TW201405999A - Charging device with battery management system for rechargeable battery - Google Patents

Abstract

A charging device with battery management system which remains a rechargeable battery in full capacity during standby after being fully charged is disclosed. The charging device includes a charging module, electrically connected to a power source, for charging the rechargeable battery; a voltage detecting module, for detecting a voltage of the rechargeable battery; and a determination module, for instructing the charging module to charge the rechargeable battery with a supplementary current when the voltage of the rechargeable battery detected by the voltage detecting module reduces to a first predetermined voltage until the voltage of the rechargeable battery reaches a second predetermined voltage. Reduce of the voltage of the rechargeable battery is due to self-discharge of the rechargeable battery during standby after being fully charged.

Description

Charging device for battery with battery management system for rechargeable battery

The present invention relates to a charging device for a rechargeable battery. In particular, a charging device for a rechargeable battery having a battery management system that allows the rechargeable battery to remain fully charged during standing after being fully charged.

Since the battery is an electrochemical device, its performance will gradually decrease over time. In terms of replacement manpower and shortened service life, premature loss means higher costs. A depleted battery is subject to the risk of unpredictable load loss. Under normal operation, the rate of loss of the battery is affected by the degree of maintenance at the time of fullness. Overcharging is harmful to the battery under any operating conditions.

The lithium battery charger is a voltage limiting device that is similar to a lead acid system. The difference between the two is that the voltage of each battery cell is higher, the allowable range of voltage is smaller, and there is no turbulence or floating charge when fully charged. Lead-acid batteries offer higher flexibility for voltage cut-off, but manufacturers of lithium batteries need to set high requirements because lithium batteries cannot accept overcharging. Lithium batteries are "clean" systems and only accept what they can absorb. Anything extra will be a burden.

Most batteries can be charged to 4.20V/cell and have an allowable range of +/-50mV/cell. Although higher voltages increase their capacity, the resulting battery oxidation will reduce their lifetime. More importantly, there will be safety concerns if charging exceeds 4.20V/cell.

Battery chargers for rechargeable batteries, especially lithium batteries, typically have three charging stages. The first charging phase is a trigger charge phase, the second charging phase is a constant current phase, and the third charging phase is a constant voltage phase. From the perspective of electronic technology, for the rechargeable battery, the first charging phase is the charging current limiting phase, the second charging phase is the high constant voltage phase, and the third charging phase is the low constant voltage phase. The mutual conversion of the second charging phase and the third charging phase is determined by the charging current. When the current is greater than the charging current, it is maintained in the second charging phase; when the current is less than the charging current, it is maintained in the third charging phase. This charging current is also called a switching current or a turning current.

Please refer to Figure 1. Figure 1 shows the current (I) and voltage (V) versus time for a rechargeable battery. The change in current is shown in dashed lines, and the change in voltage is shown in solid lines. The first charging phase is 0 to t1, the second charging phase is t1 to t2, and the third charging phase is t2 to t3. After t3, the rechargeable battery will no longer be charged. In the first charging phase, the current remains constant in a nearly linear relationship with respect to time as the voltage increases. In the second charging phase, the current increases significantly and remains at a certain value. At the same time, the voltage continues to increase, but its rate of increase decreases with time. When the rechargeable battery enters the third charging phase, the current will decrease with time as the voltage remains unchanged. The rechargeable battery will continue to charge until an off current reaches t3. Since no current is input to the rechargeable battery after t3, the voltage of the rechargeable battery, along with the voltage stored therein, will naturally drop.

In general, the charger uses the above cutoff current after t3 (third When the charging phase is completed, a cut off point is provided to protect the rechargeable battery from overcharging. That is, after the cutoff point shown in Figure 1, the charging process will not be performed. All rechargeable batteries have self-discharging characteristics. If the rechargeable battery is in a self-discharge state for a long period of time without power supply, the capacity of the rechargeable battery will decrease. As shown in Figure 1, the voltage begins to decrease after t3. This not only causes low power, but also affects its life and capacity.

