There's definitely one thing I'll never quite get about other shops... especially west coast places: Why are there so many cars basically stacked on top of each other or otherwise right up on other cars? Especially customer owned cars?! This is a recipe for disaster no matter how many other precautions are taken.
I wouldn't even take a customer's car if I had to cram it in with a bunch of others for extended periods. At the end of the day, battery repair/refurbishment work can be dangerous (especially if you don't know what you're doing), and almost inevitably some kind of accident is going to happen. Best to not ruin millions of dollars worth of customer vehicles when it happens and
potentially not have sufficient insurance to cover those losses.
In my case, nowadays we usually keep customer vehicles that will be here more than a day in their own area, at most a couple at a time, that's pretty well partitioned off (two 12" block walls) from where we do any battery work (besides installation and removal, of course). Plus our entire 30,000 sqft space is sprinklered, tested to ~1800 GPM... enough to slow down any potential battery fire and completely squash nearly any other kind. Fire department is also 0.6 miles away. On top of that, currently have something like $10M in liability insurance, at least half of which is available for any losses to customer property in our custody.
I can't imagine being careless enough to a) allow such an issue to happen in the first place to the extent of destroying dozens of customer vehicles, and b) if, God forbid, something like that were to happen, not having enough insurance to cover any losses to clients. Anything less is just wrong.
You'd have to be crazy to leave your vehicle with them and just be like, "Welp, third time's the charm!"