I am setting up a mutiplus to charge my Renogy lithium batteries and I am not sure about what to do for the float voltage. According to Renogy my charge voltage is 14.4, cut off is 14.6 but it doesn't say if you should have a float voltage.
asked
Charging parameters for multiplus 3k and Renogy RNG-BATT-LFP-12-170
I think you should go back to Renogy and ask what there float voltage is I would think it would be around 13.6
Bulk/Absorption 14.2 to 14.4
Length of time for absorption 1 hr
Float 13.6
The above are mostly generic values so you need to find the correct ones from your battery suppler or take a guess
Renogy didn't really give me a good answer to the float voltage question, they said
"We are in the process of investigating whether float is indifferent or has an effect on our particular battery"
Renogy gives a cut-off current, so to stop charging after that. Lithium doesn't like to be trickle charged.
But..as most systems have loads attached to the batteries, you want a voltage to use to prevent discharge of the batteries. That's where the 'float' voltage comes in: configure it to the value the batteries aren't loaded, for LiFePO4 about 3,35V per cell = 13,4V
This can provide another problem: in an ESS system the system will actually discharge the battery to reach this float-voltage. As you didn't tell what kind of system you have, I don't know if this is an issue for you.
This is for an RV, so essentially a backup system with solar, an ESS with the intent to keep the batteries 100% charged until the shore power (grid power) goes away.
I have two concerns at this point, first is the Renogy battery doesn't have output contacts from the BMS so I do not know how to trigger the Multiplus to turn the charger off after the battery is fully charged if I don't want to use a float voltage such as when in storage and what triggers the charger to charge again if the battery does need "topped off". My second concern is If I am connected to shore power and using the RV 12v system for lighting, fans and so on how do I keep the battery from cycling unnecessarily (I assume this is when I want a float voltage). I assume I need to program the Multiplus for each situation but perhaps there is a profile that works in both cases?
I am sure it is something I have missed in the manual but for the life of me I re-read it and I have not figured it out so any help would be appreciated.
