Znter S19 9V 400mAh USB (Black-green)

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Official specifications:
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This is a usb rechargeable 9V, it cannot be charged on a 9V charger.

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The B battery only had half capacity, this makes me believe the cell consist of two LiIon cells in parallel and one of the cells was not connected in the B battery. For this reason I have shown the results for the A battery above, i.e. the battery with full capacity.

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Behind the small hole in the bottom is a led that shows red while charging, it will turn off when the battery is full.

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To charge the battery any (phone) charger with a micro usb connector can be used.

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The output voltage is about 9.5V from start to finish and nearly independent of load. This means a battery gauge will show full until the equipment stops working.
One battery has a bit about 300mAh and the other a bit about 150mAh. It is interesting to note that the lowest load do not give the highest capacity/energy output, the boost converter is using a higher percentage of the energy at low load.

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Charging current is measured at 5V and starts at 500mA, charge is terminated at 50mA.
The boost converter will discharge with about 0.1 to 0.2mA, when the LiIon cell is below to 2.5V the current will drop to below 2uA.


Conclusion

This battery is not the most impressive 9V I have seen with one battery partly defect.
It is a neat solution in some cases:
1) Charge (replace) batteries at regular intervals, to avoid them running down, i.e. do not need the fuel gauge.
2) Need 9V battery with high voltage.

Do not use the batteries for low power applications, the boost converter will drain the battery in 6 to 12 months.



Notes and links

Disassembly

How is the test done and how to read the charts
Compare to other 9V batteries: Alkaline/NiMH/Lithium/other