Identifying Battery Cell Symbols and Layout
A back up battery cell or button cell is being used in cellphones circuit to back up the digital clock crystal oscillator. It used to maintain the clock at its real time status.
Its like when removing the battery of the mobile phone wont reset the settings of the digital clock that is being installed on a phone. Some phones without battery back-up like the old ones need to reset again after removing and replacing the battery. Its a big help to a digital circuits such high tech mobile phones circuit.
A battery cell is have two lead terminal which is negative and positive voltage output.
The metal can case of this type of battery is its positive (+) terminal, and the negative (-) terminal is the cap.
The negative is connected to a ground lines of a circuit while the positive is feed to a clock oscillator circuit. It has low power output voltage range from 1.5 volts to 3.5 volts. In mobile phones used about 3.3voltage output.
They are compact and have long life. They are usually a primary single cell with a nominal voltage between 1.5 and 3 volts. Common anode materials are zinc or lithium. Common cathode materials are manganese dioxide, silver oxide, carbon monofluoride, cupric oxide or oxygen from the air. Mercuric oxide batteries were formerly a common battery type but have been withdrawn from marketing due to their mercury content.
A back up battery may also damaged when due to degradation, corrosion and losses its voltage when being shorted or by liquids like water;
A damaged battery cell can be easily notice when a leakage occurs, its liquid chemical will flow out and can cause damages to a nearby components.
In a mobile phones you can determine when the back-up battery is weak, when try to set the time of the clock, then power it off and by removing the battery for a while and put it back again, when the clock stayed at its time where you set, it means that back-up battery is still working but, if it ask you to set the clock again it means that the back-up battery is not working.