Lithium-ion battery for portable medical equipment for energy advantage

An energy density higher technology frees more than other similar products more energy, and smaller.

Consumer electronics, and many other industries are becoming more and more sophisticated products, mobility and medical appliance manufacturers are no exception to this trend raises the on-site rescue equipment, control equipment and fixed the performance of the medical equipment, thereby promoting the development of the healthcare industry. But in addition to medical device manufacturers increased portability of course want to be able to produce reliable instruments, because people's lives often hangs a line. Mobile phone is broken is annoying, but if portable cardiac monitor or infusion pump because the batteries run out and stop running, end users — and patients — problems are much more serious. A few years ago, medical professionals will salvage failed life equipment to the site; for then portable apparatus of technology is not yet mature. But now, a large number of monitoring instruments, ultrasonic equipment and infusion pump can be away from the hospital establishments use — even the battlefield. Portable device for mobile and more convenient. It is precisely because such as lithium-ion battery technology application, up to 50 pounds of heavy defibrillator can be more portable, more compact user friendly device replacement, would not have caused health care personnel strained muscles. Patient mobility is becoming increasingly important. Today, the patient may be transferred from the Department of Radiology to the intensive care unit, from the ambulance to the emergency room, or ambulance from one hospital to another hospital. Similarly, portable home instrument and the popularity of mobile monitoring equipment so that patients can stay in love, and not necessarily to stay at medical institutions. Portable medical devices must achieve full sense of the portable, provide the best service to patients. On smaller, more portable medical equipment needs and therefore significantly increase greatly inspired people on higher energy density, more compact battery pack. Laptop and mobile phone use lithium-ion battery technology has many breakthrough medical device design engineers can take advantage of this innovation. Compared with other traditional technologies, lithium-ion batteries in portable medical device applications with many advantages. This includes higher energy density, lighter weight, the cycle of life is longer, battery capacity to maintain better performance, as well as for a wider range of temperature. Because of the chemical properties of unique, lithium-ion technology to design constraints and previous battery technology such as nickel-hydrogen compounds (NiMH), nickel cadmium (NiCd) and sealed lead acid (SLA). At the same time, the medical equipment in some aspects than consumer electronics products have more stringent operating requirements; due to reliability is important, therefore, need to have a powerful battery pack with a precise power monitoring and reliable battery. This article in conjunction with the medical device requirements and characteristics of lithium ion technology, provides an overview of the portable power system design considerations. And compares the lithium ion battery and other chemical characteristics and capacity of the battery. Energy density and voltage of Figure 1. Energy density of lithium ions are far higher than nickel compounds. Lithium-ion battery technology's main advantages is its energy density is dramatically improved. The same size and weight, the lithium ion battery can store and release of energy more than other rechargeable batteries. Energy density of the volume and quality measurement in two ways. Lithium-ion technology is available near the volume 500Wh/L energy density and 200Wh/kg of weight energy density (see Figure 1). Compared with other technologies, lithium-ion can release more energy, but also smaller and lighter weight. Lithium-ion battery voltage more than other rechargeable batteries, usually about 3.7V, NiCd or NiMH batteries for 1.2V. This means that you need to use multiple sections of other batteries, only the desired section of the lithium ion battery can meet use requirement. Portable instrument design using battery energy density, the higher the volume of its products, portability is also better. Battery pack volume of bridging means that engineers can take advantage of the extra space, in the same product to add more new features (see Figure 2). Self-discharge figure 2. Cylindrical lithium-ion batteries and prismatic two shapes that can be made into different dimensions and capacity of the battery. Rechargeable battery capacity will keep losses. This phenomenon is known as self discharge. But if stored properly, the loss of most of the capacity is still recoverable. All batteries should be at room temperature (25 ° C or lower) of storage to keep maximum battery capacity. End user shall SLA battery placed in the low temperature storage, and as far as possible each time charge capacity close to 100% of their capacity to maintain optimal performance. Sealed lead battery at 25 ° c with place for 6 months after discharge capacity of approximately 20%; but the 40 ° C to place six months after the value is increased to about 30%. NiMH batteries are also similar recommendations should be followed to avoid long-term storage of the reactants. NiCd and NiMH batteries at 25 ° c with placement of 1 month, the self-discharge rate of about 20%, then the self-discharge rate of growth has slowed significantly. Conversely, when the lithium-ion battery charging power when storage is 30-50%, you can get the best cycle life. Lithium-ion battery 25 ° C storage 6 months after the self-discharge capacity of only 10%. Rate characteristics when selecting material, consideration should be given to the terminal device of inrush current and maximum discharge rate. Battery or battery pack to high voltage discharge may cause degradation. If the design is not considered in this context, the terminal device may close due to lack of voltage. The high percentage of NiCd battery for continuous discharge rate can reach 2C (battery, nominal capacity of two times) or even higher, depending on the battery raw materials and internal impedance. Many of the SLA battery of continuous discharge rate can reach 3C or even higher. Most lithium-ion battery for continuous discharge rate was only 1C, but using the technology of the new battery, its continuous discharge rate is extremely high, reached a 30-second 80A, sustainable, and NiCd and SLA battery competition has great