Absorption Time Lifep04 battery's

[Collin Oulton]

Absorption time? I have two Renogy 48-volt smart lithium iron phosphate batteries in parallel I used them for about a year without charging to 100% not realizing that they needed to be balanced or how to balance them I currently set my Bulk to charge 100% and my absorption time 2 hours to help balance them I'm just not sure how long or how much time it would be okay for the batteries to be on Absorption

 

[sunshine_eggo]

Depends on your charge voltage.

My rules:

3.55-3.65V/cell for fast charge - 30-60 minutes fixed absorption time (dictated primarily by balancing needs)
3.45V/cell for slow charge (this is the one that maximizes cycle life) - 2-4 hour fixed absorption time (dictated by time needed to get to 100%).
3.375V/cell float

You likely need to hold them at 3.45-3.55V/cell for 24 hours to give them time to balance if they truly need it.

If you can monitor your voltage and current, imbalance/BMS protection is indicated by a near instantaneous jump to absorption voltage and a drop to 0A. If you observe a steady (and fast at the end) rise to absorption voltage following by a tapering of current to 0, you're likely balanced.