1) Design requirementsAccording to the requirements of consumers, in order to realize the Information Sharing between lithium battery pack and the host engine, and rational, efficient and safe battery management, we designed a host supporting lithium battery pack to integrate Lithium Battery and Battery safety protection performance together. Based on the safety of Batteries, Battery packs, and the entire system in this whole design program, the design meets the requirements of related design and certification regulations. Thus, in order to ensure the Safety and reliability of Lithium Battery, we design Multi-layer protection in internal battery pack to avoid short circuit or damage caused by Overcharge, over discharge of Lithium Battery.
2.Circuit design requirement
- A.single battery overcharge protection voltage: 4.28±0.25V
- B.single battery overcharge recovery voltage: 4.08±0.50V
- C.single battery over discharge protection voltage: 3.00±0.08V
- D.single battery over discharge recovery voltage: 3.00±0.08V
- E.Combined battery over current protection (10ms):1.5~3.5A
- F.Battery over heat protection (recoverable): 70±5℃
- G.Finished battery can be protected from the harm of short circuit and reverse charge.
4.Battery dimension design requirement: Referring to the host shell，and can be customized by customers’ requirements.
2) The designing scheme for mobile payment terminal Lithium Battery
1. Protection Board (PCM): designed for rechargeable lithium batteries to protect circuit, the protection board needs to provide smart power calculation, overcharge, over discharge, short circuit, over current protection to avoid the hazard of burning and explosion because of its chemical properties.2. Protection IC: The main function of the designing scheme is to protect the chip, we use high intelligent battery management system (SBS) to manage battery safety and electricity, and constantly monitor the situation of overcharge, over discharge, over current, short circuit occurring, so that the chip can operate in a safe, stable and efficient condition.
3. Temperature switch: mainly for temperature protection design. When the temperature of the battery reach to 75 degrees due to other usual problems, the temperature switch will achieve to over-temperature protection, when the temperature drops, automatic recovery.
4. Li- Polymer cell : 402060P/450mAh/3.7V
5. MOSFET: acting as a switch in the protection circuit, and balances the voltage across the load.
6. Battery Pack: PVC thermal shrinkage
7. The schematic of mobile payment terminal Lithium battery