1 Introduction
Although today's lead-acid batteries have been greatly improved in terms of structural design and use of raw materials, the performance has been greatly improved. The theoretical life expectancy of many design and well-preserved maintenance-free lead-acid batteries is 15~. For more than 20 years, there are very few batteries that can really achieve such a long life in use. For the lead-acid battery with dry charge and low maintenance for automobile and motorcycle, the design service life is 4 to 5 years. According to the investigation, it is rare to reach the above level, most of the months to one. Years have died, and the reasons for this are as follows:
1) The design of the charging device is not perfect and it is not convenient to use.
2) The lead-acid battery cannot be recharged in time after being discharged.
In particular, overdischarge can cause fatal injuries to the battery.
3) The quality of the products of a few manufacturers is inferior and shoddy.
For the above reasons, we believe that 2) and 3) are technically easier to prevent and do. Only 1) involves technical problems that are difficult to solve. The following focuses on the problems in this area.
2 battery charging technical requirements
The technical specifications for the lead life of the lead-acid battery provided by the manufacturer are given at an ambient temperature of 25 °C. Since the voltage of the single-acid lead-acid battery has a characteristic of a temperature drop of about 4 mV per 1 ° C rise, a 12 V battery consisting of 6 single cells connected in series has a float voltage of 13.5 V at 25 ° C; when the ambient temperature drops to 0. At °C, the float voltage should be 14.1V; when the ambient temperature rises to 40 °C, the float voltage should be 13.14V. At the same time, the lead-acid battery has a characteristic. When the ambient temperature is constant, the charging voltage is 100mv higher than the required voltage, and the charging current will increase several times. Therefore, the battery will be out of control and overcharged. 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 the lead-acid battery is also related to the temperature. The capacity will decrease by 1% for every 1 °C decrease in temperature. Therefore, the manufacturer requires the user of the lead-acid battery to release 25% of the rated capacity in the summer and 25% after the release in the winter. It should be charged in time.
Obviously, the lead-acid battery in daily use cannot be in the environment of 25 °C for a long time. There are still early, middle and late temperature differences in the day, not to mention the four seasons of spring, summer, autumn and winter. Temperature difference, so the current various types of thyristor rectification type, transformer step-down rectification type, and general switching regulator power supply type lead-acid battery charger, which are commonly used in the market, charge the battery in constant voltage or constant current mode. It is impossible to meet the stringent technical requirements that need to be met for the supplementary charging of lead-acid batteries. Looking at the methods used to charge lead-acid batteries in the past, and the lead-acid battery chargers developed according to these methods, it is not difficult to see that the technology is not perfect enough to charge lead-acid batteries with these products. Affect the service life of lead-acid batteries, and these chargers also have problems such as narrow working range, large volume, low efficiency, and poor safety factor.
Figure 1 is a schematic diagram of the principle of natural balance charging
3 natural balance charger
In response to the general problems of charging the above lead-acid batteries, Changsha Yuheng Electronics Co., Ltd. conducted a long-term in-depth study on lead-acid battery chargers, and produced new charger series products with its unique method and ingenious design. It solves the complicated technical problems in the charging of lead-acid batteries. It has been proved by many years of experiments that the service life of lead-acid batteries has been greatly improved. (This technology has been patented)
Now briefly introduce the new method of battery charging - natural balance charging method. What is the natural balance method for charging the battery? Please refer to the connection diagram of the battery charging shown in Figure 1.
In Figure 1, there are two power supplies EA, EB. When the power supply EA and the power supply EB are at the same ambient temperature, the positive pole and the positive pole are connected, and the negative pole is connected to the negative pole. In the closed circuit formed by them, the following relationship exists. If the EA is higher than the EB, the EA will supply the EB with the voltage of EA-EB=ΔE, and at the same time, it will provide a Δi current to the power EB for circulation and perfusion according to the magnitude of ΔE. When the EB absorbs the Δi current provided by the EA, the EB rises. When it is completely equal to EA (in the battery, the rise of the battery terminal voltage and the increase in the amount of charge storage), the power supply EA will stop supplying current to the power supply EB, that is, EA=EB, ΔE=0, Δi=0.
In the above description, we replaced the EB with a charged battery and calculated the voltage corresponding to the battery at different depths of discharge and ambient temperature. The EA is carefully designed to be connected to the power supply with the output voltage and current automatically adjusted according to the battery charge balance at different ambient temperatures. In the fully idealized case, the power supply EA can charge the battery according to the current that the battery can accept at any ambient temperature. After the battery is fully charged, ΔE=0, Δi=0, the EA power supply will no longer consume power. EA only provides tracking balance compensation for the charged battery with the change of ambient temperature. Since the whole process of battery charging is completely automatic, we call it the natural balance method.
The fully idealized situation of this method is: after the battery is fully charged, the voltage difference ΔE=0 between the EA and the charged battery EB, naturally Δi=0, since the EA has no power supply battery (EB), the battery It is impossible for the electrolyte to boil, and it is impossible to decompose the water in the electrolyte in the battery, and it is even less likely to increase the pressure and temperature in the battery, posing a safety hazard. Therefore, the method is provided to the battery, which is neither convenient for charging the battery nor for charging the battery, but is more convenient, safer and more reliable.
From the above analysis, it is not difficult to see that this method is especially suitable for maintenance-free charging of maintenance-free and less-maintained lead-acid batteries, and is more suitable for daily maintenance and charging of batteries used for intermittent discharge, which is beneficial to improve the daily use of the battery. Reliability, improve battery life.
Finally, the main technical indicators of a smart charger for motorcycle 12V lead-acid battery developed by the natural balance charging method are introduced:
1) rechargeable battery 12V4 ~ 10Ah;
2) Adapt to the input power supply for AC 100 ~ 240V, DC 120 ~ 370V;
3) weight ≤ 100g; volume 60mm × 35mm × 30mm;
4) Applicable ambient temperature -10 ~ 45 °C.
4 Conclusion
There are two reasons for affecting the service life of lead-acid batteries:
1) Lead-acid batteries have stringent requirements on their charging equipment when the ambient temperature changes. Due to the design defects of the past charging equipment, it affects the normal service life of the battery.
2) After the discharge of the lead-acid battery, due to the inconvenient use of the charging device in the past, the user cannot recharge the battery in time, and the damage caused by the battery is greatly shortened.
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