Can we connect solar panels to a battery directly?

Solar panels produce electricity from sunlight. But it can’t store the generated energy. As it only works in the presence of the sun, we need to store the produced energy. And what else can we think of when it comes to storing energy! So, batteries need to be connected to the panels. In almost every case, there is a battery that’s connected to the solar panel. The battery gets charged from the panel and stores it until it’s being used by the device. And you know that our off-grid or standalone systems are also connected to batteries.

But, we can’t just connect the solar panels to the battery directly. We need some other devices to do the job. The panels should not charge the batteries directly if it doesn’t have an inbuilt charge controlling system.

Why can’t we connect a solar panel to a battery directly?

Solar panels send electricity to whatever it is connected to, may it be batteries. But the problem is it cannot control the procedure. The whole charging procedure should be controlled enough to keep the battery safe. If the panel doesn’t have an inbuilt charge controlling system, it can’t control the flow of electricity sent to the battery, which can harm the battery. Two kinds of problems can arise due to this.

· Overcharging

Directly connected panels send power to the batteries at a constant rate every time. And the flow doesn’t stop even when the battery is fully charged. It can cause overcharging and overheating. This can damage the battery, destroy the battery liquid, and shorten the battery life. Any kind of charge controller can fix this problem.

· Back-feeding

When the panel is not sending enough electricity, i.e., can’t generate enough, it can flow in reverse. The flow of electricity in the reverse direction will discharge the battery. So, your battery will lose charge at night or during cloudy weather. Some switch or diode that only allows one directional electric flow can fix this issue.

The physics behind them

A 12-volt solar panel can output 21 volts around a sunny morning. But a battery of 12 volts can tolerate a maximum of 14.4 volts while charging. If your panel is larger, it can fry the battery overcharging. We know that electricity always flows from higher to lower potential. The solar panel is set to higher potential when it is active (generating power). The larger the panel, the higher the potential. Higher is the potential; higher is the risk. Even when the battery is fully charged, the panels are set to a higher potential. So, the electric flow doesn’t stop for a fully charged battery. This is why the battery gets overcharged.

But when the panels are not active, the potential gets lowered. But the battery voltage remains the same. So, now electricity flows in the reverse direction, resulting discharging of the battery.  

What can happen if we still make a direct connection?

As I said in the previous section, a 12-volt panel can produce a 21-volt output voltage during the peak sunlight moment of the day. But the battery can’t tolerate the voltage exceeding 14 volts. So, it may boil your battery simply. The liquid of the battery will get dried and be damaged beyond repair in the worst case.

If the consequence isn’t that much, it is still harmful to your battery. The more times it faces overcharging and overheating, the shorter the battery life. It will keep losing its charge very soon, even after being fully charged. The battery capacity will keep lowering as the liquid inside will keep drying bit by bit. The liquid can even leak out from the battery cell. Bad optimization can lead to both undercharging and overcharging. Undercharging is also harmful to the battery.

In which cases we can connect solar panels directly

The main reason for which it’s not recommended to connect solar panels directly to the battery is the huge voltage difference between them. The output voltage and power rating of solar panels are generally much higher than those of a battery. But in the case of low power rating panels, it’s safe to connect the battery with them. When you connect a low-powered panel with a battery, the voltage is set just above the battery voltage.

So, there is the least risk of overcharging and overheating. At least it won’t ruin your battery. If, in any other case, the output voltage of the panel and the battery voltage match, then it is safe to connect them directly.

But still, the risk of back-feeding doesn’t reduce. So, it’s always better and safer to use switches. Otherwise, you may disconnect them accordingly. You must keep checking whether the battery is fully charged and disconnect when. Also, check the voltages using a multimeter from time to time to be safe.

What do you need to charge with solar panels? The setup

· Charge controller

The charge controller is a device that is solely used to protect the battery from overcharging. It controls how perfectly the battery is charged. There are two main variations; PWM (Pulse Width Modulator) and MPPT (Maximum Power Point Tracker). MPPT is a new technology, and it connects the system with a variable resistance that keeps a check on the voltage. Also, it is a very efficient device, so much energy can get wasted.

It works as follows:

When the power increases, it adjusts accordingly so that the output doesn’t change much. It also measures the changing voltage and current and predicts the effect. In this way, it can track the changes in power and work more efficiently.

PWM hovers the charging voltage of the battery at around 14.4 volts. But MPPT ones are 30% more efficient than the PWM ones. On the other hand, PWM ones are less costly.

