I have obtained a couple of dead-battery Dyson vacuums in recent years. Aftermarket replacement batteries are available and so far, so good. The ones I installed offer somewhat increased capacity over the originals and performance is as good as I would expect. Of course aftermarket lithium ion battery packs are a crapshoot at best, so I stuck with ones that published at least plausible capacities and had a reasonable number of good/non-fake reviews. Given the price and lack of availability of OEM packs I'd say go for it.

I bought one for my girlfriend's Dyson (v6, I think) - which had terrible battery life from day one, and got worse over time. She was very dubious about it, but it worked a lot better than even when the Dyson was new. Still not great, but better than before.

Eventually I persuaded her that a Henry was the way forward. She bought it and now knows what I mean - I have one as a "garage/DIY" one and another as the house vacuum. There's a reason why professional cleaners in the UK use them!

Yes, I bought a brand called Vanttech [1] for my Dyson V6. Not only has it worked perfectly, but the new battery pack also lasts longer than the official Dyson one. Much cheaper, too, of course.

[1] https://www.vanttechbatteries.com/products/for-dyson-v6-upgr...

Yes, Dyson was out of stock, when the battery in my V8 died so I felt forced to buy an aftermarket just to use it. More amp hours than the OEM (or so they claim), and so far working great. The filters that came with it don't fit as well as the OEM ones though, they are falling off when I hold the vacuum wrong.

Yes. I bought an aftermarket v6 battery with increased maH over the original, but with no 3 stage blue led charge level indicator (just one led) but it definitely lasts longer.