thus the alarm size battery that is 7ah tends to have a 7a bms which is a problem for UPSs
You can however look for a high drain item that has a bms that can meet the load
That is the top side now the bottom
If the ups/inverter is designed to switch off at the 50% mark of a lead acid ie 12v ish
It is perfect as you would be very close to empty on a lithium so would not lose capacity
If the device switches of at 10v ie totally flat also not a problem as the bms will switch of the battery to protect the cells
Though spec sheets of lifep04 state they can be used down to 2.5v meaning the 10v shutdown would be a totally flat shutdown
Which a person should avoid for convenience
As dependant on inverter/ups
You may have to jump start the bms
ie if the bms switches off the battery it waits until it sees charge voltage
And some ups/inverters want to see battery present before they charge
Hence why you have to put some power on the battery for the bms to see the charge connect the cells and for the inverter to do the same
A manual shutdown before you hit this point removes this slept