Originally Posted By: BerlinettaBoxer
I had a bad experience with AAA batteries but I think it was more due to incompetence on the tech's part than the fault of the battery. My dad was borrowing my car, and the battery died. He called AAA to come and replace it (I wasn't around otherwize I would have done it myself). They come out, replace the battery, still doesn't start, wrong battery. So they tow it to a shop, who also installs the wrong battery but it starts now so its not obvious theres a wrong battery. I figured it out when I had replace it relatively early and noticed the battery they put in was half the size of the battery box. Honestly, how hard is it to figure out the right battery? The computer at WalMart can do it!
I think it's reasonable to conclude they used whatever battery they had available. Most places won't carry every size out there but will find an alternate that will fit. This yields mixed results; I used to own a 00 Bonneville that had one of those special sizes that nobody carries. Had a shop throw in another group number of similar size but it turns out that special size had an important feature missing on the more common battery- it had an orifice to connect a vent tube to which is required to vent gasses outside the cabin as the battery was mounted under the rear seat. Without that tube connected, both terminals badly corroded in short time, so there are important reasons to choose the right battery for the job.
Be aware that some cars specify different batteries depending on the region it's sold in. For example my 01 Frontier specifies a group 24 only in Canada, but in US a smaller battery is installed, presumably to save money, about half the size even though it has the large battery tray. Size isn't as important as one would think, A 12 volt lawnmower battery will still start a car, but the reserve capacity for operating accessories with the engine off will be compromised as well as cold weather starting.
In short, the battery tray isn't a reliable indicator that you have the right battery for the reason mentioned above. There are a lot of variables to consider before placing blame squarely on the technician. But certainly if you can do the work yourself, do it, this ensures you get the right part and not something that just "works."