· Battery maintainer

A battery maintainer sends a charge only when a battery can accept a charge. So, there isn’t any chance of the battery getting damaged due to overcharging. As the battery reaches the fully charged condition, it stops sending electricity. Unlike a battery charger, battery maintainers flow electricity at a slow rate into a battery and keep it working.

It also protects the batteries from overheating and surges due to charging or over usage. Battery maintainers feed the batteries but don’t overfeed. In general, it isn’t healthy for a battery to use while charging it by a regular battery charger (it may lead to overheating followed by serious damage to the battery and sometimes the gadget too).

But in the case of a battery maintainer, it is simply okay to use the battery and the gadget while charging it. Solar battery maintainers are good for maintaining the battery at its peak power supply condition rather than charging a dead battery to its full life. When used properly and in conjunction with regular vehicle upkeep, you can optimize the lifespan of the battery and save big over time.

Things to consider when setting up a battery with solar panels

There are certain things to consider while choosing a charge controller. The very first thing I would suggest is to check the Low Voltage Disconnect (LVD) and Load Reconnect Voltage (LRV). For a 12-volt battery, LRV is generally one volt higher than the LVD.

There are charge controllers with read-only displays and interactive displays, and I’ll suggest my readers go for a charge controller with an interactive display. In the case of a read-only display, it only shows it’s an activity that you have nothing to do with. But in the case of interactive display, you can program the mechanism of the controller accordingly with your need, voltage supply/needed, thunder, etc.

You may consider checking some other facilities like whether it can indicate a short circuit, low battery, battery full, high temperature, and other such things.

Charge controllers with a wide temperature range may cost a bit higher, but they ensure constant service in every season. Otherwise, it may fail in some particular season. Also, it depends on which geographical area you belong to.

It should have an automatic recovery system without fuses.

Last but not least, keep information about the various certifications of solar charge controllers.

Solar battery chargers

Solar battery chargers available in the market can charge your battery directly. Even though they are portable, you can still install them on your rooftop if you need to. There are different-sized chargers that can serve different purposes. Popular uses include charging solar batteries for cars, boats, phones, and laptops.

The main advantage of using a portable solar charger is that it works anywhere it gets enough exposure to the sun. As usual, it doesn’t work 24/7, just like any other solar device. Also, it doesn’t charge your battery as quickly as any power outlet. Small electronic devices work well enough with a charger of 5-volt output. But larger devices like laptops need a portable battery pack with a 12-24 volt output rating and a similar battery charger.

Solar trickle chargers are some special kinds of solar chargers that don’t only charge the battery but also protect it from back feeding (stops self-discharging). It instead maintains the battery life instead of charging a dead battery to life.

How do solar chargers work?

Solar chargers contain solar cells that absorb sunlight to produce electricity. This electricity flows from the charger to your device’s battery to charge it. Many chargers can’t directly push electricity into the battery. So, the device often includes an onboard extended-life battery pack to serve the purpose. Also, the battery shouldn’t be in use while charging it.

This system allows the battery to send electricity to other devices when it is not charging (at night time or in bad weather). Some devices don’t use DC electricity to charge their battery (generally, the charging procedure uses DC electricity). To charge those devices, you’ll need to use a charge inverter that switches the DC electricity to the AC one.

It will make the solar charger more versatile. These small portable solar chargers contain USB connections most of the time. So, they can be directly connected to small devices like cellphones, tablets, USB lights, and other devices that are capable of charging through USB. These portable ones are not as powerful as your household power system. It has limited uses. Also, it is time-consuming to charge through portable chargers as the charging procedure is very slow.

How vulnerable does the battery really be?

Your batteries are not maintenance-free. They are electrochemical devices that need to be checked within a certain time interval and need proper care. They are sensitive to the temperature, charge level, and environment.

You should always avoid overcharging and overheating the battery. You should never drain all the charge of your battery and make it completely dead before charging it. The ambient temperature also puts the battery.

If it’s too hot outside, then the battery is more likely to get overheated. All these things shorten your battery life. Excessive charging or heating can make the battery even explode. So it needs regular maintenance for a long lifespan and good service. Different kinds of batteries face different issues and need somehow different maintenance. You may check that for your battery.

Conclusion

We discussed the problems that can arise if you connect your battery directly to a solar panel and the potential solutions. It’s not recommended to do that except in some cases. For beginners, it’s always safe to be extra careful. Though you can’t make a direct connection, some devices make your task easier. Go for them.

And always be specific about your need so that you can find the most appropriate thing and set it up for your device or system. You’ll find every kind of charger according to your need. So, don’t forget to do a little research before buying a portable charger or other devices for your system.