- Discharge characteristics
VRLA batteries are subject to capacity test before leaving the factory. According to YD / t799-1996 standard, the steps of capacity test are as follows:
(1) First, fully charge the tested VRLA battery.
(2) Leave the VRLA battery under test for 1 ~ 24h to make the surface temperature of the battery reach 25 ± 5 ℃.
(3) VRLA battery uses 0.1co current to continuously discharge the load at constant current, and the terminal voltage of VRLA battery is tested regularly during the discharge process; When the terminal voltage of VRLA battery reaches 1.80v, the discharge is terminated, and the final cumulative discharge reaches 100%.
For VRLA battery, the termination of discharge is based on the terminal voltage of VRLA battery, that is, the termination voltage of single VRLA battery is about 1.80v, but the terminal voltage of VRLA battery is closely related to the three polarizations of the positive and negative poles of VRLA battery, and the termination discharge voltage set at 1.80v is determined for the discharge rate of about 0.1c10. Due to the existence of polarization, with the decrease of discharge rate and discharge current, the discharge termination voltage should be higher and higher, otherwise it is very likely to lead to over discharge of VRLA battery. Before, I accidentally browsed an article about batteries. I thought the author explained his knowledge about batteries very clearly. If you are interested in this aspect, please visit tycorun.com。
- Discharge use
When VRLA battery is discharged, attention should be paid to the discharge rate and discharge termination voltage of VRLA battery, especially the setting of discharge rate and discharge termination voltage under different ambient temperatures. Since different ambient temperatures will greatly affect the freezing point of electrolyte and the activity of active substances in VRLA battery, in order to ensure the full chemical reaction, the minimum temperature of VRLA battery should be controlled at about 25 ℃.
The termination voltage of VRLA battery during discharge is set to prevent the voltage and capacity imbalance of each single VRLA battery in the VRLA battery pack during discharge. Generally, the more serious the over discharge is, the harder it will be to recover the backward VRLA battery during the next charging, which will seriously affect the service life of the VRLA battery pack. Generally, the discharge rate of VRLA battery is 0.02c/10, 0.1c/10, 0.2c/10 or 0.3c/10 (C represents the battery capacity, C / 10 represents the discharge rate for 10 hours, and 0.02c/10 represents discharging with 0.02c current for 10 hours). In order to prevent over discharge, not only the discharge rate should be avoided as small as possible, but also the discharge termination voltage must be accurately designed according to the discharge rate and combined with the ambient temperature. Generally, if the discharge rate is 0.01 ~ 0.025c/10, the termination voltage can be set to 2.00v; The discharge rate is 0.25~
At 0.5c/10, it can be set to 1.80v. Due to the existence of concentration polarization, the discharge termination voltage should be lower and lower with the increase of discharge rate and discharge current.
- Discharge requirements
The actual discharge capacity of VRLA battery is related to the discharge current. The greater the discharge current, the lower the efficiency of VRLA battery. For example, when the discharge current of 12V / 24Ah VRLA battery is 0.4C, the time from discharge to termination voltage is 1 hour and 50 minutes, the actual output capacity is 17.6ah, and the efficiency is 73.3%. When the discharge current is 7C, the time from discharge to termination voltage is only 20s, the actual output capacity is 0.93ah, and the efficiency is 3.9%. Therefore, large current discharge should be avoided to improve the efficiency of VRLA battery.
1) Discharge depth
The discharge depth also has a great impact on the service life of VRLA battery. The deeper the discharge depth of VRLA battery, the less the number of cycles. When using VRLA battery, we should not only avoid heavy load overcurrent discharge, but also avoid deep discharge of VRLA battery caused by long-time light load discharge, but also avoid short-circuit discharge of VRLA battery. Otherwise, it will seriously damage the recharging capacity and power storage capacity of VRLA battery and shorten its service life. In the practical application of VRLA battery, we should not first pursue the percentage of discharge capacity, but pay attention to the discovery and treatment of backward VRLA battery, and then do the check discharge experiment after the treatment of backward VRLA battery. This can prevent accidents and prevent the backward VRLA battery from deteriorating into reverse pole VRLA battery.
2) Discharge operation
The purpose of discharge is to check whether the capacity of VRLA battery is normal. Generally, 10 hour discharge rate is adopted. If possible, false load discharge can be used; Considering the convenience of application, the load can also be directly used for discharge. Considering the safety, the discharge depth should be controlled at 30% ~ 50%. Of course, if possible, the discharge can be deeper, which is easier to expose the potential problems of VRLA battery. The voltage of single VRLA battery is detected once every hour. By calculating the discharge capacity of VRLA battery and comparing the voltage value, judge whether the VRLA battery is normal.
The discharge capacity of VRLA battery is calculated as: discharge current (a) x discharge time (H); Under the corresponding discharge capacity, the measured voltage value of single VRLA battery shall be equal to or greater than the corresponding voltage value, that is, the capacity of VRLA battery is normal, on the contrary, the capacity of VRLA battery is insufficient.
Read more: How do silicon solar cells work?