Solar Charge Controller is a device used to protect the batteries in a solar electric system from being overcharged or being over-discharged.
Overcharged batteries have a much shorter life time than well cared for batteries since the electolyte is boiled off as gas and lost. Overly discharged (i.e. flat) lead acid batteries become permanently damaged, so a solar charge controller is used to disconnect any load when the battery is discharged down to a safe cut off voltage.
LEDs and (in the more expensive controllers) LCD displays are used to show the current state of the charge of the battery, the state of the current entering the batteries from the solar panel(s), and the current being drawn from the battery by loads.
There are some of the most sophisticated, flexible and full featured controllers currently on the market. However, if you strip away the fancy features and displays, Wellsee solar controllers carry out the exact same basic task as almost all of their cheaper and less sophisticated cousins.
If we were to look at the job description of any solar controller, the first item (and in some cases the only function) is to prevent the battery bank from being over charged. The controller does this by simply disconnecting the solar panels from the battery. So at a really basic level, the controller is just a switch.
Clearly we want the controller to disconnect the solar panels only when the batteries are fully charged. To do this it must employ some intelligence and have some understanding of battery technology. The dumbest of controllers simply watch the battery voltage until it reaches the regulation point (battery maximum voltage) it then switches the panels off.
Most controllers have a bit more smarts than this. With some understanding of how batteries like to be charged, it is more reasonable to allow the battery voltage to rise to the regulation point, then carefully regulate the charge from the panels to hold the voltage at this point for a time (normally 1 – 2 hours). This is referred to as the absorption phase. This absorption phase typically takes the batteries from 92% up to fully charged.
After this absorption phase is complete, a smart controller will drop down into float mode. In this float mode the controller is letting just enough charge from the panels through to the batteries to keep the battery voltage up at its float point.
So this is the three stages that we hear about when the sales people are trying to convince us to pay for a smart or “three stage” solar controller (or battery charger).
1.Bulk – push as much power into the batteries as possible.
2.Absorption – control the charge to hold the battery voltage at a point for an hour or two.
3.Float – maintain the battery at close to full charge by controlling the charge and holding the battery voltage at a preset point.
Most controllers present some kind of information display. At the most basic level this is simply a couple of colored lights that give you some idea of the stage that the controller is currently in. The Wellsee controllers have LCD displays that users can adjust voltage manually.
Footnote – Plasmatronics has recently announced their new controller, the Dingo. This shares many of the advanced features of the PL series and has the advantage of regulating on the positive side and having a nice fully enclosed case.
A charge controller is not always required if the maximum current going into the battery is not more than 10% of the batteries Ah capacity (C/10) - i.e. if the battery is 60Ah then a charge controller is certainly required if the current from the solar panel is likely to exceed 6 Amps - as long as you make sure you don't over-discharge the battery.Some suggest a charge controller is required if the maximum current from the solar panel is just 1% of the Ah capacity (C/100) of the battery bank.
Good quality solar charge controllers are up to 30% more efficient than basic 'on-off' controllers as they have provide pulse width modulated (PWM) battery charging. When the voltage of the battery bank reaches the regulation voltage (14.1V), instead of stopping charging altogether, the patented PWM algorithm reduces the charging current and continues charging slow enough to prevent the battery overheating or gassing.
PWM helps to get the batteries charged up to well over 90% capacity, extends the life of the battery, and means that more of the power generated by the solar panels is stored. Since the batteries store more energy on average, a smaller battery (or less batteries in a battery bank) can be used reducing overall system costs.
With solar charge controllers you really get what you pay for. It is well worth spending a few pounds extra to buy a good quality PWM controller from the start since it will pay for itself by getting more energy into your batteries and by protecting the batteries properly.
We have a range of high quality pulse width modulated solar charge controllers and mppt controllers on www.wellsee.cc, welcome to visit!