Glossary 

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Current recording                       

The current recording is calibrated to the lower current range. For this reason, deviations occur in the range of maximum currents. We would like to point out that your purchase is not specifically a measuring device, but rather a convenient system manager with many display functions.

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Deep discharge protection, central                       

According to the factory settings, the deep discharge protection is controlled by the SOC algorithm. Frequent deep discharge causes your battery to lose capacity in the long term due to sulphation. The deep discharge protection of the system manager disconnects the loads and then reconnects them after the battery has recharged sufficiently.
The loads can also be connected or disconnected manually. As such, the system manager assumes the role of a main switch.

If the voltage falls below a specified fixed value, all loads are disconnected, regardless of the programmed values or manual settings (emergency disconnect).
The functions of the system manager can be switched to voltage control and then freely programmed. If this function is selected, the threshold values relative to the battery voltage are used as control values. The SOC control, which is better at indicating the critical acid density than voltage values, is then deactivated.

Deep discharge warning (LVW)

If the LVW threshold value (limit) is fallen short of, the deep discharge warning is activated and if the limit is exceeded, this warning is deactivated once more. It serves to warn the user against deactivation of the load output in the event of continuing discharge of the battery. Depending on the controller, the warning is either conveyed by a flashing LED or a flashing indication in the display. 

Display               

A two-line display gives you information on important system parameters via the status display. The first line always shows the state of charge, battery voltage, charge current and discharge current (to a rough degree of accuracy).
The second line gives you information on the system parameters and statuses with detailed values and descriptions which alternate.
The display functions correctly within a temperature range specified by the manufacturer. If this operating temperature range is breached, errors may occur, but these are corrected again once the temperature returns within the range. The storage temperature must not be outside of the specified range, however.

Double fault                      

see Single and double faults

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Equalisation charging                       

see Quick charging and equalisation charging  

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Fault finding                                             

see Malfunctions and fault finding

Flammability

The system manager is made entirely out of non-flammable or self-extinguishing materials. Even in unforeseeable fault situations, a fire cannot be started so long as no flammable materials are stored in close proximity to the system manager and the system manager has been mounted on a fireproof surface.

Fuse, hardware

The system manager is protected by fuses well over the rated currents. The rated current of the system manager must therefore not be taken from the fuse values. The output ranges must be taken from the SOAR diagram.

The fuses are connected in parallel. The value is set so high so that the fuses are not also triggered if too high a current flows for just a short time. Before the fuses are triggered, the electronic fuse will prevent the excess flow of current.

The fuses only serve to protect the system manager from incorrect polarity. After an incorrect polarity, both fuses have to be replaced. In addition, the system safety is significantly increased by the fact that even if the electronics fail, no dangerous operating situations can come about.

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Grounding, negative                       

Grounding the negative pole bridges the actuators which are necessary for the controller and the fuse. This also means that the internal protection devices are deactivated, which may lead to the system manager being destroyed.
Only one of the negative connections of the module, battery and load components may be grounded.

If your solar system already provides a minus-side earth, only one component (in this example, battery-minus) may be connected to this earth. Connecting to other minus connections (module or load) bridges control elements and the fuse. This causes malfunctions or even irreparable damage to the system manager.

In systems with preset load–minus–earth (e.g. grounding antennas) all other components must be floating.

Grounding, positive

If the plus side is selected for grounding, it can also be used as an earth for all system components. All plus conductors are internally interconnected in any case.

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Malfunctions and fault finding                                                                 

The system manager has been designed for years of continuous trouble-free operation. Nevertheless, faults may occur. In many cases, however, the system manager is not at the root of the problem, rather the peripheral components. The following description of some well-known problems should help the installer and operator to isolate the problem, so that the system can begin operating again as quickly as possible and to avoid unnecessary costs. Of course, not all possible causes of problems can be listed here. However, most of the normal problems encountered with the system manager can be found in the list below. Only return the system manager when you are absolutely sure that none of the problems listed below is responsible for the fault.
A range of measures protect the system manager from irreparable damage. In spite of this, you must take great care to ensure that the system manager is used properly. Some malfunctions are indicated via the LCD display. However, only faults for which the system is properly installed can be displayed. If faults other than those described occur, first check whether the system manager is connected to the battery, the module and the loads with the correct polarity. Then check whether the fuses are faulty. The system manager automatically switches off the load when any fault occurs.

