Knowledge of electric vehicle batteries from several major errors A
Electric car charging lead-acid batteries, there are several key parameters: the maximum charging voltage, float voltage, float switch current, maximum charge current. They should be how much? How to develop? Foremost among which is the maximum charge voltage, and how many for the better? And analysis of gas, filled capacity and ambient temperature, what is the relationship? As everyone on this vary, the requirements of the battery manufacturers are not the same. The maximum relative error of charging voltage range? We can not be divorced from the real work object, the blind development of surplus conventional precision. We have received notification of a service department of electric vehicles: battery charger with a voltage higher than 0.1V, the battery charge and therefore the expansion of the thermal runaway; also been informed that: set lower than the required voltage is 0.1V, the battery charge less, early retirement. The error of a few thousandths of causing such serious consequences, really miss is his fear of a thousand miles away, lead-acid batteries do indeed have such a mystery? In order to solve the problems of the electric vehicle charging mystery, do the following experiment.
With a sink full of water, the battery on the water, above the battery has a collection of gas used upside down funnel, funnel top of the gas volume can be measured with the syringe. Charged with the adjustable power supply, with two digital multimeter to measure the four half-charge current and charge voltage.
Test time is in winter, the water temperature 5 ℃. Conditions 2A is unified with the current charge, the charging voltage were used to 43V, 44V, 45V round of the loop in turn, float convert all current 400mA, the charging time of each record, including the late charge current drops with time points of data, started gassing voltage, gas analysis by time records. After charging the battery, with the precision of the very few records of discharge capacity of the power station. Charge into the battery is read out on paper in the calculation of the time between the current curve and the coordinates of the area (capacitance charging current of time is the definite integral.) Data in the table below:
Experimental data obtained, the most surprised is: how much power is almost filled with the charging voltage. Many people think that the low battery charge voltage will charge less, the battery will be scrapped ahead of salinization, especially in winter when low temperatures. But this test is just in the winter, the water temperature is only 5 ℃, the center of test voltage is 44V, the upper and lower bias 1V, the relative error is 2.3%. Charging with 43V and 45V in the case of electricity and emit electricity filled almost the same, and vary widely recognized by the test is to use the same set of batteries, the same charge and discharge conditions, in their turn to do the same test, the experimental data duplication same law, causal factors can be ruled out interference test data is accurate and credible. Principles from the battery point of view, as long as the charging source voltage higher than the battery terminal voltage will charge the battery until the battery active material in the conversion is complete. The maximum charge voltage, that is, by the constant current charging power supply began to shift to the constant pressure zone area, this shift is filled into the electricity from the battery itself how much reflects the number of active substances decisions, charging voltage level, is only capable of electrochemical reaction conditions, as long as the open circuit voltage than the battery will recharge the battery, the number of substances involved in the reaction can be determined by the battery itself. From this idea of understanding, is not rare that the charging voltage level has little effect on the battery capacity.
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