Although in principle it seems that in an installation of photovoltaic solar energy just need solar modules and batteries, there is a key element in these facilities is what ensures that, in the charging process as in the discharge accumulators, is made so that they are always within the correct operating conditions: the charge controller.
Solar panels are designed so that they can give a higher than the end voltage battery charging voltage. This ensures that the solar panels are always able to charge the battery, even when the temperature of the battery cells is high and decreased voltage generated occurs.
This surge has two drawbacks:
- On the one hand, a small part of the theoretical maximum power that can give the photovoltaic panel (10%), you would get if I worked a little higher than those imposed by the battery voltage is lost.
- On the other hand, when the battery reaches its fully charged state, will not reach its full potential can theoretically give the solar panel, and it will continue trying to inject energy to the battery terminals, resulting in an overload that will hurt the battery that can damage.
The charge controller has the mission to regulate the current absorbed by the battery so that you never dangerously overloaded. Therefore, detects and constantly measures the battery voltage, measuring its charge and if it reaches a set value previously set corresponding to the value of maximum permissible voltage cuts off the flow of current to the battery or well let pass only a portion to keep it in a state of full charge, do not overdo it. This minimum current is called float current and occurs when the battery is fully charged and receives just enough to keep it in that state (which, over long periods, compensate the self-discharge) energy.
The parameters defining a regulator are:
- Maximum voltage or maximum voltage admitted regulation is the value of maximum voltage regulator can be applied to the battery.
- Range Upper Hysteresis: The difference between the maximum voltage regulation and voltage regulator that allows the passage of all the current produced by solar panels. For an intermediate voltage value, the regulator passes a fraction of the current produced by the photovoltaic panels, which is smaller the closer the terminal voltage of the battery to the maximum value of regulation.
- Voltage disconnection: voltage at which consumer loads to avoid battery sobredescàrrega automatically disconnect.
- Lower hysteresis range: The difference between the voltage disconnect and voltage that is allowed to connect consumption back to the battery.
The following parameters define the most common benefits charge controllers used in the autonomous photovoltaic solar installations
- Overload Protection accumulator (high cutting): This is the basic function of the regulator. Prevents the battery hot water from the electrolyte is lost and the plates rust.
- Low Battery Alarm: audible indicators / lights indicating that the battery is sufficiently discharged. From this point, the user can moderate consumption, which will prevent harmful and excessive discharge of the accumulator.
- Logout low battery (cutting down): This function makes the cut regulator power supply to consumption if the level of battery charge is too low and therefore runs the risk of deep discharge, made which create problems sulfation.
- Short Circuit Protection: This feature allows a fuse, protecting the regulator and the output of the accumulator to suffer high currents in case of short circuit in one of the consumer circuits of the installation.
- Display Function: Most controllers have a visual system that allows information on the status of the installation, simply indicators saying the panels are giving current, if the battery is charged or discharged, or more carefully through indicators of current load levels, battery voltage ...
There are different types of controllers depending on the operating principle having
Charge Regulators parallel type (shunt)
base their operation in a transistor that derives current from the modules into a resistive load dissipation. Sets battery voltage values for which this deviation is intermittent to achieve and maintain the battery at maximum load (floating) way.
This system causes heating of the same regulator, which causes wear and loss and therefore this type regulators have limited the current work a few amps and, therefore, shall be valid for small photovoltaic installations.
Charge regulators type series
This type of regulators base their operation on the interruption of power to the battery, depending on the voltage. With current technologies, this switch is progressive, so that you can send to have different load levels. Float current can be done by maintaining a low charging current or charging switching moments and moments no load to favor no battery gassing.
This type of regulators are connected in series between the panels and the battery and do not dissipate heat as may be rather small and can be mounted indoors if necessary.
Other models of the same type regulators, used in large installations, divert the flow of the panels in other circuits when the batteries are charged to use this energy for other uses.
Other models automatically disconnecting the solar panels or groups of photovoltaic panels as the battery voltage increases, to pass only the necessary current and never in excess.
Many charge controllers carry incorporated other features for viewing and controlling the operation of the solar photovoltaic installation such as: volt and ammeters mm; alarms for low battery voltage; temperature sensor that automatically adjusts the value of the maximum load voltage; Automatic circuit disconnects low voltage consumption; ampere-hour counters; digital displays; data acquisition module; follower control module with maximum power point, etc.
An especially important element incorporating many regulators is a blocking diode which allows current flow in one direction from the panels on drums and not the contrary. This diode is necessary when solar radiation is low and the battery voltage is higher than photovoltaic panels, this prevents the battery by photovoltaic solar panels is discharged. Do not confuse this with the blocking diode bypass diode (variant) of photovoltaic modules as the functions they perform are very different.
If by accident or insulation fault there is an error in the protection system grounding, the current can flow in the opposite direction to normal and pass through a solar panel or group of solar panels before fleeing by taking of Earth. In these cases, the presence of the blocking diode is very important to prevent damage to the photovoltaic modules.
A very good insulation and good safely grounded could avoid the need to install the blocking diode. As the blocking diode produces an additional voltage drop of 0.5 to 1 V, is one more reason to design the tension than necessary panels to charge the batteries.
Regulators cargo tracking maximum power
This is the most sophisticated version of the regulators on the market, as it incorporates a coriente DC to AC at the output of the solar modules current ce converter, allowing isolate the voltage of the photovoltaic module voltage the batteries . In this way, the modules can work at their maximum power point and therefore the highest possible yield.
If we take as an example a photovoltaic module in which the data provided by the manufacturer are: 53 Wp to 17.4 V and 3.05 A.
When we connect the module directly to a battery with a voltage between terminals that, at this time, is 12 V, the module is actually delivering power
P actual = 12 V · 3.05 A = 36.6 W
That is, which of the 53 W available when a battery is loaded directly with 12 V across only advantage 36.6 W, which implies a 30% power loss.
The question is: where is the rest of Watts are missing?
The answer is nowhere because the generation module is not current and power.
The solution: get the maximum power of the photovoltaic module using charge controllers with a search engine maximum power. In this search, the subsequent voltage compensation intensity develops.
Last review: April 8, 2016