I am in the habit of swapping batteries between my cars depending on what I will be driving, but I do have a few "absolutely dead" batteries in the back of my shop. I first tried this with no battery and had "0" results, so I wasn't expecting much. I went and grabbed an absolutely dead battery from the back of my shop, dropped it in my 396 Camaro and hooked up this 1500 Amp Audew jump box. Lo and behold, I kid you not, this cranked the car faster than the normal Interstate or whatever I have in there..., I started it, and ran it for about 5 minutes, then started it again...., I am amazed.
I have no idea how long this will last, but with the Lithium Ion battery, I'm guessing it should be good for awhile.
Right now if you go to www.Audew.com, they have better prices, no tax and free shipping on their boxes. Disclaimer, they are made in and manufactured in China, which I do not like and was delivered directly by Amazon (which I can not stand), but the 1500 amp was $69 and they have a 2000 amp, which I will be ordering momentarily for $89. This is without a doubt the best jump box I have had in my entire life. Small, compact and easy to store.