一.Phenomena and causes of reverse polarity of Lead-acid Battery
The reverse polarity of the lead-acid battery refers to the change in the positive and negative poles of the battery. The reverse polarity phenomenon is reflected in two aspects. Reversed. In this case, when the lead-acid battery is filled with acid and the terminal voltage is measured with a voltmeter, the terminal voltage value is less than the sum of the rated voltages of the individual batteries, or the terminal voltage is negative.
On the other hand, lead-acid batteries are used in multiple series during capacity discharge, because a certain storage battery (or a certain single storage battery) has a low capacity or completely loses its capacity. During discharging, this battery is quickly discharged and is reverse-charged by other batteries, so that the original negative electrode becomes the positive electrode, and the original positive electrode becomes the negative electrode, and the terminal voltage appears negative.
For the former reverse polarity fault, when measuring the battery terminal voltage (a battery composed of multiple single cells), it can be found that if there is a reverse polarity of a single battery, not only the 2 V voltage of the battery will be lost, but also the increase 2 V reverse voltage, the terminal voltage should be reduced by about 4V.
For example, for a battery with a rated voltage of 12 V, if the terminal voltage is measured to be about 8 V, it means that there is a single cell battery with reverse polarity. If the terminal voltage is about 4 V, it means there are 2 single-cell reverse poles. If the terminal voltage is about -4 V, it means there are 4 single-cell reverse poles. If the terminal voltage is -12 V, it means there are 6 single cells. The grids are all reversed.
For the latter type of reverse polarity fault, the terminal voltage value (negative value) varies with the discharge situation. Generally, during the detection, the battery should be removed from the discharge circuit in time for this situation to avoid damage to the battery.
二.Short circuit phenomenon and cause
The short circuit of a lead-acid battery refers to the connection between the positive and negative electrodes of the lead-acid battery. The short-circuit phenomenon of lead-acid batteries is mainly manifested in the following aspects:
(1)The open circuit voltage is low, and the closed circuit voltage (discharge) quickly reaches the end voltage.
(2)When a large current is discharged, the terminal voltage quickly drops to zero.
(3)When the circuit is open, the electrolyte density is very low, and the electrolyte will freeze in a low temperature environment.
(4)When charging, the voltage rises very slowly and always stays low (sometimes it drops to zero).
(5)When charging, the temperature of the electrolyte rises very quickly.
(6)When charging, the electrolyte density rises slowly or hardly changes.
(7)No bubbles or gas appear late when charging.
The main reasons for the internal short circuit of lead-acid batteries are as follows:
(1)The quality of the separator is poor or defective, allowing the active material of the electrode plate to pass through, resulting in virtual or direct contact between the positive and negative plates.
(2)The displacement of the separator causes the positive and negative plates to be connected.
(3)The active material on the electrode plate swells and falls off. Due to the excessive deposition of the fallen active material, the lower edges or side edges of the positive and negative plates are in contact with the deposits and the positive and negative plates are connected.
(4)Conductive objects falling into the battery cause the positive and negative plates to connect.
(5)The “lead flow” formed during the welding of the electrode group is not exhausted, or there are “lead beans” existing between the positive and negative plates during assembly, and the separator is damaged during the charging and discharging process and the positive and negative plates are connected.
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