Solar float mode: Necessary?

Snowman9000 wrote:
As a practical matter, is float mode necessary with solar charging? As an alternative, the controller would simply stop charging when the battery was full. The next day the process would repeat.

Floating was developed to maintain batteries over weeks and months of continuous charging. Solar charging is not continuous, and the cycle restarts each (sunny) day.

I wonder if solar float mode is "because we can and the customer thinks they need it", rather than because it produces any real benefit.

Couldn't the extra watts put in at float voltage be instead put in at absorption voltage? Amps would be low; charge pulses would be short. Is there float in an automotive alternator charge?

Think I understand where you are coming from. When not using the batteries, I drop the solar controller's float down to 13.1 for the usual reasons. And like you suggest, I could probably turn it off completely without any ill effects as every morning the batteries would get full charged.

But when boondocking and using the batts during the day, I would rather have the batteries charged up as much as possible before nightfall. So I set float quite high at 13.6V or so. If battery V falls below (13.6-0.5) V, the solar controller moves into MPPT mode if there's sunlight.

13.6V float is much lower than the absorption voltage (14.8V), but as long as the controller can maintain it, I figure the batteries are in good enough shape for the evening.