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Earlier reviews showed that Tronsmart's Presto Quick Charge 3.0 battery pack was compatible with Qualcomm Quick Charge 3.0 devices such as the Xiaomi Mi 5. This same Qualcomm Quick Charge 3.0 protocol is supposed to be backwards compatible with devices supporting earlier Qualcomm Quick Charge technologies. Unfortunately this does not seem to be the case for the ZTE ZMAX Pro when used with Tronsmart's Presto charger's USB Type-A port which supports Qualcomm Quick Charge 3.0.  The ZTE ZMAX Pro claims to use Qualcomm Quick Charge 1.0 from the MetroPCS website but we don't see the phone listed on the Qualcomm website.

First, we observe the current and voltage that the charger provides to the ZMAX Pro. The Voltage varied between 3.9 and 6.2 volts, which is not unusual. The current, however, was merely 330 milliamps to 500 milliamps. This results in a range of power from 1 to 3 watts. This is extremely low for a Qualcomm Quick Charge charger, especially considering that the battery was almost depleted at the time of testing. 

We also checked to see how long it would take to charge the phone from 1%. 

Our fears were confirmed where after 40 minutes it had only charged 7%.

Nonetheless, we decided to continue the test to see just how long it would take. 

After five hours of charging and a battery that was still only 3/4 full, we decided to call it quits, as the results thus far showed how poorly these two devices worked with each other. The Tronsmart Presto charger charges the ZTE ZMAX Pro at an abysmal rate. We've seen the Presto work well charging other devices, and we've also seen the ZMAX Pro charge at faster rates with other chargers.