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What Kind of Battery is Used for Solar Panels?

Solar energy systems are typically made of solar batteries and panels, mounting tools, and a monitoring system for the overall performance. The energy from the sun is collected by the panels that send the converted energy into the inverter from which you can utilize electricity in your home, office, or industrial area. These systems are more popularly used for backup among homeowners since most houses are tied to the grid. However, many people are looking for a replacement for their utility supply. One common reason why people are switching to solar is to steer clear of high-energy costs.

There are many types of solar batteries that are used as a back-up for critical loads in times when the grid experiences failure. Whether you’re interested in installing an instantaneous backup power like UPS or a high-powered one, you can select from the different kinds of solar batteries to use for your system. The solar batteries charged by these panels are engineered to serve as auxiliary service to the grid.

 

What is a Solar Battery?

 

A solar battery simply stores the energy generated by the solar panels in your energy system. They may have their inverter with an integrated energy conversion and performance monitor.

Also, the storage ability of different kinds of solar batteries corresponds to their capacity. Instead of returning solar electricity directly to your grid, the solar battery collects it for later use. When your battery is fully charged, the system will send electricity back to the grid. When the battery is used and its charge gets depleted, then the battery will resume charging and draw electricity from the panels once more.

Although batteries are typically connected to home solar energy systems for functioning, they don’t need solar panels to be useful for homeowners. The electricity from the grid can also charge the batteries in the case of small-scale solar energy storage. The solar battery is the storage portion of your solar panel system for the energy supplied by the panel to the home. In times when the solar panel isn’t generating any electricity, this battery will release its stored energy for your use.

If you stay completely off-grid, these batteries can provide 100 percent self-sufficiency that homeowners need as long as batteries get properly charged by the solar panels.

For businesses or homes where power outages could spell disaster, a solar battery bank can adequately compensate for this. This is true especially for areas where the grid supply is not as dependable or during extreme weather conditions where you’d absolutely need back-up. More and more people are opting for solar battery banks for power supply during times when utility prices reach their peak. Depending on your goal and desired outcome, you can employ this budding yet solid technology in your home or business.

 

Can Solar Panels Charge Lithium Batteries?

 

Yes. However, lithium batteries could be damaged by regular charging because of their charge response, among other things. Most kinds of solar batteries are charged in three stages, which are bulk, acceptance, and float. Lithium batteries, on the other hand, are charged in two stages.

The first is similar to the bulk stage for other batteries, where it is charged at a constant voltage until it is almost full. However, the charging amperage will be left to drain while it goes through the second and final stage of charging. Lithium batteries can also be destroyed by store charging as that can increase discharge and endanger battery life.

 

Different Types of Solar Batteries

 

Lead Acid

 

For several years, lead-acid batteries have been used as a reliable energy supply for off-grid areas. They are typically deep-cycle and inexpensive. Lead-acid batteries are attributed to high power and discharge current but low energy. They take long to charge completely – up to 14 hours.

These batteries must be disposed of correctly or they can be an issue to the environment due to their highly toxic nature.

Two types of lead-acid that are commonly used for solar panels: flooded and valve-regulated lead-acid (VRLA) batteries.

The flooded lead battery is a dependable option but requires watering and proper ventilation to function. The VRLA, which is equipped with valves for off-gassing regulation, comes as two types, gel and absorbed glass mat (AGM). These are suitable for cold and warm temperatures respectively. Although the VRLA batteries give enough flexibility for installation, their sensitivity to temperature may however pose a challenge to people looking for a permanent alternative to their grid supply.

 

Lithium-Ion

 

Lithium-ion batteries have become a more popular choice for solar systems all over the world. The development of this type of battery has a lot to do with its application in the electric car industry. Its prismatic form allows for ventilation and benefits use in solar systems.

Lithium-ion batteries have a unique voltage range and response to charging (two stages as opposed to the conventional three). They can be charged with a voltage regulator charge controller. