Monday, March 10, 2014

Product review: amzdeal gimall Dual-port Portable High Capacity External Battery Charger Backup Power Bank

This external battery pack has 2 charging ports (1A and 2A) and 10000 mHat capacity. It has a nice black matt non-smudge finish and comes with a 9 inch charging cable. The battery itself is 5" long, 2.75" wide, and 0.625" thick. The battery together with the AC plug weigh 7.8 oz. 4 small LED lights indicate the charge level.

I tested GiMaill external battery pack with Samsung Nexus phone and Samsung Galaxy 7.7 tablet. For testing Galaxy tab I used my own charging cable (the package does not include any adapters).

I own a number of external batteries and to compare them I run the same set on tests on each of them, so they can be compared to each other using "apples to apples" comparison. This set of tests allows me to provide unbiased comparisons between different external batteries because I can compare based on numeric results of the tests. For those who are interested in the details of the test I include at the end of this review. For those who are interested in the bottom line this battery performed respectfully, falling in the middle of the pack.

★ How I tested this battery pack

I use a USB current monitor and a charging test to test each port. The current monitor 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 for Android devices 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 Galaxy Nexus Phone
1A port ~~ AC charging rate ----- 4% change in charge in 10 minutes
1A port ~~ current monitor: ~~~~~ 0.92A and 4.98V

2A port ~~ AC charging rate ----- 7% change in charge in 10 minutes
2A port ~~ current monitor: ~~~~~ 1.00A and 5.09V

✔ Samsung Galaxy 7.7 Tablet
1A port ~~ AC charging rate ----- 5% change in charge in 10 minutes
1A port ~~ current monitor: ~~~~~ 1.38A and 5.00V

2A port ~~ AC charging rate ----- 5% change in charge in 10 minutes
2A port ~~ current monitor: ~~~~~ 1.41A and 4.99V

★ Summary
It does not have many extras (no flashlight, no travel pouch, no adapters) but it has a nice capacity and performed respectfully falling the middle of the pack. Enclosed user manual was entirely in Chinese, but the external pack was straightforward to use and I did not need the manual.

You can find it on Amazon by following this link.

Ali Julia review ★★★★☆

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