Mixing of acids, monthly         

In the case of batteries with a low depth of discharge the end-of-charge voltage is raised for a limited time every 30 days. When this happens, depending on the composition of the electrolyte, either boost charging or equalisation charging is activated. This function prevents harmful acid stratification, which comes about particularly after a long period in the trickle charge phase.

MPP tracking 

What is MPP tracking (MPPT)?
MPPT stands for "Maximum Power Point Tracking". This describes a process by means of which the solar module is always operated at the point of maximum possible power. Because the point the maximum power can vary depending on the operating mode and the local conditions, and because it changes in the course of the day, the term "tracking" is used, i.e. the tracking of this point.

Why have MPP tracking? The diagram alongside shows the IU characteristic curve for a typical solar module. This curve is essentially determined by the module type, temperature and irradiation conditions. When a certain voltage is applied to the solar module, it can be operated. The current that flows can be seen at the intersection of the applied voltage and the module characteristic curve shown in the diagram. The resulting output of the solar module is found by multiplying the applied voltage by the resulting module current.

IU characteristic curve for a typical crystalline 50 Wp solar module with 36 cells

Depending on the relevant module characteristic curve and applied voltage, therefore, the solar module’s output can differ. The second curve in the diagram plots the output of the solar module across the applied voltage range. It can be seen that at first this also increases as the voltage increases. It then reaches a maximum before finally falling again. The purpose of MPP tracking is to find this maximum power point and then to operate the module at this point.

MPP tracking with solar charge controllers is based on the use of DC-DC transformers as solar charge controllers, which are able to supply a different voltage to the solar module input than is available from the battery output. This is not possible with conventional switching charge controllers, such as shunt and series controllers. These switching charge controllers can only operate the solar module at one fixed output point and are unable to track the point of maximum power output.

A solar charge controller with MPP tracking is an optimised DC-DC converter that is able to supply a different voltage to the solar module input than is available at the battery output. The efficient Steca MPP tracking algorithm allows this charge controller to select and adjust the working point of the solar module, even while the battery voltage remains constant, in such a way that the maximum possible power from the solar module can always be used in the system.

Unlike conventional switching charge controllers, an MPP solar charge controller is therefore able to track the solar module’s momentary maximum power point. As a result, an additional yield can be generated from the solar module under certain circumstances. This is the key advantage of MPP trackers compared to switching solar charge controllers.

When should charge controllers with MPP tracking be used?
Switching solar charge controllers such as shunt and series controllers operate the solar module at the battery voltage. This means that the battery voltage is present at the solar module and it determines the point at which the module operates. Conventional solar modules that have a multiple of 36 cells are now usually designed in a way that they automatically operate at the maximum power point when the battery voltage is supplied. This allows for the solar module’s power to be used optimally.

But if solar modules are used that are not optimised for stand-alone systems and have more than 36 cells, the solar module is no longer able to operate at the maximum power point. MPP trackers should be used as solar charge controllers in this case so that the maximum possible power output can be obtained from these solar modules. This typically applies when solar modules that were actually intended for use in grid-connected photovoltaic systems are used to charge a 12 V battery. With the aid of an MPP tracker, these can be used to charge batteries in the optimum way without any problems.

An MPP tracker should also be used as a solar charge controller if a 12 V or 24 V battery is to be charged using a thin-film module. These modules often have very high charge cut-off voltages, which need to be adjusted to the battery voltage via an MPP tracker.

Notes on choosing suitable solar modules
If the maximum input voltage is exceeded even for a short time by the connected solar module, the solar charge controller will be damaged beyond repair and can never be used again. This will NOT constitute a guarantee claim, the charge controller must then be replaced at the customer's expense.

The essential value for choosing a solar module is the open circuit voltage (U_oc). The open circuit voltage of the solar module is dependent on the ambient temperature. Information on the open circuit voltage of the solar module and on temperature dependence can be found in the data sheet of the solar module. The lower the ambient temperature, the higher the open circuit voltage of the solar module.

The maximum possible open circuit voltage of the solar module array must never exceed the maximum input voltage of the solar charge controller.

To dimension the module array correctly, first of all find the minimum anticipated ambient temperature. The solar module open circuit voltage value specified on the data sheet must now be converted for this minimum ambient temperature. The resulting value must not exceed the solar charge controller’s maximum input voltage under any circumstances.

