DE2928503A1 - Auxiliary battery charger for no break power supply - is for charging individual sections to gassing point to maintain battery performance - Google Patents

Abstract

The application is to uninterruptable power supplies for dc loads which have to operate within close limits of maximum and minimum voltage. The main rectifier and regulator (1) feeds the load (2), and also charges the battery (3). As the battery delivers no current under normal conditions, its output performance may deteriorate, for example due to high local acid concentration in a lead acid cell. To avoid this condition each battery section (3.1, 3.2,3.3) in turn is charged to the gassing point in order to give good mixing of the electrolyte. By charging one section at a time the output voltage is maintained within the limits defined for the load. The auxiliary charger (4) is typically an unregulated dc supply. It is switched (5) in turn to each battery section. Switching may be determined by a timer, by evolution of gas, or some similar means.

Description

Method and device for full and / or compensation

Charging of multi-cell accumulator batteries with limited total voltage The invention relates to a method and a device for full and / or equalization Charging of multi-cell accumulator batteries with limited total voltage for Consumers that require an uninterruptible power supply and parallel to this with a power supply device, in particular with a regulated rectifier Constant voltage output and current limitation, and an accumulator battery switched are.

A multitude of electrical installations require an uninterruptible one Power supply. The most important systems of this type are telecommunications, signaling and Monitoring systems and electronic data processing systems are listed. Around this in the event of mains voltage failures or other malfunctions in the power supply equipment ensure, accumulator batteries are used, which in the event of a failure Supply of the connected consumers without interruption or within a very short time Take over time.

In general, standby parallel operation is used in such systems applied. Here are the power supply device, the consumer and the battery connected in parallel. The power supply is almost exclusively regulated Rectifier with constant voltage output and current limitation (IU characteristic). He must be dimensioned so that it feeds all connected consumers and at the same time can recharge a discharged battery. The battery is to be designed so that corresponding the respective consumer demands the voltage is above a permissible minimum value during a certain period of time.

For the consumer there is a general requirement that a certain Minimum voltage not undershot and a certain maximum voltage not exceeded may be. For the battery this means in standby parallel operation Limitation of the charging voltage to a certain maximum value. A lead battery can with a maximum charging voltage of 2.23 V / cell when fully charged can be obtained. When discharging, however, concentrated sulfuric acid is added to the electrolyte withdrawn and chemically bound in the electrodes in the form of lead sulfate. In the Charging, the lead sulfate is broken down again and the sulfuric acid released returned in concentrated form to the electrolyte. As a result of the high Density of concentrated sulfuric acid (approx. 1.84 kg / l) compared to free sulfuric acid inside the cell (approx. 1.10 to 1.20 kg / l depending on the degree of discharge) it initially sinks into the lower part of the cell. This creates a layer of acid density that if it persists for a long time, performance and service life are adversely affected.

It is known that mixing is achieved within a short time can be charged by charging in the gassing area of the battery. There is the problem, however, that significant gas development only occurs when there is a voltage of more than 2.4 V / cell starts. This value is generally higher than that for the Consumer permissible maximum voltage. In practical standby parallel operation it is not possible to remove the undesired acid density layer in lead batteries to avoid.

With an alkaline battery, there is a risk of density stratification of the electrolyte generally not even with frequent discharges. Certain nickel compounds form in the positive Electrode only when charging into the Gassing area at a voltage of approx. 1.7 V / cell. During the subsequent continuous charging respectively.

with trickle charge with a voltage of approx. 1.38 to 1.40 V / cell but they gradually degrade again. This has the consequence that in the event of a discharge only a reduced voltage is supplied.

In order to prevent this, suitable discharges must also be used in the absence of discharges Time intervals in the gassing area up to approx. 1.7 V / cell can be charged to the formation to ensure such certain nickel compounds. This value is also general above the maximum voltage permissible for the consumer.

