In recent years, due to rapid development of lithium battery, remaining battery capacity on portable products has been evaluated by voltage measurements, however, their relationship varies according to discharge rate, temperature and battery’s aging degree. In this way, error rate can reach 50%. Because of growing market demand for longer use time, more precise solutions are required during design. Using smart battery fuel gauge IC to measure battery’s charge or discharge capacity is able to precisely evaluate battery level.
- Design requirements of smart battery for POS machine
Based on customers’ requirements and specifications, information share between smart lithium battery pack and POS host devices can be achieved by integrating smart battery fuel gauge of communication protocols, lithium battery and safety protection performance into solution. In this way, reasonable, efficient and safe battery management solution can come true. The whole solution’s design should be aimed at most perfect integration with main units, and conditioned on safety guarantee of battery, batteries and the whole system, together with compliance with relevant design and certificate regulations. Meanwhile, in order to ensure safety and reliability of the lithium battery, multi-layer protection should be taken on interior battery pack to prevent them from damages arising from overcharge, over discharge or short circuit.
- Smart battery solution for POS machine
- PCM: a protection circuit designed mainly for rechargeable smart battery pack. Because of chemical characteristics of lithium battery, protection functions like smart battery level calculate, overcharge, over discharge, short circuit, over current, etc should be provided to avoid fire and explosion.
- Protection IC: constantly monitors cells’ overcharge, over discharge, short circuit, and over current to ensure cell’s safe, stable and efficient work.
- Over current protection (PTC): mainly target for secondary protection function. PTC can recover fuse and has dual functions of over current protection and auto recovery. PTC can avoid battery from over heat discharge and occurrence of unsafe high current.
- 103450 Li-ion cell(SANYO)
- MOSFET: play the role of switch during circuit protection to guarantee load voltage can neither rise nor drop.
- Capacity management chip (BQ26500):
A fully functional capacity test gauge has two ADC, one testing voltage and temperature, and the other testing capacity and charge sensor. In addition, it has a mini processor responsible for indicating the remaining state of capacity and run time to empty. Main unit can always seek these information from capacity fuel gauge and inform users of the battery information.
- Battery package: plastic enclosure
- Diagram of smart battery solution for POS machine:
- Picture of smart battery for POS machine: