I've noticed that most warm air intakes position the filter next to the battery. Bcause car batteries release acid gas, won't this gas be introduced into the engine through the intake? And will this lead to corrosion of internal components?

 

Interesting point, but I doubt it's a problem... the engine encounters much more concentrated acids than H2 vapor (which isn't necessarily acidic, it's just flammable) as by-products of combustion. The biggest problem with intakes is air filtration--if the air filter is letting junk through, or there is a vacuum/intake leak allowing unfiltered air inside the engine, it will allow more dirt/particles into the engine, which usually shows up on an oil analysis in the silicon dioxide levels (I think they use that to estimate how well the air filter's doing)