Solar Charge Controller
A solar charge controller is needed if you choose to store the solar panels electricity in solar batteries. As we all know the intensity of the sun energy is totally controlled by nature and there is no guarantee the electric solar panels will produce a constant amount of electricity. A reliable solar charge controller will allow the uncertain solar panels’ voltage to safely charge the batteries. Without this controller you can potentially overcharge your batteries and damage the devices connected to it. For lead acid batteries overcharging may lead to internal crystallization which reduces the batteries’ lifespan.
Most of 12 volt-rated electric solar panels produce 16 – 20 VDC. The average voltage needed by solar batteries to get fully charged is around 14V so without proper regulation the batteries will be damaged from overcharging.
You may also find solar batteries with 24 volt or other voltage rating; therefore it is important that the charge controller match the battery’s voltage.
When the batteries are fully charged the controllers – also known as regulator – will stop the batteries from getting further charged. A charge controller that has a low voltage disconnect (LVD) facility will also disconnect any load connected to the DC load terminal when a certain low voltage is detected to prevent the battery from draining down too far.
The quality of the charge controller may affect your battery’s lifespan. There are generally three types of solar charge controller:
- Simple controllers (1 – 2 stage controllers). This type controls the voltage in one or two steps by means of shunt transistors or relays. Basically they just short or disconnect the electric solar panels once a certain voltage is reached. Because they don’t have many components they are not easy to fail. This type is considered old but you may see some of them still running.
- 3-stage or PWM (Pulse Width Modulation) controllers. Unlike the simple controller that gives a steady output to the batteries, the PWM controller delivers a series of short charging pulses to the solar batteries. These charging pulses work as a very-rapid on and off switch. When the batteries are fully charged without load the controller will send its short pulse every few seconds but when they are discharged the controller will deliver very long pulse almost continuously or even work in fully “ON” mode. The PWM controller determines how long the pulse shall be and how fast it should send it by constantly checking the batteries charge status between pulses and do the self-adjustment when necessary. Due to these pulses the PWM controllers can easily emit noises that affect your TV, radio or other electronic devices.
- MPPT (Maximum Power Point Tracking). This type of controller is the most expensive one and can give up to 98% efficiency and can deliver up to 30% extra power to the solar batteries. When a solar panel is connected to a battery, the battery will limit the voltage output of the solar panel. Based on this condition you normally see two voltages listed on the back of your solar panel: The open circuit voltage, which is the panel’s voltage output in a full sun and the panel operating voltage which is the voltage of the panel after being connected to the solar battery. Panel operating voltage is lower than open circuit voltage. The reason why MPPT can boost the power up to 30% is because it can ‘fool’ the panels by eliminating their view of the batteries in the system so the panels will not drop the voltage output to the panel operating voltage.
the Solar Cost Admin
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