First the ridiculously priced battery packs. PLEASE NOTE THAT THE PACK CASING WAS NOT MADE TO BE OPENED AND REASSEMBLED. The case is a pain to split apart however the casing will be fine you just can’t snap it back together. If you are patient it is straightforward, a screwdriver and plastic scraper were what I had used. I am fine with that and will reglue it or use an RTV silicone or gasket material. The pack consists of 4 18650 batteries that are very inexpensive and look to use a standard RC car battery pack connector. I do not have any to verify that information though.
Second I prefer the Lincoln Viking 3350 Auto Darkening Filter over the Miller ADF and was pleasantly surprised to find out that the Viking fits easily into the Miller’s retaining rubber holder. The opposite is almost true if you grind down the 4 clips since the Miller is thicker than the Lincoln ADF.
Third is just a tip - mine had a slight odor to it that I am uncertain of its nature but it was used so who knows. Washing the hose wasn’t quite enough to clear it so I found you can fit a dryer sheet on the OUTSIDE of the HEPA filter and get a very cheap air freshener.