Great to see such deep knowledge, some minor quibbles here.
Basically, every charge cycle "damages" the battery by the formation of dendrites. Think of it like "cumulative damage".
Ordinary wear and tear even under ideal coddling care conditions includes many incremental factors. Dendrites are drastic, signs of gross abuse, especially high C-rates. Of course that may be required by the needs of the use case, lower cycle life accepted as necessary.
> Every time you charge the battery, they accumulate damage
Every time you cycle, either / both charge & discharge usage patterns are at play.
And let's keep the term "damage" to mean "reduce longevity" as in departing from optimal coddling care conditions.
For example, a LFP pack lasting over 10000 cycles, or LTO 10x that, has not suffered damage as such, at all.
> The lower the final charge voltage is, the less damage is done.
This is only true down to 3.40V for LFP, and 4.05V for li-ion / LiPo. There is no detectable longevity increase by stopping charge before those points.
And assuming charging terminated before current trails to 0.01C, Floating **at any voltage** is likely reducing longevity.
See below for details
> And cycling between 30-70% is better than cycling between 60-100%.
Actually yes, sacrificing lots of capacity, and cycling around the midpoint is indeed optimal, but the cost is just not practical for private use cases much less consumer owners. Fine for NASA sending cells into space for decades long use cases though.
> The higher the rate of charge, the more damage is done. Same for discharge.
Yes, charging at 0.4C and discharging below 1C is very gentle, higher shortens lifespan. But very temperature dependent, this is at 77°F/25°C.
Pre-heating cells allows for much higher charge rates and much better discharge performance. Fast charging in Arctic ambients can instantly render a bank worth thousands into scrap.
> considering setting up a float charge. LiFE batteries do not NEED a float charge.
No, see above, Floating is for other chemistries, always damaging to LI.
Most of all, never leave any LI chemistry cells not currently being cycled at high SoC% for long periods of time.
If the charging / power source is used to feed loads, use a cheap lead batt as buffer and take the LI bank offline with contactors or manual switches.
Only charge the cells soon before loads need feeding, obviously within the constraints of practicality and the use case's needs.
> if I have shore power, I usually have it for a long time, and the slower charge rate is just better for the batteries
Generally true, but going **too low**, say under 0.05C risks overcharging, need to switch to CC only profiles, simple HVC, not holding CV / Absorb for long if at all.
And the voltage setpoint needs to be tweaked down, especially with LFP, say to 3.35V