USB battery box 2x18650

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I found this box on ebay, specifications is something like:
The box is an update of this unit.



How does it look

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The box arrived in a envelope without any accessories.

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The box is fairly compact. It is controlled with a switch on top of the box. There is four blue leds around the switch.
A press on the switch will turn the output on, a double click will turn the led on or off, there is no special "battery disconnected" state.

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This hole is not used on this version of the box.

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All connections are placed in the same end, mini usb for charging input and normal usb for output. There is also a led for flashlight usage and a led showing when the output is on.

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To replace the batteries, slide the bottom off the box. The batteries can be up to 69.7 mm.

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Measurements


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I did the load sweep up to 2A, the box did not turn off its output, but keep the voltage close to 5 volt all the way.

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With a 1.4A load the box can keep the voltage up for about 2 hours.

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Reducing the load to 0.5A, extends the runtime to nearly 7 hours and the box has a very good efficiency.

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load3.5ohm

With 1.4A load the noise is about 180 mV

load10ohm

Reducing the load to 0.5A will reduce the noise to 60mV


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Charging is with constant current and measuring the voltage with the current turned off. Because the CV part is missing, this will give a fairly fast charge, but to fill the batteries completely the charger needs to go above the maximum voltage for the batteries.
It works, but I will recommend charging the batteries in an external charger.

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With all the test batteries the charge voltage is above 4.3 volt, this is not very good.



Conclusion

The box works is good for supplying current and is easy to use, but the charging circuit for the batteries is not very good.
The hysteresis on the battery indicator leds, makes it better at indicating battery voltage.



Notes

Read more about how I test USB power supplies and chargers