I did a test with my new lithium batteries and my ecoworthy mppt controllers to see what happens. Both set to the same voltage (14.4 and 13.4) and one set slightly lower (14.3 and 13.3).
In the first case both controllers go flat out until one sees it has reached 14.4 and it drops into float - showing 0 float amps. A second later the other mppt sees 14.4 and drops into float - and shows 0 amps. Nothing happens then until the batteries drift down to 13.4 (takes ages) where the mppts start a tiny float current (way less than 1/2 amp in total)
In the second case it is all the same but one mppt drops out a lot sooner
The zero float shows the BMS is smart enough to shut off any charge when full and is not fighting the MPPT that have dropped into float. And the mppts do nothing until some load (eg lights) is switched on - then they ramp up float current to maintain 13.4 (eg if the lights need 5 amps the mppts provide 5 amps and the battery does nothing)
In the first case both controllers go flat out until one sees it has reached 14.4 and it drops into float - showing 0 float amps. A second later the other mppt sees 14.4 and drops into float - and shows 0 amps. Nothing happens then until the batteries drift down to 13.4 (takes ages) where the mppts start a tiny float current (way less than 1/2 amp in total)
In the second case it is all the same but one mppt drops out a lot sooner
The zero float shows the BMS is smart enough to shut off any charge when full and is not fighting the MPPT that have dropped into float. And the mppts do nothing until some load (eg lights) is switched on - then they ramp up float current to maintain 13.4 (eg if the lights need 5 amps the mppts provide 5 amps and the battery does nothing)