Updating on the PIP4048 inverter charger. There is a shortcoming regarding the charge profiles and tricking it to do what I want for lithium cells.
I tried to explain this last night at our EV gathering the but didn't do a very good job at 11:00pm
In the charger settings of the pip4048. Under the battery type when you select custom or as they call it (user) battery setting for the charging profile. Your are only given two parameters to set (Bulk voltage) and (float voltage).
So when charging a lithium battery it's going to want to do a (absorb stage) once the battery reaches the bulk voltage you have set. You don't have a separate absorb setting to configure.
so I see no easy way to fool the charger into dropping to float Voltage once the set bulk voltage is reached. Without it first wanting going through it's automatic time based absorb stage first. Not what I want for lithium.
In my simple (charge once and use) application I would be happy for it to just reach a set voltage and just stop charging. In a offgrid application you would want it to drop to your float so the PV charger would cover ongoing DC loads throughout the day maintaining float V.
Typically you can trick most programmable lead acid chargers into doing what you want for lithium cells by letting it first give the battery all it can muster in bulk charging until the absorb CV-voltage is reached. Say in a 48v system charging to 56.8v (3.55v cell) and then have it drop to float V and just effectively skip the absorb stage.
You can do this by setting the (absorb voltage) at the same voltage as your (float voltage) say 54.6v (3.41v cell) Absorb V. Then float V at 54.6v as well. So basically it become a two stage charger. Bulk charge to a set voltage point then absorb & float are just the same voltage so it essentially just drops to float after bulk.
Unfortunately this PIP4048 unit is always going to want to do a variable time based absorb charge at the same voltage as you have set the (bulk voltage) at before dropping to float. There is no simple way of tricking it to drop to float after it's bulk voltage is satisfied. As you can not set a separate bulk, and absorb voltage they are the same setting
I hope I didn't confuse anyone with that.