How does the AGM battery charge?

The AGM battery must use a dedicated AGM battery charging device, and the FMC-2420 AGM smart charger can be selected. The way to use the charger: Turn on the charger power button -- press the AGM charger switch -- and then charge.

The method of using charger as follow:

1. Turn on the charger power button.

2. Press the AGM charger switch.

3. Then charge.

Determine the rated voltage and rated capacity of the battery or battery pack. The rated voltage is used to determine the charging voltage and the rated capacity is used to determine the charging current.

About voltage: The easiest way is to read it from the tag; for example, the rated voltage of the CSB battery is 12V.

If the label is worn or not at all, it can be judged from the number of vent holes or safety valves that are round holes at the top of the battery that can be opened or opened. To be sure, all lead-acid batteries currently have venting holes. Each vent represents one unit, 2V, so the total voltage of the battery shown in the other figure is 24V because it has 12 vents.

About the capacity: can also be read from the label or calculated; in general, the label will indicate the rated voltage of the battery, as shown in Figure 3 PNP battery is marked as 65Ah, but the UPS battery is usually represented by W, as shown One shows 34W. For this kind of battery, the simple calculation method is the wattage divided by four, that is, 8.5Ah; but when it can only be estimated according to the volume or importance. And the error is large. Generally speaking, the 12V100Ah AGM battery weighs 30~35kg, therefore, if the battery weighs 500kg, it can be calculated that its capacity is about 700Ah.

If you only need to charge the battery once using the method described in this article, this step can be skipped; if you need to use it for a long time, it is recommended to perform this step carefully to determine the open circuit voltage when the battery is 100% fully charged. The industry term is 100%, OCV (open circuit voltage) at SOC (stage of charge).

There are several ways to know the value:

First, use a DC voltmeter to measure the voltage of the battery that has been fully charged for more than one hour after being fully charged, and is directly obtained;

Second, get from the file; the value will not be printed on the battery label, but usually can be obtained from the manufacturer's operating instructions or MSDS;

Third, for a flooded battery, it can also be obtained by testing the density of the electrolyte of the battery when fully charged; the method is OCV=SG+0.84, for example, the density of the electrolyte is 1.35 g/ML, and the open circuit voltage of the battery is OCV. =1.35+0.84=2.19V, as shown in the figure below.

It is important to obtain the voltage when the battery is fully charged. It can be used to verify that the battery is fully charged, to determine the battery charge or the depth of discharge.

Determine the charging voltage.

The charging voltage is divided into a floating charging voltage, a uniform charging voltage, a fast charging voltage, and the like. Generally speaking, the floating charging voltage is used for daily floating charging, and the lowest is used; the charging is used for recharging after discharging, and is higher; the fast charging is a voltage that is rapidly fully charged under the emergency scene, and the highest is not commonly used.

The charging voltage referred to herein is the average charging voltage.

Some batteries will be labeled with charging voltage, which can be divided into floating charge and average charge. For example, the floating charge voltage is 13.5v ~ 13.8v, and the average charging voltage is 14.4v ~ 15.0v. This is relatively simple, the direct use of charging voltage can be charged, can choose a relatively safe middle value or minimum value. The highest value of average charging pressure can be considered as quick charging pressure, which is generally considered to be harmful to the battery.

If the charging voltage is not indicated on the battery, the reasonable average charging voltage can be estimated according to the open circuit voltage OCV when the battery is fully charged. Generally speaking, the open circuit voltage of the 12V battery when fully charged plus 1~1.5V is a reasonable average charging voltage. Other rated voltage batteries and so on.

If you do not know the open circuit voltage when the battery is fully charged, you can occasionally blindly charge with 2.4VPC voltage, but it is more difficult to judge when the battery is full, there may be overcharge, causing certain damage to the battery. The so-called 2.4VPC, that is, 2.4V / cell, 2.4V per unit, if it is 12 units, the average charging voltage can be 28.8V

Determine the charging current.

The charging current is related to the rated capacity of the battery. It is generally 0.1C~0.4C, which is one tenth to four tenth of the rated capacity.

If it is a 100Ah battery, it is 10A~40A. It can be measured with a DC ammeter, a clamp meter.

Of course, some of the most advanced manufacturers on the market today use thin plate technology, which has increased the charging current to 1C, which is equal to the rated capacity. This high-current charging method will greatly shorten the charging time, but this type of high-end battery is not popular enough. The commonly used 0.1C~0.4C method is still used in this paper.

Wiring is very easy, the positive pole of the charger is connected to the positive pole of the battery, the negative pole of the charger is connected to the negative pole of the battery, and then the charger and the power supply are connected, and finally the charger is started for charging.

It is worth mentioning that for multi-cell battery charging methods, I recommend parallel charging. Because parallel charging can improve the consistency of the battery, and low-voltage charging is also safer.

It should be noted that when charging in parallel, the wiring should adopt the diagonal method to improve the consistency of the current shunt. The so-called diagonal connection method is as follows.

Determine the charging time, or when to stop charging.

If it is not blind charging or charging with an excessive voltage, the charging current is reduced as charging progresses.

If the charging is performed at the recommended charging voltage of the manufacturer, in general, the charging current can be considered to be fully charged when it is reduced to 0.03C. For example, a 100Ah battery, if using the voltage recommended by the manufacturer, is considered to be substantially fully charged when the charging current is less than 3A.

Alternatively, the time required to charge 1.2 times the required amount of power is the charging time. For example, a 100Ah battery, fully discharged, needs to be charged 100Ah to be full; 1.2 times 120Ah; if the charging current is 0.15C or 15A, then 120÷15=8 hours can be almost fully charged.

Determine if it is full.

This can be done if necessary. The method is, after the charging is completed, disconnect all the lines, leave it for more than one hour, and then measure the battery voltage. It can be compared with the standard curve to determine if it is full.

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