In order to be able to meet the battery-specific requirements, complex power supply devices and switching devices are provided. Ever according to the importance of the system, consumer power, bridging time and size of the The voltage range permissible for the consumer has different Variants of standby parallel operation as well as uninterrupted or brief switching operation introduced. With the exception of redundant systems that allow a battery to be switched off for full or equalization charging they only inadequately meet the relevant technical battery requirements.

The invention is based on the object of a simple method and a device for full and / or equalization charge of multi-cell accumulator batteries to propose if the total voltage is limited, which enables battery-compatible Carry out charges and equalization charges while avoiding the disadvantages mentioned. In particular, the maximum voltage permissible for the connected consumers should be should not be exceeded and the uninterrupted power supply of the consumer should be in the event of mains voltage failures or malfunctions in the power supply unit stay.

The object is achieved in that individual or Cells of the battery combined into groups, dividing the total voltage in at least two partial voltages at a time interval one after the other while observing of the permissible total voltage, whereby during the charging process in no cell or cell group of the battery falls below the open-circuit voltage. By attaching voltage taps to the battery and the associated approximately even division of the total stress into two or more partial stresses it is possible to carry out charging processes below the maximum voltage permitted for the consumer to be carried out, but still in the gassing area of the cell or cell group, that is charged, in order to create an acid density layer in expensive accumulators to avoid or the formation of certain nickel compounds in alkaline batteries to favor. The number of taps depends on the maximum permissible voltage on the consumers and the number of cells in the battery.

While it is normally sought that the cells of a battery have the same voltages in the charging area, in the procedure according to the invention consciously at appropriate time intervals while maintaining the permissible total voltage forced a shift in the individual cell groups. The prerequisite is that during this manipulation the rest voltage did not fall below the rest voltage in any group will. This is e.g.

for stationary lead batteries, depending on the type, 2.04 to 2.08 V / cell.

If it is limited to a minimum value of 2.1 V / cell, it is guaranteed that that discharges do not occur. The open circuit voltage is not the same with steel batteries precisely definable. To avoid a discharge, a voltage of 1.30 up to 1.35 V / cell are not exceeded.

When a charging voltage of 2.40 to 2.45 V / cell is exceeded Lead accumulators occur in the cell group to be charged according to the invention significant gas development. The end-of-charge voltage is 2.65 to 2.70 V / cell achieved. In the area between the start of gassing and the final voltage, the the desired mixing of the electrolyte with rising gas bubbles.

Steel accumulators require to reactivate the active Masses of the electrodes allow charging up to a voltage of approx.

1.7 V / cell.

It is beneficial to have the gradual charge set in automatically To be carried out at intervals and / or after previous discharges. Here can the charging time can be limited purely time-dependent or can be used to initiate a specific After charging time, reaching or exceeding a specified charging voltage or the use of gas development can be used. The gradual charging of the cells or cell groups can be controlled by a program switch or a sequential circuit will.

The inventive device for performing full and / or Equalizing charges on multi-cell accumulator batteries with limited total voltage is characterized in that the battery voltage taps are used to subdivide the Battery in cells and / or cell groups of approximately the same size that can be charged one after the other having. The division is expediently in such a large number of cell groups made that at least one of these can be charged up to the end-of-charge voltage, without falling below the no-load voltage in the other cell groups.

According to a preferred embodiment of the invention, an active Group equalization charge can be carried out if a separate, from the system's power supply independent additional rectifier is provided. It can advantageously be between the additional rectifier and the voltage taps are connected to a cleavage element, in particular a door switch be.

To carry out a passive group equalization charge in which the power supply device of the system at the same time the supply device for the to be charged 3 battery is proposed according to the invention for the individual cell groups to connect ohmic resistors in parallel to the battery. The passive group compensation charging is recommended for power supply systems with smaller batteries and regulated Power supply rectifier.

The activation can take place in such a way that at least one group of cells The associated resistor is not connected in parallel for full or equalization charging will. Appropriately, the ohmic resistors are dimensioned so that In the cell group intended for charging, a charging current flows that determines the cell voltage increases to the end-of-charge value and within the limits of the gassing area Charging currents lies, with the rest voltage not falling below the no-load voltage in the other cell groups and the maximum permissible voltage of the entire battery is not exceeded. The ohmic resistances can be manually or automatically parallel to the cell groups that are not intended for full or equalization charging.

