I can't imagine accuracy is that close in most. I bought a rather large digital meter from an electrical warehouse supply account about 20 years ago. The meter cost around a 100 bucks then(probably better meters for half today), and takes a 9volt battery. It's the only meter I've kept on the boat(second boat), and it never fails. The screen, led(?) is a little weird., I've spliced new leads on, and I think it's accuracy is funky, but it's consistent.

I'll check the batteries in another month. They were charged in November. Any that are under 12.5-4 are probably toast(you can still use them-less storage-your choice).

When I pull out the 12.4 suspects - if I find a date sticker - the battery will be about 5-6 years old.