1. Direct charge protection point voltage: Direct charge is also called emergency charge, which belongs to fast charge. Generally, when the battery voltage is low, the battery is charged with high current and relatively high voltage. However, there is a control point, also called protection The point is the value in the above table. When the battery terminal voltage is higher than these protection values during charging, the direct charging should be stopped. The direct charging protection point voltage is generally also the “overcharge protection point” voltage, and the battery terminal voltage cannot be higher than this protection point during charging, otherwise it will cause overcharging and damage the battery.
2. Equalization charge control point voltage: After the direct charge is completed, the battery will generally be left for a period of time by the charge-discharge controller to allow its voltage to drop naturally. When it drops to the “recovery voltage” value, it will enter the equalization charge state. Why design equal charge? That is, after the direct charging is completed, there may be individual batteries “lag behind” (the terminal voltage is relatively low). In order to pull these individual molecules back and make all the battery terminal voltages uniform, it is necessary to match high voltage with moderate voltage. Then charge it for a short while, it can be seen that the so-called equalization charge, that is, “balanced charge”. The equalization charging time should not be too long, usually a few minutes to ten minutes, if the time setting is too long, it will be harmful. For a small system equipped with one or two batteries, equal charging is of little significance. Therefore, street light controllers generally do not have equal charging, but only two stages.
3. Float charge control point voltage: Generally, after the equalization charge is completed, the battery is also left to stand for a period of time, so that the terminal voltage drops naturally, and when it drops to the “maintenance voltage” point, it enters the float charge state. Currently, PWM is used. (both pulse width modulation) method, similar to “trickle charging” (that is, small current charging), charge up a little when the battery voltage is low, and charge up a little when it is low, one by one to prevent the battery temperature from continuing to rise High, which is very good for the battery, because the internal temperature of the battery has a great influence on charging and discharging. In fact, the PWM method is mainly designed to stabilize the battery terminal voltage, and reduce the battery charging current by adjusting the pulse width. This is a very scientific charging management system. Specifically, in the later stage of charging, when the remaining capacity (SOC) of the battery is >80%, the charging current must be reduced to prevent excessive outgassing (oxygen, hydrogen and acid gas) due to overcharging.
4. Termination voltage of over-discharge protection: This is relatively easy to understand. The discharge of the battery cannot be lower than this value, which is the national standard. Although battery manufacturers also have their own protection parameters (enterprise standard or industry standard), they still have to move closer to the national standard in the end. It should be noted that, for the sake of safety, generally 0.3v is artificially added to the over-discharge protection point voltage of the 12V battery as temperature compensation or zero-point drift correction of the control circuit, so that the over-discharge protection point voltage of the 12V battery is: 11.10v, then The over-discharge protection point voltage of the 24V system is 22.20V.