Introduction to the selection and use of backup batteries

When designing clock power supplies or backup power supplies, many customers encounter problems such as battery clock reset, inability to charge, insufficient backup time, etc. due to the selection of power management solutions. The following will specifically talk about how to choose a backup battery and how to use it.

When choosing a power supply solution, you must first consider the purpose and environment of your battery use. For design engineers, the purpose of use is very clear, but the battery use environment is often not very clear. They often ask battery operators whether the other party's battery is suitable for their own functions without any opinion. From the perspective of battery operators, each battery operator will design one or several battery solutions for customers based on customer needs and explain how to do it. In fact, there is a component of action in this process.

Batteries have different functions due to different systems. Although many people say that one battery can be used as another battery, it is not the case. The following will introduce the best application concepts of the following types of batteries:

1. Rechargeable micro lithium-ion batteries. This type of battery currently mainly includes MC, ML, MS and other series. The working voltage is 0~3.3V. Due to its small size, it can be used in devices such as mobile phones, MP3, SMART NOTEBOOK, voice recorders, laptops, PDAs, PDA phones, etc. that need to maintain clocks or RAM data. Generally speaking, the diameter of this type of battery is 4~6 mm, the thickness is 1.2~2.1 mm, and the capacity is 0.4~5 mAh. In addition to its small size, this type of battery generally has a very long service life during shallow charging and discharging. Basically, the capacity of ML and MS is higher than that of MC, but MC has better stability and can be restored to life by charging after being short-circuited.

2. Rechargeable button-type nickel-metal hydride batteries. This type of battery is different from traditional cylindrical batteries and square batteries. Its pole pieces are generally directly pressed, and then the positive and negative electrodes are wrapped with conductive materials. Due to the structure, the internal resistance of this type of battery is 4 to 6 times larger than that of traditional nickel-metal hydride batteries, and it cannot withstand large current charging and discharging; the advantage is that the self-discharge performance and overcharge resistance are much better than traditional batteries. The capacity of this type of battery ranges from 20 mAh to 600 mAh, and there is no limit on the specified current charging time. At the same time, the charging process does not require any protection and voltage limit, and the charging circuit is much simpler. It can be seen that this type of battery is suitable for single-chip microcomputer circuit boards, such as fuel dispenser control boards, textile equipment circuit boards, and environmental protection equipment lines. Road panels, car alarms, cordless telephone equipment, tax control machines, handheld POS, Bluetooth headsets, etc. require batteries with low current power supply, and can also serve as backup batteries to ensure normal operation of the equipment when the external circuit is out of power. At this time, although many companies also choose to use traditional batteries, they can be used on the surface, but in fact the batteries are not suitable in terms of charging and self-discharge, life, spatial structure, weight, etc. Traditional batteries use a winding structure, with small internal resistance and large self-discharge, so they can meet the charging and discharging requirements of larger currents. If charged and discharged with a small current, the battery can be used for one or even two years, but due to the long-term small current, the active material inside the electrode is not activated enough, which can easily lead to battery passivation, and ultimately lead to battery capacity loss or even failure.

[page]3. Disposable lithium manganese batteries. The most commonly used batteries of this type are CR2032 and others. In terms of performance, there are big differences between domestic lithium manganese batteries and foreign ones, mainly in terms of stability, leakage, lifespan, etc. Of course, if you use single lithium manganese batteries and do not need any pins, domestic ones will have a great advantage in price. If you need to use pins, please choose foreign brands, especially German Varta batteries. Although there is no price advantage, you will definitely get a higher return in terms of quality assurance. The main reason is that this type of battery requires very strict equipment when welding pins. Electric welding pins will cause the battery surface to instantly heat up to 1000 degrees or even higher, and domestic batteries can easily At this high temperature, the active materials inside the battery are burnt, causing internal damage to the battery; at the same time, lithium is a very ductile material, and spot welding will cause the lithium inside the battery to expand and penetrate the diaphragm to short-circuit. Although these phenomena do not appear to be a problem in appearance, and the operator will explain that there is no problem, the problem is actually very obvious. Usually, the capacity of CR2032 is 230~260 mAh, and the service life can reach 6~10 years under the specified current conditions, while domestically produced batteries may have problems after 1 year. This type of battery is mainly used for equipment that requires a small current as a backup power supply and can be directly replaced by customers without causing product quality disputes. Such as computer motherboards, calculator motherboards, fax machine motherboards, etc.

4. Rechargeable micro lithium polymer battery. This type of battery is increasingly used in micro MP3, wireless headphones, etc. However, due to the immaturity of the industry, users of this type of product have more or less already or will face quality complaints due to battery quality issues. Lithium polymer battery is undoubtedly a new type of battery with great development potential, but in fact, in terms of large body and small size, no battery company's products have passed the test, especially in terms of high temperature performance, low temperature performance and anti-expansion performance. Otherwise, why don't SONY and SANYO have products? If you must choose this type of battery, please pay attention to the following aspects: first, do not pursue batteries with a high volume capacity ratio; second, do not use tight assembly; third, the charging protection and discharge protection of the protection circuit must use advanced ICs instead of those made in Taiwan; fourth, make sure that the product will not be used in an environment with a high temperature of more than 60 degrees; fifth, the usage time should not be designed to exceed 70% of the time the battery can withstand.