Installed a system on my batteries, believe it's made in Germany
. A bit more expensive but quality of components is excellent and easy to add extra batteries and/or different types of batteries. The system is modular so spacing of fill pikas doesn't matter.
Because of space constrictions, two of four batteries required pulling the batteries out to service
. Of course that meant I wasn't as religious as I should have been in keeping the electrolyte up and shortened the batteries life. Installed the watering system and keeping the fluid at optimum level is just a few squeezes on the bulb pump. The system would have paid for itself many times over if I'd done it when I bought the boat.