I envisioned an LED system with a healthy sized gel battery.... charging would take place when the system is disconnected. With the right battery you could probably run such a light string all summer and only need to charge it a few times. With a solar array, never.

Leaving a charger connected would defeat the purpose. And some chargers will only charge until the voltage level is met, and not restart unless disconnected anyway. A battery maintainer or tender would likely be smart enough to charge when the voltage drops. But it's a moot point.

One thing I can say with certainty here is that the 120V string of lights above the pool MUST GO!