Traditionally, a lithium battery charge control system detects a live voltage of a charged lithium battery by a voltage detector and transmits the voltage value to a microprocessor previously built into the portable device. Therefore, the microprocessor can instantly determine an appropriate charging phase based on its voltage value and confirm the state of the rechargeable battery. Furthermore, the microprocessor can control a control unit by a pulse width modulation signal to modulate the power from the connector to become a fixed current or a fixed voltage to charge the battery. Therefore, the charging process is completed by repeating the detection voltage and duty cycle modulation. However, although the charge control system has convenient charge management to charge the rechargeable battery by detecting the current capacity, it cannot control the battery capacity of the fully charged rechargeable battery.

Therefore, there is a need for a charging device that allows a rechargeable battery to remain fully charged during standing after being fully charged.

This paragraph of text extracts and compiles certain features of the present invention. Other features will Was revealed in subsequent paragraphs. The intention is to cover various modifications and similar arrangements in the spirit and scope of the appended claims.

According to an aspect of the present invention, a charging device for a rechargeable battery having a battery management system includes: a charging module electrically connected to a power source for charging the rechargeable battery; and a voltage detection a module for detecting a voltage of the rechargeable battery; and a determining module, configured to: when the voltage detecting module detects that the voltage of the rechargeable battery drops below a first preset At the voltage, the charging module is instructed to charge the rechargeable battery with an additional current until the voltage of the rechargeable battery reaches a second predetermined voltage, wherein the voltage of the rechargeable battery is due to the rechargeable battery It drops from self-discharge during rest after standing completely.

According to the present invention, the rechargeable battery is a lithium battery.

According to the present concept, the second predetermined voltage is equal to the voltage of the rechargeable battery when it is fully charged.

According to the present invention, the charging device further includes a power factor correction circuit connected between the power source and the charging module for reducing distortion of the input current and making the current and voltage in phase.

According to the present concept, the maximum value of the supplemental current is less than the current supplied to the rechargeable battery before the rechargeable battery is fully charged.

The invention will now be more specifically described by the following examples.

Please refer to FIG. 2 to FIG. 4. It discloses a preferred embodiment in accordance with the present invention. 2 is a battery tube for a rechargeable battery 20 according to the present invention. Schematic diagram of the charging device 10 of the system. 3 and 4 are graphs showing current (I) and voltage (V) versus time for charging of rechargeable battery 20 in accordance with the present invention.

In this embodiment, the rechargeable battery 20 is a lithium battery. It should be understood that the rechargeable battery 20 is not limited to being a lithium battery, and a lead acid battery may also be used. As described above, the conventional charger provides a cut-off point after the rechargeable battery is fully charged to protect the rechargeable battery from overcharging. This means that the rechargeable battery will no longer be charged after the cutoff point. However, the rechargeable battery will automatically discharge when it is left, so that the capacity of the rechargeable battery is lowered. SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a charging apparatus which allows a rechargeable battery to remain fully charged during standing after being fully charged.

The charging device 10 includes a charging module 101, a voltage detecting module 102, and a determining module 103. The charging module 101 is electrically connected to a power source 30 and used to charge the rechargeable battery 20. In this embodiment, power source 30 provides direct current (DC). In practice, however, the charging device 10 can also include an AC-DC converter for converting alternating current (AC) to direct current before supplying power to the charging module 101.

The voltage detecting module 102 is connected to the rechargeable battery 20 for detecting and monitoring the voltage of the rechargeable battery 20.

The determination module 103 is connected to the charging module 101 and the voltage detection module 102. The determination module 103 determines whether or not the rechargeable battery 20 is to be charged. If the voltage detected by the voltage detecting module 102 drops below a first predetermined voltage V ₁ , the determining module 103 will instruct the charging module 101 to charge the rechargeable battery 20 . An additional current C ₂ is charged until the voltage of the rechargeable battery 20 reaches a second predetermined voltage V ₂ . As described above, the voltage of the rechargeable battery 20 is mainly lowered by the self-discharge of the rechargeable battery 20 during standing after being fully charged.

