The name says it all the Charge 3 can charge the Puls 2 can't otherwise it would probably be called Charge ;-) otherwise I agree with Theosteiger's answer.
The USB port on the Pulse 2 is only used to charge the battery of the Pulse itself and cannot be used to charge a smartphone. For this, a USB socket type A would have to be available as a power supplier. Both types of socket are available on chargers: Type A (power supplier) plus mini-USB (charging from the mains unit).