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A typical solar system has the charge controller situated between the solar panels and battery. But is it that necessary? Can you connect solar panels directly to a battery? What would happen if you do?
A solar panel generates up to 20 volts, which is higher than the 12 volts required by a battery. Connecting the solar panels directly to the battery could overcharge and damage the battery.
What Happens if You Connect Solar Panels Directly to a Battery?
When sunlight hits the cells on a solar panel, it produces a chemical reaction and generates direct current (DC). The solar panel transmits this current into the battery. The current is used to charge the battery and can also be used to run appliances and other devices.
If the solar panel is directly connected to the battery, all of the current is placed in the battery. A 12V battery needs only 12 volts, at most 14.4.V to charge. A 12V solar panel produces up to 20V.
If you put 20 volts in a 12 volt battery, it will overcharge. This is going to damage the battery and whatever device or appliance is connected to it.
By installing a charge controller like the Binen 20A Charge Controller , this can be avoided. You place the charge controller between the solar panels and the battery, and it will regulate the current flowing into the system.
Why a Charge Controller is Needed to Connect Batteries to Solar Panels
A charge controller manages the electrical current going into the battery, keeping it at a safe level. This device ensures the battery charges at the optimum level without risk of overheating or overcharging. Some of the most important features of a charge controller are the following.
- Display: the controller should display the solar panel amps, battery bank voltage and charge level.
- Customizable lighting control: for simplified operation
- Auto low voltage connect / disconnect: turns on when the battery is charged and turns off when power is low
- Multistate Charging: adjusts the battery power according to the battery’s charge level for optimum performance.
The battery installation depends on the solar panel system design. A lot of home solar panel systems today come with an inverter that simplifies battery configuration. If your system does not come with battery expansion capability, you have to replace the inverter.
Lead acid batteries are the most widely and with good reason. Their electrical storage capacity is large and they discharge fast. However, lead acid battery levels should not drop below 50% as it will shorten the lifespan.
Lead acid batteries often have 2 V voltage and made up of cells that generate the required power. In solar power batteries, that is 12 volts. These are called deep cycle batteries because they charge during the day and discharged at night.
Sot the best way to avoid this is to install a charge controller. The controller will protect the battery and ensure only the right amount of current goes into the system. The following step by step guide shows you how it is done.
How to Connect a Charge Controller to a Battery and Solar Panel
Instead of connecting a battery directly to a solar panel, you should install a charge controller between the battery and solar panel. The solar panel will charge battery with current but the controller ensures only a safe amount goes into it. The following steps show how it is done.
Required Tools and Materials
- Solar panel
- Charge controller
- Battery charge
- Inverter (if you will use AC powered appliances)
- Cable, wires and connectors (these should be included in your solar panel kit)
- Crescent wrench
- Electrical tape
- Wire cutter
- Eye protection (goggles are recommended when working with lead acid batteries)
- 12V deep cycle battery – we recommend CHINS 12v 200ah LifEPO4 Deep Cycle Battery
The basic steps are:
- Connect the charge controller to the lead battery.
- Link the lead battery into the inverter.
- Connect the charge controller to the solar panels.
- To run, use the inverter to convert DC to AC, Clamp to the battery and turn the inverter on.
Step by Step Instructions
1. Prepare all the tools and materials. Set up the solar panel so you can link them to the main connector later on. Lay out the panels first. Depending on your setup, an extension cord may or may not be required.
The wires should be covered for protection. If the battery is not yet charged, do this first. It’s a good idea to charge the battery while you set up the solar panels to save time. Make certain the battery’s negative terminal is on one side and the positive terminal on the other.
If your battery is already parallel, proceed to step 3. If not, cut the cables and make some jumpers. The bigger the inverter, the longer the cable, but chances are your solar panel already has cables ready.
2. Hook up the charge controller onto the lead battery. There should be a wire on the controller that you can hook up or clamp onto the battery. The inverter must be turned off first. If the controller is waterproof you can position it anywhere. If it isn’t, make sure it is in a secure location.
Charge controllers come with digital displays for easy access to your system, so the best place to install it is in your RV. When installed properly, you can use the controller to monitor the energy situation in your RV.
3. Hook up the lead battery to the solar inverter. The battery can be configured parallel to the other batteries in the system. To add more batteries, connect them with cables. Make sure the cables are linked to the proper terminals.
4. Link the battery controller to the solar panel. Run the line from the panel to the controller and it should be set. Depending on your setup, an extension cord may be required to connect the components.
Tips and Warnings
To test the system, turn on the inverter to convert DC to AC. Clamp to the battery and then activate the inverter. If everything is in order the system should run fine. Try different devices and check for signs of problems. Here are some more suggestions:
- If you already bought a solar kit, follow the instructions given. Keep in mind that some of the steps in your solar panel kit may differ slightly. If you don’t want to manually put the whole thing together, look for solar panel system kits that require very little setup.
- Double check the wiring and cables. Make certain the connectors are tight and in the proper locations.
- Run a test first to see if it works. Keep an eye on the charge controller and check if it’s controlling the voltage.
- If the system does not run, check the wiring or if there is a loose screw somewhere. It is also possible the batteries are not installed correctly so look there first.
- Your solar system kit comes with a manual and troubleshooting guide so use that as reference.
How Long Does a Solar Panel Take to Charge a 12V Battery?
The charging time depends the solar panel watt capacity and how much sunlight is available. It also depends on the battery and how much power is required.
A 12V 100ah battery holds up to 1200 watts. A 100 watt solar panel can produce 600 watts with six hours of sunlight. So if the weather is ideal, a 100W solar panel can recharge a 12V 100ah battery in two days.
That assumes the two days have full sunlight so the solar panel can produce 100 watts for six hours. In reality this can only happen under the most ideal situations . Passing clouds, shading and other factors affect solar power output. if the conditions are not good, it might take 3 days or so to recharge the battery.
What are the Parts of a Solar Power System?
Now, let’s take a look at the 4 main components: the solar panels, the charge controller, the inverter and the battery. The following information makes it clear why you should never connect the batteries directly to a solar panel, unless it runs off DC power.
Solar Panel. These are the most recognizable parts of a solar system. Also called solar stations or solar cells, these are available in different configurations. The most popular solar panels are those with 36 cells, capable of producing 18 to 21 volts.
Inverter. Solar panels produce direct current (DC) which is then stored in the battery. To use this power for home appliances, you need an inverter to convert it into alternating current (AC). The inverter must be joined to the battery before it is connected to other AC appliances or devices.
Your solar battery generates 12 volt power, but the inverter changes this into 120 volts, making it usable and compatible with electrical devices. Inverters come in various forms and some are bundled with portable solar system kits.
Battery. The battery serves as the repository of all the energy that the solar panel produces. For RVs and home use, a 12V, deep cycle battery is recommended. These batteries can handle several discharges, which is what you’ll be needing. Without the battery, there is nowhere to store all the power the solar panel generates.
Solar Charge Controller. A battery charge controller acts as a voltage regulator for your solar power system. Think of the voltage regulator that you use with your computer and you get an idea of what a batter charge controller does.
Connecting solar panels to the battery is a simple, straightforward process, provided you know the steps. A lot of the mistakes people make is not taking the time to learn how a solar panel system works with the batteries. By understanding the process you’ll save yourself a lot of trouble – and dollars – later on.