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Sunday, January 26, 2014

Product review: Mpow® 4.2Amps 20W Dual USB Port Car Charger


I have mixed feeling about this charger. On one hand it charges at a fast rate (there is only one charger that performed better in my tests) on the other hand the fit in the car charging port is a bit loose and had to be readjusted when we drove on rough roads. The speed of charging is very important to us as the charger needs to keep up with the power hungry Sygic app that we we use to navigate.

Mpow Dual USB Car charger is fairly long compared to some of my other car chargers (3.5" long) and provides up to 4.2Amps between its two USB ports. The USP ports are not labelled . The front of the panel lights up in blue to indicate that the charger is working, given the loose fit this light was key to know when to re-adjusted it. Its weight is 0.9 oz.

For those who are interested in detail of how I tested this charger I am including the details below.

➨ How I tested this car charger:

I have been testing various chargers for a long time, and people often ask me why results differ so much from charger to charger and often port to port. The results are different because they are affected by a number of factors. To help with a numerical explanation of the differences I began using a USB current monitor which shows the voltage and the current flowing between the battery and the device.

The amount of energy transferred from the charger to the device is calculated by multiplying voltage and current. Most of the chargers are 5V devices and most devices show the voltage very close to 5V. The interesting number is the current as it varies from unit to unit and from port to port.

The current varies based on what the device requires and what battery provides. This communication happens using different protocols depending on OS. Newer Android OS versions have adapted their protocols to get better performance from ports aimed at Apple devices. An addition variable that effects performance is whether a data cable or charging cable is used to charge the device. The charging cables short the two data connections together (rendering them useless for data transfer), but this fools devices to see the cable as an AC power connection, and thus accept the higher current of the charging source.

The 10 minutes test consists of charging each mobile device on each port of the battery pack for 10 minutes and measure how much each unit was charge in that 10 minute period. Since the charging speed is non-linear I start charging each device from approximately the same charge level. I use Battery App by Elvison to determine how each device recognized the charging source. 'AC' status means the charging is at full charging rate. 'USB' status indicates charging at a lower charging rate. 'Discharging' status means that the charging rate is below the power that the device is consuming so it slows down the discharge rate but does not re-charge.

➨ Test Results:

✔ Samsung Nexus Phone
Port 1: 10 minute test: ~~~~~~ AC rate ~~~ 10% in 10 minutes (charging cable)
Port 1: current monitor: ~~~~~ 0.97A and 5.17V (charging cable)

Port 2: 10 minute test: ~~~~~~ AC rate ~~~ 7% in 10 minutes (charging cable)
Port 2: current monitor: ~~~~~ 0.96A and 5.17V (charging cable)

✔ Nexus 5 Phone
Port 1: 10 minute test: ~~~~~~ AC rate ~~~ 6% in 10 minutes (charging cable)
Port 1: current monitor: ~~~~~ 1.19A and 5.17V (charging cable)

Port 2: 10 minute test: ~~~~~~ AC rate ~~~ 5% in 10 minutes (charging cable)
Port 2: current monitor: ~~~~~ 1.10A and 5.17V (charging cable)

I received this charger from the manufacturer for an honest review be it positive or negative. I like its speed but the loose fit required paying attention to the charger to make sure it is still plugged in.

You can find it on Amazon by following this link.

Ali Julia review ★★★★☆

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