1. Design requirements of lithium battery for medical equipment
Lithium battery for medical devices at present, most lithium batteries for medical devices are polymer batteries. Because of the excellent quality, excellent performance and high safety of polymer batteries, the batteries for medical devices are widely used in medical devices such as sphygmomanometer, wearable oxygen monitor, handheld monitor, wearable single lead electrocardiograph, beauty instrument, electronic cigarette, etc. For this reason, our company adopts A-type battery cell with good safety performance. The structure of medical instrument battery adopts aluminum-plastic flexible packaging, which is different from the metal shell of liquid battery. In case of potential safety hazard, the liquid battery is easy to explode, while the medical instrument battery only has small thickness and can be thinner. The thickness of liquid lithium-ion battery is less than 3.6 mm, which is a technical bottleneck. The thickness of medical instrument battery is less than 1 mm, and its weight is light. The weight of medical instrument battery is 40% lighter than that of steel shell lithium-ion battery with the same capacity and 20% lighter than that of aluminum shell battery. The shape can be customized, and the battery thickness can be increased or decreased according to the needs of customers. The capacity of medical instrument battery is 10-15% higher than that of steel shell battery of the same size and 5-10% higher than that of aluminum shell battery. The specific parameters are as follows:
Nominal voltage: 29.2V
Nominal capacity: 3.5 Ah
Charging voltage: 33.6V
Discharge current: 5A
Instantaneous discharge current: 10A
Discharge cut-off voltage: 24 V
Product size: 160 * 75 * 25MM
Charging temperature: 0 ~ 45 ℃
Discharge temperature: - 20 ~ 60 ℃
Battery case: ABS + PC
2. Design scheme of lithium battery for medical equipment:
1) BMS: it is mainly a protection circuit designed for rechargeable lithium battery pack. Due to the chemical characteristics of lithium battery, it is necessary to provide intelligent power calculation, overcharge, over discharge, short circuit, overcurrent and other protection functions to avoid burning, explosion and other hazards.
2) Protection IC (Protection IC): the main protection function chip of the design scheme, which can monitor the overcharge, over discharge, over current, short circuit and other functions of the cell online and constantly, so that the cell can work in a safe, stable and efficient range.
3) Temperature switch: mainly designed for temperature protection function. When the temperature of the battery itself reaches 70 ± 5 ℃ due to other abnormal problems, the temperature switch will act for temperature protection
4) Lithium ion cell: lithium ternary / lithium cobalt oxide.
5) Field effect transistor (MOSFET): MOSFET, in the protection circuit to play a switching role, always make the voltage at both ends of the load will not rise or fall, to ensure voltage stability.
6) Battery package: PBS + PC.