The invention is particularly advantageous in the case of voltage-limited pure Charges, e.g. from vehicle drive batteries to chargers with IU characteristics or applicable to parallel charges with constant voltage.

Further details, features and advantages of the subject matter of the invention emerge from the following description of the drawing, in the schematic in the form of block diagrams Chargers shown are. The drawing shows: FIG. 1 the basic arrangement of a device for charging a battery in the form of a circuit diagram, FIG. 2 shows a modified embodiment a device for charging a battery in the form of a basic circuit diagram, Fig. 3 diagrams showing the shift in cell voltages when dividing the battery show in two to five cell groups for lead batteries and Fig. 4 similar Diagrams according to FIG. 3 for steel batteries.

Fig. 1 of the drawing illustrates the basic circuit diagram for an active one Charging or equalizing charge of an accumulator battery with limited total voltage using the example of a division into three cell groups due to the presence of two Tapped on the battery.

min Power supply rectifier 1 in a regulated version with IU characteristic feeds a consumer 2 and charges the battery 3 or keeps it charged. An auxiliary rectifier 4 can optionally switch to the cell groups via a step switch 5 3.1 to 3.3 of the battery 3 are switched. Instead of the step switch 5 you can contactors or other switching devices can also be used.

The auxiliary rectifier 4 only needs a fraction in terms of voltage the nominal voltage, in the example shown, 1/3 of the nominal voltage. The current must be adjusted to the battery capacity so that the im Gassing range for the respective battery type, permissible charging current according to DIN 57 510 / VDE 0510 is not exceeded.

Provided the maximum permissible total voltage is charging a group of cells up to the end-of-charge voltage of 2.65 to 2.7 V / cell, use is recommended of an auxiliary rectifier in an unregulated version with a W characteristic according to DIN 41 774 for lead batteries and 41 775 for steel batteries. Otherwise is a Provide voltage limitation, e.g. in the form of an IU characteristic according to DIN 41 773 or in the form of a WU characteristic. The U part of the characteristic is not open to limit the gassing voltage of the cell group to be charged, but to one Value resulting from the maximum permissible total voltage and the subdivision of the Total battery in cell groups.

With regard to the charging current, it is advisable to design the auxiliary rectifier corresponding to the battery charging current permitted in the gassing area. This is also true towards unregulated devices, since it can be assumed that before switching on of the auxiliary rectifier, the battery is largely charged.

The auxiliary rectifier 4 is used for charging by means of the step switch 5, for example, initially with the cell group 3.1 of the battery via the switch position 1-1 related. Afterwards it is charged into the gassing area can then charge the cell groups 3.2 and 3.3 one after the other in the same way by moving the step switch 5 into the corresponding switch positions will. This can also be done automatically.

Fig. 2 of the drawing illustrates the basic circuit diagram for passive Charging or equalizing charge of an accumulator battery with limited total voltage using the example of a division into three cell groups. The passive group equalization charge is recommended for Power supply systems with smaller batteries and regulated power supply, rectifier. The purpose is the same as with the above-described active group balancing charge. Using the example of a battery with two taps after 1/3 and 2/3 of the cells used, this then results Block diagram of the #ig. 2.

The power supply rectifier 1, usually in a regulated version with IU characteristic, feeds the Yersraucizer 2 and charges the battery 3 or holds it when charged. The individual cells Öru; o; The 3.1 to 3.3. are ohmic resistances 4.1 to 4.3 connected in parallel via switching elements 5.1 to 5.3. For the purpose of compensation charge of a cell group, the switch assigned to it remains open while the other switches are closed. In the cell groups that have an ohmic Resistance is connected in parallel, a voltage drop occurs. Through this the power supply rectifier 1 a constant total voltage is maintained, this leads to a corresponding increase in voltage in the cell group, which no resistor is connected in parallel.

