power a device that takes a (1.1m? 3.5mm? the normal bigger one) 12v 6amp input

Same thing like this cable: https://www.amazon.com/12-Volt-Power-Supply-Standard/dp/B009ZZY28M except instead of 100v input AC it needs to be 12v DC (that a car can supply.... i think they go up to 10 amps?)

The one you picked charges at 800mAh, so it'll take nearly 3 hours to charge a 2200mAh battery, and you won't be able to tell what it's doing.

You can get the $20 DC version, if you've got a 12 power supply of some sort, like old PC or laptop power supply. Or you can get 12v DC power supplies designed for the job

The B6 isn't even a 'good' charger, it's a cheap clone of the $50 DC chargers everyone used to use before it came along. It's popular because it's cheap.

You'll have a charger for many years, so while you could manage with a cheap one, you'll end up buying a better one sooner or later.

I'm considering this one Amazon but the thing is I don't know if the circular connector is the correct size. I have so many of these connectors sitting around the house but either they don't fit some of the electronics or they are not the correct voltage/amperage. Is there some kind of system like SAE/Metric or is it unregulated and manufacturers just make whatever size adapter for their product like Apple?