I am reconditioning a 12v lead acid battery, and a process I am trying requires me to remove aprox 2.5 to 3 oz of battery fluid from each cell. Before I do this, I'd like to know how to dispose of the removed fluid? Can I just neutralize it with baking soda?
What you're removing is ~28% sulfuric acid. Dilute your 18 oz with a quart of water, you can then neutralize it with baking soda with little difficulty. Wear rubber gloves and goggles and add acid to water in small amounts while monitoring the temperature. Have separate bucket of water nearby for yourself in case you get acid on your skin.
Are you not planning on putting the acid back in the cells after you recondition them?
Or are you planning on replacing it with new electrolyte? Where are you getting the new replacement electrolyte? Does the source not have a recycling system?
Can you take the electrolyte fluid to a place that sells (and recycles) auto vehicle batteries? They are prepared to handle the material properly as they deal with it every day.
One way that is relatively safe (because of the small amount of acid you need to get rid of), is to dilute it very very much. I've done it it the past and the possible dangers are low. REMEMBER TO USE RUBBER GLOVES AND EYE PROTECTION.
Just add the acid gently to a very large amount of water (eg 5-10 liters of water). Then you can possibly dump it even in the sewer.
Note that I'm suggesting that only because you have a small amount of acid which is clearly not worth it to pay someone to dispose it "properly" for you.