Confirm which model of Dyson vacuum you have (like for me I have a V8 model) and find the battery adapter that matches. Like if you have a V6 and want to use your Bauer batteries, lookup something like "Dyson V6 battery adapter for Bauer batteries" - seeing as Bauer batteries are Harbor Freight's version of someone else's battery, you might need to do some digging to make sure you get the right one.

It's like 3 screws to take the OEM battery out, you put the battery adapter in its place (using the same 3 screws), and then slide the battery on and off just like your other cordless tools. It's pretty awesome.

Yes but I already had the Dyson vacuum, so rather than getting a whole extra vacuum, I got a $25 part so I can keep using what I have. Granted if someone has DeWalt batteries but no Dyson vacuum, of course go with the DeWalt vacuum over the Dyson.

You actually have to take the OEM battery out of the vacuum and it goes in place of the battery, and then you attach a battery to it.

Pretty much what u/MySweetUsername linked to, but you need to make sure you get the one that's specific to your vacuum model and is built to take the kinds of rechargeable battery that you have. Like for me I have a V8 Dyson and DeWalt Batteries, so I had to get one according to those specs. I think it's like 2 or 3 screws to take the old Dyson rechargeable battery out, and then the battery adapter attaches using those same screwpoints and screws. You can't use the original Dyson charger or hanging dock now, so when the battery dies you have to take the battery off the vacuum and put it on it's OEM charging station (and even without the battery the vacuum still won't hang on the wall mount), but it's a small extra step to greatly extend the life of an otherwise great vacuum.

For the folks on this thread that have a Dyson already, but the battery has shit the bed or is about to - you can get battery adapters so you can use DeWalt/Makita/Milwaukee/whatever rechargeable batteries with the vacuum. The adapter costs ~$25~$30 and installs very easily. I can get ~1.5 weeks use out of a smaller battery. Definitely a qol upgrade.