In the Constant Current stage the charger or controller will supply as much current as the battery can accept. If the current is not constant it is not a constant current stage. Typically this is going to just be maximum power
Because solar output is highly variable on a second by second basis, the controller's output necessarily varies, the controller takes what it gets and passes it along. Smart chargers and controllers typically start charging with the CC stage to determine the SOC of the battery. They then stay in that stage until the internal resistance of a battery rises to a point where the voltage required to produce that constant maximum current reaches the Absortion voltage. When it reaches that voltage, it holds the voltage constant and drops the current to maintain that voltage. When the current reaches a set point, the charger/controller drops the voltage and the current to a float stage. The same happens with a smart regulator. Shore power chargers a a little different because the power supply is constant.
The internal resistance of all LA batteries decreases with a decrease in the batteries SOC. Victron Controllers are not concerned with the batteries voltage beyond the difference between the solar panel's output voltage and the battery voltage which must be at least 5 volts. The charge stage, CC or CV is not determined by the battery voltage, it is determined by the battery's internal resistance and its ability to accept the amperage being presented to it. Reduce its acceptance rate (due to increased internal resistance) and the voltage goes up and the current down, basic Ohm's Law.
There is of course a relationship between the battery's voltage, SOC, and internal resistance. The higher the SOC, the higher the voltage and the internal resistance. Some devices, like the Balmar SG200 do use voltage, along with some other information, as proxy for SOC, other regulators, like Wakespeed and Zeus, use a shunt to measure the amps going in and out to calculate SOC.
All of what I said can be demonstrated by using the same solar charging system on a LA battery bank and a LFP battery bank. When I had LA batteries there was clear evidence on the history display of the controller changes stages from CC to CV to Float. After changing to LFP batteries the controller rarely goes into any stage but CC, unless I am motoring a lot or on shore power. The reason this occurred is because LFP has a flat charge/discharge curve and can accept the full current output until somewhere above a 95% SOC where as with LA batteries the internal resistance begins to limit acceptance at around 80% SOC causing the controller to shift to the CV stage.
Yes, I made an error in the Ohm's Law formula, it is indeed E=I*R, I attribute the error to an oversight and a late night post. Regardless of the error, the important idea is the relationship between resistance, voltage, and amperage and how it effects battery charging and controller/charger behavior.
Snide remarks add little or nothing to anyone's understanding of a topic and only serve to undermine the speaker's credibility.
