I have at car usb charger. It has 2 ports and is rated 2.1A when one port is used and 1A when both ports are used. I attached samsung tablet (N8000) witch requires 2A output. So, tablet isn't charging. Then i plugged my phone (S5 neo). I drive around with waze turned on (about one hour). My battery does not charged. It even discharge by about 3 or 5 percents. I tried both ports.
Then i found my old 1A charger with single port. That charger charged my phone, with waze turned on. From 80% it goes to 100% within one hour. In both cases i used the same cable.
So - how i can test charger output amperage? Do i need special equipment or it can be done with multimeter?
Edit: How I can test if charger really can supply rated amperage? So, how to test its limits ?
Edit2: Found this article: http://www.deeptronic.com/variable-dummy-load-for-power-supply-testing/ and I try to build that.