A solar charge controller is an essential component in most solar power systems, particularly those that charge batteries. Its necessity depends on the system configuration and the specific application. Here are the key functions and considerations that highlight the importance of a solar charge controller:
- Battery Protection: The primary role of a solar charge controller is to regulate the charging of batteries by controlling the voltage and current from the solar panels. This regulation is crucial to prevent overcharging and deep discharging, both of which can significantly reduce the lifespan and efficiency of the batteries.
- Maximizing Efficiency: Advanced charge controllers, such as Maximum Power Point Tracking (MPPT) controllers, optimize the power output from the solar panels. They adjust the electrical operating point of the modules or array to deliver the maximum available power to the batteries or the load.
- Load Management: Many solar charge controllers also offer load control features, providing over-discharge protection for the battery by shutting off the load when the battery reaches a critically low state of charge. This feature is particularly useful in standalone systems like solar street lights or remote telemetry units.
- System Monitoring and Control: Modern charge controllers often include display screens and connectivity options for monitoring and controlling the solar power system. They provide valuable information about the system performance, such as voltage, current, state of charge, and energy production.
- When a Charge Controller is Not Necessary: In very small systems, such as those with small maintenance-free batteries or in solar direct applications where batteries are not used, a charge controller might not be necessary. For instance, a small solar panel used solely to maintain a charge on a vehicle or boat battery may not require a charge controller.
- Grid-Tied Systems: In grid-tied solar systems, where the primary objective is to feed electricity back into the grid rather than charging batteries, a charge controller is not required. Instead, these systems use grid-tie inverters which convert the DC electricity produced by the solar panels into AC electricity compatible with the grid.
When should you use a solar charge controller?
Before installing a charge controller, you can test your PV system to test if it is necessary to install the controller.
Take your solar battery Amp Hour capacity and divide it by the maximum power amp rating of your solar panel. If you get an equivalent of 200 and above, you do not need a charge controller. If you get something below 200 then you need a charge controller.
For example ,if your battery is 100 amp hour and a solar panel is 10
you will divide the 100 amp hour and divide it by 0.6
In this case, since the quotient is below 200, you need a charge controller.
If yyoursolar battery is 100 amp hour and the solar panel is 5 watts, you will find the quotient by dividing;
In this case, the quotient is above 200, you , therefore,don’t need a charge controller.
The two cases demonstrated above are possible theoretically. Furthermore, these figures are created in the lab. Some variations might affect your solar battery.
- All solar batteries regardless of the quality starts to deteriorate after some time. For this reason, they might start discharging too fast.
Charge controllers regulate the discharging rate of solar batteries by holding some charge when the sun is not available. Your solar battery is therefore protected from being completely drained.
- The sun might be too hot which ends up sending more charge to the battery. If the solar battery is not connected to a charge controller, it will overcharge which might cause a fire.
- If you have several solar bbatterybackups, you might store some of them for emergencies. Solar batteries even when not in use will still discharge.
To prevent these batteries from running dry, it would be better if you connected them to the charge controller.
Generally, even if your solar PV system can sustain itself without a charge controller, to ensure your batteries are well protected, pair it with a charge controller. Solar batteries are very expensive.
What are the alternatives to solar charge controllers?
Charge controllers have specific roles in your solar PV system: To protect your solar battery from overcharging or over-discharging
No other device can fulfill the same purpose unless you pair solar PV with an all-in-one hybrid Inverter. An all-in-one hybrid Inverter has an inbuilt charge controller and still performs the role of an inverter.
How to use a solar charge controller?
A charge controller works by regulating the voltage of the solar battery. There are two types of charge controllers: MPPT and PWM. These two charge controllers can be connected tin he same way. The only difference is where you use them. Below is a step-by-step process of connecting a charge controller.
Step 1: Choose your charge controller
There are a few things you should consider before buying a solar charge controller;
- The sizing of the controller
- Does the charge controller offer an online status monitoring option?
- Does your solar charge controller have built-in GFT and arc fault.?
- Can you use the charge controller manually or automatic EQ?
- Is your charge controller capable of charging a 12-72V solar battery?
- Can you use your charge controller wind, solar or hydro mode?
- Does your charge controller hyper VOC extend the VOC limit?
Any quality charge controller should have the features mentioned above.
Step 2: Connect a fuse to the solar battery
Each charge controller brand has a specific way of installation. Check the user manual provided by the manufacturer.
You will however need a;
- Hot glue gun
- Wire crimper and
- A screwdriver
The first connection is placing the fuse in the positive cable of the solar battery. You should use a fuse calculator to size the right fuse for your connection.
Step 3: Connect the solar battery cables to the charge controller
The positive cable of the solar battery should be connected to the negative plug of the solar charge controller. And, the negative cable to the positive plug.
Step 4: Connect the solar battery cables to the solar battery
Connect the positive cable to the positive terminal and the negative cable to the negative terminal.
Once the connection is complete, the charge controller light will turn on provided the solar battery has some charge.
Solar charge controller settings
Different solar charge controller manufacturers list the settings of their devices on their websites or their user manual. These settings include the charge voltage and current.
These settings parameters are listed to help you utilize the charge controller capability to the maximum. They also help you protect your solar batteries. Some of these critical settings of a charge controllers include;
- Float voltage,
- Absorption voltage,
- Equalization voltage,
- Absorption Duration,
- Re- Bulk Voltage offset,
- Maximum Absorption Time,
- Equalization current percentage,
- Tail current,
- Automatic Equalization,
- Equalization stop mode,
- Low-Temperature cutoff,
- Temperature compensation
- Maximum Equalization Duration
If you can’t interpret these settings, send an email to your manufacturer with the description of the battery type, battery voltage ,and the number of solar panels.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as a Solar Electrical Engineer for several multi-national solar energy companies.
He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research.
He now shares his 20 years of expertise through his articles on the walkingsolar website.
Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.