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Operating keypad                                          

Target values can be individually adjusted using the keys under the cover strip. The freely programmable values can only be adjusted within specified ranges. These ranges are chosen in such a way that even the extreme values will generally not lead to serious damage to lead-acid batteries.
The control elements are accessible, however, without child protection (code). We therefore recommend, in your own interests, making the system manager and the battery room inaccessible to children.

Output ranges                        

The system manager can be used for a broad range of output and temperature applications. It automatically ascertains its maximum permissible own temperature, and only disconnects the loads if this is exceeded. This means that the entire cooling surface of the power losses which is produced during charging is made available. However, in order that the loads are not disconnected in the case of overtemperature when this is undesired, it is essential to remain within the safe operating area (SOAR) when dimensioning the system. The SOAR is the entire range to the left underneath the relevant temperature curve. The system should be dimensioned in such a way that the ambient temperature curveis not exceeded at the maximum charge and discharge currents. The system manager is designed in such a way that, at an ambient temperature of 20 °C and if correctly installed, it can process the rated currents of the module and the load at the same time (see type plate). These rated currents are equal to 100% in the diagram.

• Example 1
  
  If only a maximum of 40% of its rated load current flows over a day, the module current may receive 120% of its rated current. This means, for the controller type 245 with a rated current of 45 A at a discharge of 45 A * 40% = 18 A may be charged at the same time as 45 A * 120% = 54 A, so long as the ambient temperature does not exceed 20 °C when the system is under this load. If, however, this SOAR limit is exceeded, the system manager disconnects the load. Now the discharge current is 45 A * 0% = 0 A and the charge current may reach 45 A * 130% = 58.5 A. The system may therefore not be planned with a solar generator which is too large for the system manager to process at the maximum temperature.
• Example 2
  Conversely, at night the discharge current is 130%, since no charge current can flow (0% rated module current).
  
  
• Example 3
  
  At a high ambient temperature of 50 °C, 20% of the discharge current could still be used at 70% of the rated charge current. This example shows that by reducing the maximum charge and discharge currents, the system manager can be operated up to the limits of storage temperature range.
• Tip
  
  When installing the system manager in the switching cabinet, the maximum cabinet interior temperatures must be taken into account. These are higher than the ambient temperatures, as the system manager and any other measuring and controlling devices which may be present generate lost heat.

Overload protection                      

The overload protection prevents uncontrolled gassing in the battery cells. The production of gas depends on the acid temperature and the cell voltage. For this reason, the system manager monitors the ambient temperature and adjusts the battery voltage to it. The overload protection, and therefore also the voltage limitation, does not depend on the battery's state of charge, as the decomposition of the electrolyte depends solely on the voltage and the temperature. This means that the battery charging is limited although the battery has not yet been fully charged. Overcharging a battery leads to uncontrolled gassing. This results in the electrolyte decomposing into oxygen and hydrogen. The consequences are damaging oxidation processes and mechanical damage, as the gas bubbles erode active mass on the lead plates.

Uncontrolled gassing in closed batteries (e.g. gel and flowbatteries) is even more serious, as the gas pressure which develops can even destroy the battery casing. Frequent overcharging damages the battery bank. The charging process and the overcharge protection are therefore controlled by a new hybrid actuator with pulse-width modulation to guarantee gentle charging of the battery. The trickle charge voltage, in particular, should not be set too high. If you do want to programme this value individually, you should note there commendations of the battery manufacturer.

Overvoltage protection

Lightning protection cannot be provided in a system manager of this size for reasons of cost and space. Lightning protection must be provided when the system is installed and adjusted to the local conditions. However, some measures have been taken in order to compensate atmospheric surge voltages. In most applications, this protection is sufficient on its own. However, in the case of very expensive appliances, we recommend having additional protection.

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Quick charging and equalisation charging                                                                                           

After the state of charge falls below a specified threshold, the system manager raises the end-of-charge voltage in the next charge cycle for a limited period. When it does so, the countdown is only activated once the desired end-of-charge voltage has almost been reached. Attention should be paid that the solar generator can also make sufficient charge current available at the corresponding end-of-charge voltages.
Boost charging can be activated manually for a limited time.

• Note
  
  If the end-of-charge voltage is set too high in relation to the generator voltage (less the cable losses), there is a chance that the countdown will never start and your battery will not be controlled when it is charged.

Equalisation charging is only possible and can only be programmed if a battery has been configured with a liquid electrolyte. It is activated if the battery's state of charge falls below a lower threshold.

