Has anyone ever come across an optima battery having a funny smell while charging/in use? Recently got my hands on a yellowtop D31a (used) and have wired it in the trunk while keeping my red top under the hood. I didn't notice any smell while charging it prior to install. Hard to describe the smell, nothing overly offensive, but I want to be safe.

Any ideas?

Make sure its properly grounded, and nothing smells like its burning

i use a yellow top myself as a second battery, and i have never had issues with any odour coming off the battery.

when charging, it is imperative that you stop if you see any kind of vapour coming out of the sides of the battery. ...this is the only time i have seem / smelt anything coming off of one. if you do this, your battery will be toast alot quicker than it should be. and don't breath it in. its acid. lol

Thanks for the responses.

I have not seen any vapours of any kind so far.
I will see if I can make an improvement on the ground. But it does not smell like burning as far as i can tell.

i have 2 under the back seat in my explorer and i have not come across anything

I had a RT vent and overheat on me. It smelled like rotten eggs.

if it smells like rotten eggs it's the vent, the battery is getting too much charge.

Doesn't smell like rotten eggs.. More of a metallic smell

What is the system voltage with the car off and running at ~2000rpm? You can check the running voltage in park. When do you notice the smell, on the road or parked? What car is this?

I usually notice the smell 15-30 minutes into a drive. The smell seems to go away after the car is off for an hour or so. I believe I tested the voltage right after the install, with the car running parked. I don't have the greatest multimeter but I am pretty sure it was 13.5 volts or so. The car is a 99 grand prix, 3.8L. I had zero issues with smells or gasses prior to the yellowtop install other than the lights dimming quite abit. The extra battery fixed the dimming and the stereo seemed to run noticably better but the smell or gasses the battery is emitting worries me.

Thanks for the responses.