I have a standard drop-in 3x100Amps LFP bank. During the week and some weekends the boat is docked and plugged into shore power. There’s also a solar panel of 114W nominal (MPPT) on deck. Use a Cerbo to monitor, constant VRM connection. I can see the MPPT going through a full cycle of bulk-absorption-float every day even if the shore power charger maintains long term float.
Whats the problem?
From my experience with electric cars (EVs), I know that allowing Lithium batteries to sit for longer periods at very high (or very low) SOC is quite detrimental to cycle life. I understand that LiFePo4 may be more robust but still think the default charging to 100% seems less than optimal. (Have set the absorption duration from MPPT at 5min to minimize that at least.) At the same time, I certainly do want maximum SOC when cruising.
Idea:
A separately configurable “storage mode” for LFP batteries - as opposed to the normal “active mode”. This could work like this: A storage voltage or SOC (I.e. 50-70%) is set. This requires the charger/inverter to override the MPPT so that no unit will exceede the storage level. A timer/date and target SOC for active mode can be set so that the inverter/charger will charge to that level based on the timer. (Every n’th charging could be to 100% with 2 hrs. absorption to allow for cell balancing.) Normal minimum temps (>5°) secures long term winter storage.
I really don’t know if I’m trying to solve a non-problem here - but as more users become familiar with EVs I suspect these concerns will become more commonplace - so it would be great to either clarify this - or to implement a solution.
