Sure.
I think it’s first important to recognize a few things:
1) a connected battery will face some level of parasitic load, including from internal self-discharge.
2) A battery’s state of charge can be correlated to its voltage, which is the sum of the electrochemical potentials of the half cells (anode and cathode). These vary slightly based upon the alloys, pastes and other active chemical components in the battery, as well as temperature.
#1 is important because it means that batteries are always self discharging. Lead acid batteries (including flooded and VRLA/AGM) need to stay at exactly 100% for max life. A tiny bit more, and degrading corrosion occurs. A tiny bit low and sulfation occurs. #2 is important to realize that since the industry and end users lack configuration control, Thus the absolute truth on the absolutely correct voltage at temperature to define as 100% is variable. Thus everything else must be assumed to have a bit of error.
Float (or trickle, which is sometimes used interchangeably), is the elevated voltage level that provides an “equilibrium”. That is, where after a proper charging profile to 14.4/14.7V, the voltage is reduced to a level where any parasitics (self discharge) is offset at effectively a net zero level. Because there are electrochemical “activation” losses in charging, it takes a little bit of a voltage boost to squeeze the electrons in.
So float is a “lossless” interface (calling it an interface vs a voltage because it needs to be applied, it doesn’t naturally happen to be that high), or at least in theory. If the float voltage was kept exactly right for the battery chemistry and temperature, the battery would stay at 100%. Practically speaking, a battery connected to anything are a parasitic, regardless of light loads. The battery itself is a parasitic, see #1. Thus to have true and ideally maximum capacity and capability from a battery, you want it sitting at float.
There are two schools of thought though:
a) Float is never exact for any number of reasons, thus permanent “float” will result in some periods of corrosion and some periods of sulfation. This is because of #2 above. Thus prolonged float is causing some unforeseen damage, regardless of how small. You’re better off “fully” charging (which again is not an exact matter), and just topping up in a controlled way at some predefined voltage.
b) Since batteries are expected to provide max performance, float should be maintained, and a flag should be set if/when sustained current requirement goes too high. Any chance of damage or degradation is no worse than sitting at less than 100%.
I think I’d argue that if you have a true mission critical application, like a major backup power system or something like that, and max capability is required, permanent float charging is important. For vehicles, it’s such an inexact science, and battery replacement is favored to gain reliability, then getting in the ballpark to help gain longevity and offset losses is the best you can ask for. Thus why the NOCO/ctek approach is growing on me. Elevated voltages increase stress on electric components (like electrolytic capacitors on circuit boards). If after a prescribed duration on float, it shuts off and monitors, it should be good enough for a 3-10 year replacemebt cycle on the battery, and be easier on other electronic components, even if just marginally.
Let me know if you have questions.
