Wow, I knew it would have less run time, but this is like half the capacity of the original battery. I just bought my Dyson V15. I've only vacuumed and charged the original battery about 8 times, so my original Dyson battery is in new condition. To get the most accurate comparison between the two, I fully charged both batteties overnight. The next day I used a trigger lock to turn the vac on, and set it to Boost. That eliminates any influence from beater bar load. So, just vacuuming air on a counter, in boost mode, the original battery ran for 6m23s. I repeated the same test with this battery and it ran for 3m28s. This battery is less expensive, but it isn't lighter. I would have at least hoped for a lighter battery, if it has less capacity, but no joy there. If we look at this strictly as dollar spent per usable minute of vacuuming, then this battery really doesn't compete. I think the original is $170, and two of these kastars would be $194... I recommend shopping all over. I've seen V11/V15 batteries for as low as $45 from China. It's likely that this seller is buying these for $45 and selling them for $97. $45 would be a competitve price, but $97 really isn't. The numbers are the numbers. Good luck.