Odds are if you use a normal battery nothing will happen but that does not mean nothing could happen.

The worst is if you have a overcharging issue you could vent a lot of hydrogen gas into the interior and it could ignite.

Also we had a GTO that had a battery in the trunk with no vent or case and it did rot the floor of the trunk out with the fluid that did vent from the battery.

 

Well ended up going to another franchise and they just ran a flexible hose from the vent port of the battery to the vent tube in the car. There was still a debate about whether venting was necessary since the new battery was "sealed" and according to some does not vent hydrogen- just heat, hence the port. Anyways, this should do it whatever the actual need is.

 

Maybe the batteries in the trunk do not need external venting. only those in the passenger compartment do.

 

in an hhr wagon the trunk IS inside the pass compartment..

 

Good deal. If the battery has a vent port, then you want it to vent to the outside. No matter what it's venting.
Sounds like you are good to go and have the issue resolved.

 

Maintenace free, they put 5 years of water, but in hot or very cold areas sometimes maybe 3 years warranty just look at the pro-rate not much of a warranty.

 

If a charging system is right most batteries will surpass the 5 year mark. Often batteries will fail due to poor charging system either not charging enough or over charging and boiling the fluids out.