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Reset voltage (LVR)        

If the LVR threshold value (limit) is fallen short of, the previously active deep discharge protection of the load output is automatically deactivated once more. At this point, the solar charge controller's display also switches back to the normal display mode. Loads connected to the solar charge controller can be operated again once the LVR threshold value is reached. 

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Safety measures                       

All safety measures which are taken to protect the system manager can not prevent the effects of a faulty installation of a component outside the system manager. We therefore strongly recommend installing a fuse directly on the battery pole in order to protect against short circuits between the battery and the system manager.

Short-circuit fuse, electronic                      

An electronic short-circuit fuse prevents the system manager being destroyed and also prevents the fuse from being triggered in the case of short-circuits at the solar generator and at the load output. This fault is indicated as 'load current' (load overcurrent) on the display. Once the fault has been repaired, the system manager automatically returns to normal operation after approx. 30 seconds.

Single and double faults                                                            

The system manager is protected using appropriate measures, such as fuses, against single faults (e.g. load short-circuit, incorrect battery wiring, incorrect module wiring etc.).

However, some double faults can lead to the system manager and components connected to it (loads, modules) being destroyed. Some examples of double faults are:

• incorrectly wired batteries at the solar input
• one battery cable at the module input and the other at the load output
• an incorrect source (230 V electricity grid) at the solar input 

SOC determination

The state of charge is the basis for most control and monitoring functions. If system components are connected directly to the battery, the state of charge can only be ascertained with the aid of optional shunts.

The state of charge always relates to the available capacity which the battery has just received based on its age. Thus an SOC of 50% does not mean that half of the battery's rated capacity is still available, rather just half of the capacity which the battery still has at that time. The state of charge does not depend on the battery voltage, rather from the amount of energy it has extracted. Commercially available charge controllers normally determine an end-of-discharge voltage which only equals the depth of discharge in a certain operating conditions. When discharging, the rated acid density is reduced and sulphates (salt crystals) accumulate on the battery plates. If the battery is discharged too deeply, however, this build-up of crystals leads to damaging sulphation which greatly reduces the battery capacity, thus rendering the battery unfit for storing energy. However, the normal measuring methods (Ah balancing, measuring acid density) are complex and cost-intensive, and are therefore rarely integrated into charge controllers.

If generators or loads are connected directly to the battery without shunts, the SOC determination is distorted. In order for the battery to remain protected against deep discharge despite falsely calculated values, there are certain values which the voltage cannot fall below.

However, the system manager can be switched to voltage control so that it operates like a conventional charge controller. The voltage monitoring is recommended if other generators aside from the system manager charge or discharge the battery, or if loads, e.g. an inverter, are directly connected to the battery.

System voltage

The system manager sets itself to a system voltage of 12 V or 24 V automatically. The battery must be connected first in order for it to do so.
There are two controller options for a system voltage of 12 V/24 V or 48 V. Automatic recognition is only carried out with system voltages smaller than 30 V. For 48 V systems, a different model with voltage-proof components is required. You can tell from the imprint on the casing whether your system manager is suitable for the desired voltage.

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Temperature tracking of the end-of-charge voltage                                             

As the battery temperature increases, the optimum end-of-charge voltage of lead-acid batteries decreases. At high battery temperatures, a constantly set end-of-charge voltage would lead to uncontrolled gassing. Therefore, temperature tracking automatically reduces the end-of-charge voltage at high temperatures and raises it at low temperatures.
The temperature control adjusts to all end-of-charge voltages (flat, boost, equal).
The integrated sensor is easy to install and requires little maintenance, and can be used in any system under the following conditions:

• the system manager and the battery must be in the same room
• the accuracy of the temperature is limited, although complex calculations compensate for the self-heating of the system manager. Nevertheless, the room temperature only corresponds with the battery pole temperature within a certain (large) range.

It is possible to install an external sensor, however.

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Voltage recording                       

A special measurement process renders battery sensor lines. The voltage drop on the battery line is compensated for after the first full charge. This means that an additional sensor is not required, the installation is simplified and the system's reliability is improved, for there is no chance of a sensor breaking. The measurement accuracy is not as high as with sensor cables, however. Nevertheless, we point out that at a temperature coefficient of approx. 25 mV per 1 °C (end-of-charge voltage is changed at this ambient temperature in a 12 V system) a tolerance of 100 mV corresponds with a temperature deviation of 4 °C. Such low deviations are not enough to bring about any negative effects on the battery.

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