I thought to have made a big deal by buying a Xiaomi 20800 mAh Battery Pack at the end of last month at Transcom costing around Rs500. The Battery Pack has failed all tests: How to identify-fake-xiaomi-power-bank. On the website aliexpress, the fake one I bought is less than half the price of the original.
Therefore, being fake and quite cheap, I could not resist to inspect the internals and learn about which type of Lithium cell/battery is being used, the warranty being inexistant in that shop. Upon pushing from top to bottom, it ejected quite easily, I searched for the charging IC on the circuit board and I was surprised of its contents. The fake Xiaomi 20800 mAh Battery Pack contains a battery holder, 8 2600mAh 3.6v LiPO/Li-ION cells, a battery holder, a small front plastic cover a cast Aluminium side circular rectangular cover and two black double-sided tape plus a USB-A 5.0v to 3.6v and 3.6v to 5.0v micro USB-B converter.
Therefore, being fake and quite cheap, I could not resist to inspect the internals and learn about which type of Lithium cell/battery is being used, the warranty being inexistant in that shop. Upon pushing from top to bottom, it ejected quite easily, I searched for the charging IC on the circuit board and I was surprised of its contents. The fake Xiaomi 20800 mAh Battery Pack contains a battery holder, 8 2600mAh 3.6v LiPO/Li-ION cells, a battery holder, a small front plastic cover a cast Aluminium side circular rectangular cover and two black double-sided tape plus a USB-A 5.0v to 3.6v and 3.6v to 5.0v micro USB-B converter.
The IC has an unknown code which is JY 311 NOS1A1 1526 whose datasheet is unavailable by Google. The eight Lithium cells are arranged in a parallel circuit so each 2600 mAh cells add up to 20800 mAh for an output of 3.6v. In theory, it should last more than 10 hours at a discharge rate of 2.0A.
Though Lithium cells are difficult to charge due to the different technology of each Lithium Compounds utilised depending on the particular needs of storage capacity, discharge rate and stability/safety. Complex circuitry is needed to charge at constant current, ie 0.7C, the cell is deemed charged when the rate of change of the voltage differs drastically from the initial rate of change.
Though Lithium cells are difficult to charge due to the different technology of each Lithium Compounds utilised depending on the particular needs of storage capacity, discharge rate and stability/safety. Complex circuitry is needed to charge at constant current, ie 0.7C, the cell is deemed charged when the rate of change of the voltage differs drastically from the initial rate of change.
I have another lithium charging circuitry having a solar connector but it expects two cells in series. Other tests are needed to stress the components.
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