Enclosing a battery charger in any kind of box is a real bad idea, especially one that has zero ventilation (not that you would actually able to do that with out cable glands, though I have seen dumber things than that done aboard)
If the manufacturer thought it was worth the trouble they would likely have provided some manner of thermal compensation charge control (hence smart) that might also provide a unit shutdown for any range of operational temperatures deemed excessive. This would happen well before any possible point of combustion. The truth is you can easily damage even destroy a lead acid with a regulated charger in a month or less if you are completely unaware of what current
actually represents, which is heat. This is especially true for automotive starting batteries which is what many people have aboard in spite of the fact that they believe they are deep cycles,
anyhoo here is the math:
2.5 amps trickle at 14.2 volts=35 watts
2 typical starting/deep cycle batteries rated 100ah each for 200ah total capacity. (5 hr rate)
2.5amps * 24 hours= about 60ah a day
Capacity 200ah/60ah=3.34 days
Add some 20% for losses 3.34+.67 = 4.01 days to 100% SOC
And note that, this is starting with a "trickle" current
which invariably won't happen because the charger will do what it was meant to do which is to charge the battery up ASAP.
And yet people will leave these chargers on continuously for months, heating
up the plates, boiling off electrolytes needlessly and losing both capacity and battery life all the while. A true tapering 3 stage should back current down to roughly 500 or less milli amps or .5 amps.
I have been working professionally with UPS, DC-DC converters, MPPT
, PWM SLA, LA, Li-Ion, NiMH and occasionally more exotic chemistries for about 20 years in mission critical and telecomm system power applications. When I do a power design for a yacht there are no troubles, period.
some people just like to fiddle about endlessly and some to enjoy sailing with the confidence of knowing that their navigation
systems are supported by an excellent DC power design.