Q: I have an iPhone XS, XS Max. Does the PowerPack 10K portable charger fast charge my phone?
A: No, it will not. Specifically, the PowerPack 10K does not support USB Power Delivery (PD) fast charging technology in the iPhone X, XS, and XS Max. By Apple's definition of what can be considered fast charging, the minimum rating would be an 18W USB-C, PD charger. You can take a look at the official Apple guidelines/instructions here.
But the PowerPack 10K will charge your iPhone faster than the stock 5-watt (W) iPhone square plug. Based on our own usage and testing, the iPhone can be recharged at around 10-12W with the PowerPack 10K, which is roughly 2x your stock iPhone plug. For the average consumer, this is more than enough for everyday use. Keep in mind that in order to fast charge your iPhone using Apple's guidelines, you may have to purchase a new USB PD wall plug and a USB-C to Lightning cable. However, the difference is charging speed between 18W vs 12W wall plugs is not very noticeable in day-to-day use.
If you are interested in learning more about fast charging your iPhone, please read this short guide we put together: Fast charging your iPhone.