According to the present invention, the second predetermined voltage V ₂ is equal to the voltage of the rechargeable battery 20 when it is fully charged. In other words, the second predetermined voltage V ₂ is equal to the voltage of the rechargeable battery 20 at the off current C ₁ . However, the second preset voltage V ₂ may also be set to be slightly lower than the voltage at which the rechargeable battery 20 is fully charged to prevent the rechargeable battery 20 from being overcharged. The first predetermined voltage V ₁ may be set to be 10% lower than the voltage of the rechargeable battery 20 when it is fully charged.

Please refer to FIG. 3, which shows a relationship diagram after the start of t2 in FIG. The off current C ₁ is the current supplied by the third charging phase in FIG. The off current C ₁ is the minimum current supplied to the rechargeable battery 20 by the charging module 101. The charging module 101 stops supplying power to the rechargeable battery 20 when the current in the third charging phase drops to the off current t3. At t3, the voltage of the rechargeable battery 20 is V ₂ .

Rechargeable battery 20 is no longer charged after t3, until t4, when the voltage of the rechargeable battery 20 drops to V _1, the beginning of the rechargeable battery 20 to supply a current Added C ₂ so that the rechargeable battery 20 The voltage can be increased from V ₁ to V ₂ . During the voltage increase, the supplemental current C ₂ supplied to the rechargeable battery 20 will decrease with time until the supplemental current C _{2 is} decremented to the off current C ₁ and the voltage of the rechargeable battery 20 is increased to V ₂ (t5). The maximum value of the supplemental current C ₂ may be less than the current supplied to the rechargeable battery 20 before the rechargeable battery 20 is fully charged.

Two stages of the charging process Figure 4 shows t4-t5 and t6-t7, as shown in FIG adjusting the voltage between ₂ V and V ₁ of the cycle will continue to charge the rechargeable battery 420 is removed from the charging device 10 on the .

It should be noted that the time required for the charging process of t4-t5 and t6-t7 is not always the same, which varies depending on the state of the rechargeable battery 20 and the temperature during charging.

In addition, the charging device 10 can further include a power factor correction circuit 104 connected between the power source 30 and the charging module 101 for reducing the distortion of the input current and making the current and voltage in phase.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

11‧‧‧Charging device

105‧‧‧Charging module

106‧‧‧Voltage detection module

107‧‧‧Determining module

108‧‧‧Power factor correction circuit

20‧‧‧Rechargeable battery

30‧‧‧Power supply

Figure 1 shows the current (I) and voltage (V) versus time for a rechargeable battery.

2 is a schematic view of a preferred embodiment of the present invention.

3 and 4 are graphs showing current (I) and voltage (V) versus time for a rechargeable battery during charging according to a preferred embodiment of the present invention.

10‧‧‧Charging device

101‧‧‧Charging module

102‧‧‧Voltage detection module

103‧‧‧Determining module

104‧‧‧Power factor correction circuit

20‧‧‧Rechargeable battery

30‧‧‧Power supply

Claims (5)

A charging device for a rechargeable battery having a battery management system, comprising: a charging module electrically connected to a power source for charging the rechargeable battery; and a voltage detecting module for detecting a voltage of the rechargeable battery; and a determining module, configured to indicate the charging mode when the voltage detecting module detects that the voltage of the rechargeable battery drops below a first predetermined voltage The group charges the rechargeable battery with an additional current until the voltage of the rechargeable battery reaches a second preset voltage, wherein the voltage of the rechargeable battery is static after the rechargeable battery is fully charged During the set period, it drops due to self-discharge. The charging device of claim 1, wherein the rechargeable battery is a lithium battery. The charging device of claim 1, wherein the second predetermined voltage is equal to a voltage of the rechargeable battery when fully charged. The charging device of claim 1, further comprising a power factor correction circuit coupled between the power source and the charging module for reducing distortion of the input current and allowing the current to be in phase with the voltage. The charging device of claim 1, wherein the maximum value of the supplemental current is less than a current supplied to the rechargeable battery before the rechargeable battery is fully charged.