[Gary S] Installed second battery (in parallel) in my 5th-wheel. Only space available was constructed almost air tight. Battery says to install in ventilated area. How much ventilation is needed?Any other problems I should anticipate/head off?
[Vern M.] You don't say how far apart the batteries are. They should be as close (next to each other) as possible. If not, the wires connecting them need to be as big as possible (i.e. 6 guage at least). The reason is to allow as much current to flow between them as possible.
As for ventillation, any is fine that allows some air flow. Especially exiting above the top of the battery. The ventillation need is to dissipate they hydrogen vented by the battery in normal use. Hydrogen is lighter than "air."