The resistors 4.1 to 4.3 are to be designed so that in the to be charged Cell group of the permissible charging current in the gassing area according to DIN 57 510 / VDE 0510 is not exceeded. It should also be taken into account that in the cell groups with a resistor connected in parallel, the open-circuit voltage is not undershot. In addition, the battery is to be divided into as many cell groups as there are Requirements the end-of-charge voltage of the cell group to be charged must be achieved can.

The shift in cell voltages when the battery is divided in two to five cell groups, depending on the permissible mean cell voltage, Fig. 3 of the drawing shows for lead batteries and Fig. 4 for steel batteries. Included relates to image 3a of FIG. 3 a division into two groups of cells (a voltage tap).

Figure 3b concerns the division into three cell groups (two voltage taps). Figure 3c shows the division into four cell groups (three voltage taps). image 3d shows the division into five cell groups with four voltage taps.

In the same way, Fig. 4 of the drawing in Figs. 4a, Xb, 4c and 4d subdivided. Both in Fig. 3 and in Fig. 4 of the drawing means x: Charging voltage of the cell group on boost charge y: Charging voltage of the other cell groups z: maximum permissible mean cell voltage.

The frequency of equalization charges depends on the respective operating conditions addicted. You can do this manually, purely time-dependent or dependent on certain operating states or a combination of different criteria. The duration of the compensation charges can be fixed or determined by certain battery states, such as exceeding made dependent on a certain charging voltage or the use of gas development will.

In the last two cases, additional use is recommended of a time drive. Switching the auxiliary rectifier from a group of cells the other can be done manually, by a sequential circuit, a program switch or the like take place.

Claims (12)

Claims: f sß 1. A process for full and / or equalization charge of multi-row accumulator batteries with limited total voltage for consumers, which require an uninterruptible power supply and for this purpose in parallel with a Power supply device, especially a regulated rectifier with constant voltage output and current limitation, and an accumulator battery are connected, d a d u r c h e k e k e k e n n e i n e t that individual cells or cells combined into groups (3.1 to 3.3) of the battery (3), dividing the total voltage into at least two partial voltages at a time interval one after the other in compliance with the permissible Total voltage to be charged, with no cell or during charging Cell group (3.1 to 3.3) of the battery (3) the open circuit voltage falls below. 2. The method according to claim 1, characterized in that the stepwise Charge automatically at specified time intervals and / or according to previous ones Discharges is carried out. 3. The method according to claim 1 and 2, characterized in that the Loading time is limited purely time-dependent or that to initiate a certain Recharge time reaching or exceeding a specified charging voltage or the use of gas development is used. 4. The method according to any one of claims 1 to 3, characterized in that that the gradual charging of the cells or cell groups by a program switch or a sequential circuit is controlled. 5. Device for performing the method according to one of the claims 1 to 4, characterized in that the battery () has voltage taps for subdivision of the battery in cells or cell groups of approximately the same size that can be charged one after the other having. 6. Apparatus according to claim », characterized in that the subdivision is made in so many cell groups that at least one of these up to Charge-charging voltage can be charged without the open-circuit voltage in the other cell groups is fallen below. 7. Apparatus according to claim 5 and 6, characterized by an additional rectifier (4) for the cargo. 8. Apparatus according to claim 7, characterized in that between the additional rectifier (4) and the voltage taps are connected to a switching element (5) is. 9. Apparatus according to claim 8, characterized in that the switching element (5) is a multiple switch. 10. Apparatus according to claim 5 and, characterized in that to the individual cell groups (3.1 to 3.3) of the battery (3) ohmic resistances (4.1 to 4.3) can be connected in parallel. 11. The device according to claim 10, characterized in that the Connection takes place in such a way that at least one group of cells for full or equalization charging the assigned resistor is not connected in parallel. 12. Apparatus according to claim 10 and 11, characterized in that the ohmic resistors (4.1 to 4.3) are dimensioned so that in the for the Charge provided cell group a charging current flows, which increases the cell voltage the end-of-charge value increases and within the limits of the gassing area permissible charging currents.