7.4V 1900mAh Intelligent Battery Design Solution of POS Machine

Foreword: (keyword: intelligent lithium ion battery) as the rapid development of lithium ion battery, many portable products utilize voltage measured value to estimate the remaining capacity of battery. However, the relationship between battery voltage and remaining capacity will change along with discharging rate, temperature and aging of battery. The error rate of this method may be up to 50%. The market has more strict requirements on products with long service time, so the battery design needs more accurate solution. Applying intelligent capacity survey meter IC to measure charging or consuming capacity helps provide more accurate capacity measurement in wider range of applying power grade.

Intelligent battery design solution of POS machine

Based on customers’ requirements and specification, design intelligent battery pack of handheld device to assort with POS machine and integrate intelligent voltmeter with communication protocol, lithium ion battery and protective performance into the solution, which can share host machine information with intelligent lithium ion battery pack and POS machine, and realize the reasonable, efficient and safe battery management scheme. During the design process of the whole scheme, take the perfect integration with host machine for direction, regard the safety performance of battery pack and the whole system as premise, and make the conformation of relevant design regulations and certification as first priorities. In order to make sure the security and reliability of lithium ion battery, the battery pack applies multi-protection inside to avoid being damaged by overcharging, over-discharging or short circuit.

Intelligent battery design scheme of POS machine:

1）Guard plate (PCM): it is protective circuit of intelligent rechargeable lithium ion battery pack. Because of the chemical characteristics of lithium ion battery, it needs protective function of intelligent capacity calculation, overcharging, over-discharging, short circuit, overcurrent and over temperature so as to avoid combustion, explosion, etc.

2）Protection IC: it is the chip has main protective function in the design scheme. The chip monitors the cell on the functions of overcharging, over-discharging, overcurrent, short circuit, etc. at any time, which helps the battery works under safe, stable and efficient circumstance.

3）Overcurrent protection (PTC): it is designed for secondary protective function. Restorable PTC fuse has dual functions of overcurrent protection and self-recovery. PTC of the product can prevent high-temperature discharging and unsafe large current.

4）103450 lithium ion battery/103450 Li-ion cell (SANYO)

5）MOSFET: it works as the switch in protective circuit to make sure that the voltages of two ends won’t be up and down, so that the voltage will be stable.

6）Capacity controlling chip (BQ2085): it is a full-function capacity survey meter with ADC of voltage and temperature, and ADC of current measurement and charging sensor. This survey meter has a microprocessor to work on capacity measurement, including massage of remaining state of capacity. BQ26500 product can also display run time to empty. The host machine can search for these information at any time and send them to the customer. It is very convenient for user to control battery capacity by using capacity survey meter.