Batteries need to be cool and ventilated from the explosive gasses they generate, specially the flooded types; therefore the engine
compartment is not the best place.
If you have an enclosed compartment, how would you ventilate it? Or do you?
A small intake grill
on the cabin
side to suck in cool air while a small computer fan blows it towards the engine
compartment through a hole in the bulkhead?
What if that fan blowing is then, inside a flexible duct, directed towards the alternator
to keep it cooler also, but with the danger
of igniting those explosive gasses from the batteries?.
Or the fan blowing into the duct, towards the outside of the vessel like a bilge
blower which makes another hole for water
to come in ?.
If this venting duct is combined with the existing bilge
blower duct hole, some of this air/ gas mixture will settle down the bilge duct into the engine's compartment and deep bilge anyway, so why bother doing that.
The batteries could be charging
from several sources; shore power battery charger
, engine alternator
and even solar panels
and wind generator
, which is my case for 6 batteries in that enclosed box space.
In all these cases, the batteries would benefit from being ventilated since they will generate heat and gasses while being charged.
What other ways you ventilate your batteries?
Many electronic gadgets reside near batteries in most boats and that is the case in this compartment.
Things like monitoring gauges, Ammeters, Voltmeters, ACR, also 1-2 both switches, other switches, buss bars, shunts, fuses
and many connections that will corrode faster if all those corrosive gasses are present.
What do you do to try to avoid explosion, heat and corrosion