What are the reasons for the sulfation of the negative plate of the battery

by:Power Kingdom     2021-07-09

   If the battery cannot be charged after a few months of use, the cause is that the negative plate of the battery is sulfated on the one hand. This is because ordinary constant voltage chargers may cause incomplete charging due to design settings (yes Use a charger that does not meet the requirements, such as the charging voltage is too low or the current is too small), even if it can be charged or discharged during use, the capacity will gradually decrease due to insufficient charging and the life will be shortened. On the other hand, there is no control of the voltage limit setting when discharging and using, which causes the battery to work overload, causing frequent over-discharge and shortening the battery life; on the other hand, due to bad usage habits, such as the battery is often not charged immediately after use , But wait for the next time to use before charging. This poor use method will shorten the battery life

   There are three main reasons for the sulfation of the negative plate of the battery:


  ①Overdischarge: Constant current or constant power discharge below the battery's specified lower limit voltage is called overdischarge. For example: 12V35AH uses 3.5A to discharge to 10.8V, it should be stopped, if the discharge continues, it is overdischarge; in addition, the quality of the equipment or controller is disconnected, but there is current leakage, and it is still discharged at a small current, which is also an overdischarge.

  ②Undercharge: The battery runs for a long time without being fully charged, which is called undercharge. For example: after the battery is discharged, charge it, if it is not enough, discharge it again.

  ③Failed to recharge in time: the battery is discharged and not charged in time. For example, if the battery is discharged and ignored, it means that the battery has not been replenished in time.

   The above three conditions can cause the sulfation of the negative plate of the battery, which is manifested in the formation of a dense white lead sulfate crystal on the negative plate, which has poor electrical conductivity. It does not participate in the battery chemical reaction and is generated on the surface of the negative plate, which also affects the reaction and utilization of other active materials. It will cause the internal resistance of the battery to increase and the capacity to decrease. According to Ohm's law, when the voltage remains the same, the resistance increases and the current decreases. As a result, the battery is sulfated, and ordinary constant voltage chargers may not be charged, even if they can be charged or discharged, the capacity will be reduced and the life will be shortened.

   The degree of battery sulfation depends on the degree of over-discharge, under-charge or failure to recharge in time, see below:

  1. The level of over-discharge voltage, the size of current, the number of times, the lower the over-discharge voltage, the smaller the over-discharge current, the more the over-discharge times, the higher the degree of sulfation.

  2, the level of undercharge voltage, the magnitude of current, the number of times, the lower the undercharge voltage, the smaller the undercharge current, the more the undercharge times, and the sulfation The degree is higher.

  3. The length and frequency of the shelving time for not replenishing electricity in time, the longer the shelving time, the more shelving times, the higher the degree of sulfation.

  2) Correction method:

   It is possible to recover the sulphated battery, but the slightly sulphated battery is OK Complete recovery, including capacity recovery and function recovery, recovery method: use small current for multiple charging and discharging cycles. For example, for a 12V12AH battery, use 1.2A constant current to charge for 12H, and 0.6A constant current to discharge to 10.8V, repeat 4 times, the battery can be recovered.

The degree of sulphation is relatively high, and the capacity can only be partially restored, which can be restored to 40%-100% of the initial capacity, depending on the degree of sulphation.

   is severely sulfated, the capacity cannot be recovered, and the battery fails, because the sulfation of the negative plate is one of the battery failure modes.

  3) Preventive measures:

   Correct use of the battery, and try to avoid 'overdischarge and undercharge' and ' The electricity was not replenished in time'.

  1. The discharge equipment used must have termination (lower limit voltage) protection. Set according to the discharge current, such as 12V12AH, discharge current below 0.2C, the lower limit voltage is set to 10.8V; 0.2-0.5C current discharge, the lower limit voltage is set to 10.5V; 0.5-1C current discharge, the lower limit voltage is set to 10.2V ; Current discharge above 1C, the lower limit voltage is set to 9.6V.

  2. After the power is discharged, please do not store or shelve it, and recharge it immediately.

  3. Please use it after fully charged.

  4. Even if the battery is not in use, it needs to be fully charged before putting it aside.

   5. Because the battery is installed on the equipment, it is affected by the equipment structure and wiring, there must be more or less current leakage (as little as a few milliamperes, as many as Ten milliamps), so the power supply circuit should be disconnected (not only to disconnect the electronic switch) when the equipment is stored for a long time (exceeding).


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