Perhaps a cautionary tale, perhaps some folks were already aware…
My wife has a MacBook Pro assigned to her for College work, which lies unused during the summer break, well… it turns out not such a good idea to leave it off and not charging.
The MBPro will no longer charge, nor will it start up. According to the bods over at Apple Discussions leaving the Mac uncharged for months can result in this, whether via damage to the battery or a safety cutoff within the Mac. I have to now get it through the College’s internal IT route to Apple’s service centre here. That could be months too…
And yes, I’ve reset the SMC, left it charging overnight, checked and swapped cables and chargers, changed the ports and sides the charger connected to. I even left it warming in the sun for a bit…
I think this may be good advice in general. I have an old Garmin Forerunner 620 GPS watch that worked fine but was losing battery life. I replaced it and put it in a closet for 18 months or so. I recently wanted to give it to a friend, but it won’t start up at all, no matter how long I charge it. It’s actually the second one of these we’ve had that happen to—Tonya lost hers in a string backpack for years and when I found it, it was dead. I’ve thought about trying to replace their batteries, but it doesn’t look easy.
You can leave your mac off for many months if you charge it to 50% before you leave it turned off. You have to store it in a environment that’s less than 90° F (32° C). I have a 2014 MacBook Pro that I do not use, but I want it to be ready as a backup machine. I turn it on every six months and charge it up to 50% again. For the last 4 years, I have done this.
Perhaps it’s more recent Macs, this is a 2020 model. My wife’s was 100% charged in May, and Ireland has had one day (!) over 32 Celsius in the interim. Perhaps, in the context of the return of MagSafe, it relates to charging via USB-C.
Anyway it was news to me, I’ve always been of the ‘if you can, charge’ school.
My MacBook Pro 2012 running Catalina was accidentally left running on battery a month ago and died. After charging, it would start but the screen stayed dark. I charged it but same issue. I then plugged it in for some days, and now it has mysteriously returned to life.