Solar charge controllers have many functions, some more advanced than others. However they all have a couple of functions that are essential in a DC battery solar system.
A solar charge controller will monitor the power from the panel and into the battery. For example, if the battery is full and the day is sunny, the controller will stop power from being forced into the battery which may cause damage.
When a solar charge controller is used, it is possible to leave connected even when charging from a hookup, generator, engine or other charging device. Once fitted it will self-regulate and protect.
More advanced charge controllers will learn the battery type and performance and increase efficiency over time
Therefore it will be necessary to connect a controller between the solar panels and the battery.
Charging voltages should be lower for gel type lead acid batteries, and should also be lower for batteries at a higher temperature. A charge controller may be able to be programmed for the particular type of battery and may also have the facility for a battery temperature sensor.
Types of Charge Controller
Charge controllers will vary in their sophistication but the main choices to be made are system voltage (though the controller may be designed for more than one voltage) and the maximum charge current (maximum current to be produced by the solar panels).
Charge controllers may also have a controlled DC output. This may be of use in a system without an inverter and will cut off the DC supply when the battery voltage is too low.
This facility is unlikely to be able to supply the current required for an inverter and as an inverter would have its own control, would not be necessary – an inverter would be connected direct to the battery.
The simplest type of charge controller would simply stop charging when the battery voltage reaches a certain level, and start again when the voltage drops. Most controllers however will use Pulse Width Modulation (short pulses of varying duration) to continue charging a battery to near its maximum, after a certain voltage has been reached.
A further development of the charge controller is the Maximum Power Point Tracker Controller which gives improved efficiency.
MPPT Solar Charge Controllers – a More Intelligent Controller
Maximum Power Point Tracker Solar Charge Controllers
A basic charge controller simply performs the necessary function of ensuring that your batteries cannot be damaged by over-charging, effectively cutting off the current from the PV panels (or reducing it to a pulse) when the battery voltage reaches a certain level.
The efficiency loss in a basic system is due to a miss-match between voltage produced by the PV panels and that required to charge the batteries under certain conditions.
A 24 volt battery will require upto about 28 volts to fully charge it. When the battery being charged is in a fairly low state, its voltage (under charge) may only 24 volts.
Our PV panels, which we refer to as 24 volt panels, need to be able to charge the batteries on a bright day (not only in full sunshine) so are designed to produce at least 24 volts in those conditions. In bright sunshine hover, these panels may be cable of producing 40 volts. In-fact, they are likely to produce their rated output power (volts x amps) at 32 – 34 volts.
When the battery is at 24 volts, it will be pulling the panel voltage down to 24 (assuming no voltage drop in your cables). This results in the panels producing significantly less than their rated output and therefore there is a loss in efficiency.
How Does MPPT Help
An MPPT controller, in addition to performing the function of a basic controller, also includes a DC voltage converter, converting the voltage of the panels to that required by the batteries, with practically no loss of power. In other words, they attempt to keep the panel voltage at their Maximum Power Point, while supplying the varying voltage requirements of the battery.
Furthermore, a 24 volt system with an MPPT charge controller may have the panels wired in series to produce 48 volts, maintaining the ability to provide some charging current in dull conditions, when a standard system would not provide any charge.
Manufacturers confirm upto 40% power increase from your panels using MPPT, which
A Maximum Power Point Tracker controller performs an extra function to improve your system efficiency.