My trailer had a major upgrade done by "Lewster", an experienced tech who is active on these forums. He added an inverter/charger and a solar system. Both systems have a display that shows system voltage and charging current. Both systems are configurable as to what the voltage should be for bulk, absorb/acceptance, and float charging.
The way it is set up, the target voltages on the solar system are 0.1 volts higher than on the on the inverter/charger (the specs for my batteries allow a range of 0.2 volts so both systems have valid settings). This means when we have sun, the solar usually provides enough voltage that the other system says "full charge, nothing to do". But if we are drawing a lot of power, the i/c kicks in.
At night when the sun fades away, the i/c kicks in.
This mostly works well. But on our last trip out, we did notice one time when the batteries needed some charge, and the solar was doing its best in a shady camping site. However, the solar was basically just keeping up with the trailer's loads but not completing the charge of the batteries. The inverter/charger saw high enough voltage that it did not pick up the slack. Even after dark, the i/c charger stayed in float mode. (I think we went to bed at -9 amp-hours from full. The next morning, we were at full charge.)