If you are in the tropics,
charging your wet cell batteries above 13.2-13.3V will cause them to develop gas bubbles and eventually dry out. We set our
solar panels to charge no more than 13.2V and have always returned to wet batteries. If your
solar controller allows this voltage adjustment, use that. If your solar controller only allows higher voltages, consider blocking some of the cells on the panel so that the maximum voltage the panel can produce is 13.2V.
If you leave the boat plugged in and on a battery charger, move the charger sense wire to the
AGM starter battery. This will cause the charger to just control battery
charging for the AGM which can be stored at float (say 13.6-7V) and would not be hurt by periodic full voltage charging. Full charging would occur after
power outages or if the boat is momentarily unplugged. If you have an isolator, connect the charger to the isolator and feed the wet cell batteries through the isolator. The isolator will drop the battery charging voltage by around 0.7V. If you don't have an isolator, charge the wet cell batteries and then insert a Schottky rectifier diode in the positive wire between the charger and the wet cell battery positive post. This will drop the battery charging voltage by around 0.4-0.5V. Try a
https://www.digikey.com/product-deta...LGOS-ND/918594 rectifier diode. This will allow 25A of
current during power restored charging. You can probably use 10 ga wire connected to the charger cord, crimped to the rectifier pin (right pin looking with tab down), and then another wire connected to the other pin or tab with the hole. Ideally the tab would be connected to the battery terminal so the rectifier is cooled via the terminal. Make sure you keep the connections insulated and don't let the rectifier tab touch another conductive surface other than the battery positive.