for recycling old notebook LiPo cells, mainly 18650s, I've bought some of those BYOB (bring your own batteries) banks from eBay. I also tried to research how one gets to know the internal resistance of a battery.

So If I understood correctly I'll get the internal resistance by measuring the battery voltage with and without a known load and use the following formula:

The batteries I'm using are sanyo ur18650F, typical Capacity is 2600mAh and charging current is 1.75A per cell. That's way more the powerbank is able to deliver, as it seems. Input is rated 1A. So what happens if it can't deliver more?

http://www.batteryonestop.com/baotongusa/products/datasheets/li-ion/sanyo-ur18650f-26a.pdf