M_Boats: electric, hatch on M17

I am going to add a small solar panel on top of the hatch cover - is there an electric wizard in the group, I was told today that to protect the battery from boiling dry, I should solder in place a 14.4 volt zenner diode between the solar panel and the battery to prevent overcharging when at the dock or on trailer for a few weeks. Apart from the back-feed diode which is also needed when no charge controller is used. Thanks, MC