I want to make my device portable and looking for portable power. I read in the specification that my Raspberry Pi 2 Model B needs 5v and 1.8A output for work. I have a number of power banks that have next outputs: 5v and 1A, 5v and 1.5A and can buy 5v and 2A or 5v and 2.1A. But I can't find 5v and 1.8A. Powerbank with which output is better for my Raspberry Pi 2 Model B? Is it enough my 5v and 1.5A or I have to buy more?
As others have mentioned, you only need the right voltage (4.75v to 5.25v), but you need the right amperage for your workload. For example, I recommend getting a power supply rated 2A and above for heavy computation and an external hard drive. A phone charger rated for 1A or a bit lower will be sufficient for a Pi monitoring temperature around the house.
The Pi will only draw the current it needs, so a high-amperage power supply is not really a problem.