Sunday, March 30, 2014

Product review: Bolkin S-100 2600mah Portable USB Power Bank External Battery Charger Pack

This is small size battery (4" x 1" x 0.875") with one port. It weighs 2.5 oz. The package includes a charging cable with 4 tips (mini USB, micro USB, Apple connector, and a round connector I don't recognize). I find this size battery very handy to have in my purse for emergency power when my phone runs out of juice. The battery is rated as 2600mAh. Since some power during charging is lost to inefficiencies (such as heat) it will provide approximately 2210 mAh.

I tested Bokin 2600 mAh with Samsung Nexus phone and iPad Mini tablet. For those who are interested in the bottom line this battery pack worked consistently with both devices, charging both device at a slightly below average speed I have seen for chargers with this capacity.

I run the same set on tests on each battery pack I own, so I can compare them to each other using "apples to apples" comparison. This set of tests allows me to provide unbiased comparisons between different external batteries. I am including the details of the tests below for those who want to see the nitty gritty.

★ To prolong battery life

Li-ion batteries do not need to be fully charged nor is it desirable to do so. In fact, it is better not to fully charge, because high voltages stresses the battery. Li-ion should never be discharged too low. This is why battery manufacturers typically ship batteries with a 40 percent charge. The low charge state reduces aging-related stress while allowing some self-discharge during storage. If you plan to store the battery without using it apply a partial charge before a long storage period.

★ 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 current varies based on what the device requires and what battery provides. This communication happens using different protocols depending on OS. Starting with Android 4.21 Google adapted the Android 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
AC charging rate ----- 3% change in charge in 10 minutes
current monitor: ~~~~~ 0.85A and 5.02V

✔ iPad Mini Tablet
AC charging rate ----- 2% change in charge in 10 minutes
current monitor: ~~~~~ 0.92A and 5.05V

★ Summary
This is a nice battery to have on a go. Although not the speediest it perform reasonably well for its size.

You can find it on Amazon by following this link.

Ali Julia review ★★★★☆

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