button cell battery cr2025.Technical limitations of lead-acid battery life design

　　Although today's lead-acid batteries have been greatly improved in terms of structural design and raw materials used, and their performance has been greatly improved. Many maintenance-free lead-acid batteries with excellent design and materials have a theoretical life of 15~ More than 20 years, but there are probably very few batteries that can actually reach such a lifespan in use. Take the dry-charge low-maintenance starting lead-acid batteries widely used in cars and motorcycles as an example. The designed service life is more than 4 to 5 years. Through investigation, it is found that few can reach the above level, and most of them last for several months to one year. He died young in 2010. Investigating the reasons, we believe the following are the following:

　　1) The design of the charging equipment is not perfect enough and it is not convenient to use.

　　2) Lead-acid batteries cannot be recharged in time after being discharged, especially over-discharge, which can cause fatal damage to the battery.

　　3) The products of a few manufacturers are of poor quality and are passed off as good.

　　For the above reasons, we believe that 2) and 3) are technically easier to prevent and do well, but 1) involves technical problems that are difficult to solve. Let’s focus on the problems in this area.

　　2 Battery charging technical requirements

　　The technical indicators for guaranteed service life of lead-acid batteries provided by the manufacturer are given when the ambient temperature is 25°C. Since the voltage of a single lead-acid battery drops by about 4mv for every 1°C rise in temperature, a 12V battery consisting of six single cells connected in series has a float charge voltage of 13.5V at 25°C; when the ambient temperature drops to 0 °C, the float charge voltage should be 14.1V; when the ambient temperature rises to 40°C, the float charge voltage should be 13.14V. At the same time, lead-acid batteries also have a characteristic. When the ambient temperature is constant and the charging voltage is 100mv higher than the required voltage, the charging current will increase several times. Therefore, it will cause thermal runaway and overcharge damage of the battery. When the charging voltage is 100mv lower than the required voltage, the battery will be undercharged and the battery will be damaged. In addition, the capacity of lead-acid batteries is also related to temperature. For every 1°C decrease in temperature, the capacity will decrease by 1%. Therefore, manufacturers require users of lead-acid batteries to discharge 50% of the rated capacity in summer and 25% in winter. It should be charged in time.

　　Obviously, lead-acid batteries in daily use cannot be exposed to an environment of 25°C for a long time. There are still morning, noon and night temperature changes in a day, not to mention that there are even greater temperature changes in spring, summer, autumn and winter in a year. Temperature difference, so the various thyristor rectifier types, transformer step-down rectifier types, and general switching power supply type lead-acid battery chargers commonly used on the market currently charge the battery in a constant voltage or constant current mode. It cannot meet the strict technical requirements for recharging lead-acid batteries. Looking at the methods used in the past to charge lead-acid batteries, as well as the lead-acid battery chargers developed based on these methods, it is not difficult to see that the technology is not perfect enough. Using these products to charge lead-acid batteries will inevitably lead to direct charging. Affecting the service life of lead-acid batteries, these chargers also have problems such as narrow operating voltage adaptability range, large size, low efficiency, and poor safety factor.

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