advantages. Cycle life battery cycle life is the battery capacity drops to its original capacity of a certain percentage of the battery charge and discharge cycles. Lead-acid battery life cycle of about 250-500, depending on the manufacturer's product quality and depth of discharge (discharge capacity up to the rated capacity of60%). NiCd, NiMH and Li-ion batteries can usually be tolerated 500-700 time charge-discharge cycle, its capacity is reduced to 80% of the rated capacity. No matter what chemicals, batteries discharge depth deeper, users can use the fewer number of cycles. Differences in charging lithium-ion battery charging different than other batteries. SLA battery charging, is preferred and constant rate usually rated capacity of 1/10 (C/10), charging time is 14-16 hours, or trickle charging or floating charge, charge rate for C/C/20-30. NiCd battery for termination of the recommended way of V-△, charger voltage peak. NiMH batteries because of its characteristics of fever, charging process requires use of temperature detection, Δ Δ T/t to its preferred form. Specially designed for the fast charge NiCd and NiMH batteries-available at C/2-C/3 under charging a rate of 4-6 hours. Very low damping nickel batteries as a fast charge battery that can charge in 1C rate for 1 hour. Finally, lithium-ion batteries recommended constant current/voltage charging (CC/CV). Typically, lithium-ion battery-powered devices to rate charging 1C 60-75 minutes to 4.1V, from the original low-energy state reached capacity 80-90% of the State. Other batteries, in addition to the use of high-current charge special battery, the same charge to 80-90% of the time may take more time. Lithium ion batteries also slow filling of 4-5 hours to get the remaining 4.2V, 10-20% of power. This charging method has two advantages. Users can in a very short period of time to get close to full charging and power, and charge completion of actual voltage does not exceed 4.2V. It should be noted that: If only the lithium-ion battery charger to 4.2V 4.1V instead, you can extend its life cycle; but each of the available capacity will be reduced. In some medical devices in the battery is a kind of back-up device, it stays charged state, to ensure that the readily available. Lithium-ion chemistry determines its not appropriate for trickle charging; lithium-ion battery cannot be recharged using constant float. But there are several ways you can not damage the battery or impact on the basis of medical devices, reduce the excessive charging lithium-ion battery. One way is to trigger the battery before charging again to ensure that the battery discharge capacity is at least 20%, followed by standard charge. Lithium-ion technology and SLA compared to significantly increase energy density, in most cases sufficient to prevent the lithium ion battery is fully charged. Safety circuit diagram 3. Lithium-ion battery pack design needs to adopt electronic safety devices. Battery pack also contains power monitoring unit and charging circuit. Each battery technology has its set of security concerns. NiCd battery pack with a current breaking device to prevent the occurrence of serious fault, this is excellent battery design essential. NiMH with fever of chemical properties, so the batteries need equipped with heat-sensing device, charger, charging excessive, battery pack itself also with current breaking devices. In lithium-ion battery pack, in the event of excess voltage, i.e. lithium metal production. This shows the battery should use safety circuit, so that the charging and discharging the battery voltage during the stay in a specific range (see Figure 3). Although the SLA battery typically does not require external security components, but many medical device manufacturers still insist on will not be reset fuse into battery inside or around. As most of the SLA battery with positive and negative plates of, if not fuse, when placed on a metal plate, it is easy to have a short but massive metal plate exists in healthcare facilities. These batteries are also possible other danger of short circuit. If you have a short, units that have a potential explosion. Lithium-ion battery pack less danger of short circuit, the safety circuit is used primarily to protect the battery. The battery in the safety circuit increases the equipment cost, cost more space. Designers must be aware that these are the batteries of the selection process will take into account in weighing the factors. Overall, despite the existence of a safety circuit, lithium-ion battery will still be able to narrow the battery pack size, reducing its weight, and to release more energy. Power monitoring to more medical device manufacturers began to use lithium-ion technology, battery management features in the industry has become increasingly common. Power monitoring devices for end users to provide certain information, such as the battery is expected to use time, etc. Management of the introduction to a large extent on the battery charge evaluation and the implementation of the programme. The battery management, use lithium-ion battery designers a wide selection of programmes. For example, some lithium-ion battery monitoring device contains information feature, you can report has been in charge-discharge cycle times. This type of information in a number of important medical equipment has an important role in. Power monitoring there are two basic methods: count based on voltage and Coulomb. The two technology solutions, their accuracy as high as 99%. -Temperature resistance lithium-ion battery at 40 °-45 ° C in high temperature conditions, performance is better than other batteries. SLA and NiMH batteries in high heat environments does not work. This becomes its first aid tools use a limiting factor, because at this point, users cannot save their portable devices in low-temperature environment. Conclusions in choosing the best equipment for portable power options, you must total cost and overall performance assessments. Lithium-ion technology for high-voltage characteristics can reduce battery usage, thereby reducing the cost of the battery pack to use nickel technology battery approximately equal. In addition, lithium-ion battery supplier constantly using new materials, to reduce the cost of the battery. Lithium-ion battery of small volume, light weight, high energy, recycling, long service life and durability, heat resistance, high voltage and good characteristics make it a potential advantage. Medical electronic product manufacturers can take advantage of these properties, expand the product market, and finally to consumers, healthcare professionals and patients in treatment, and other benefits.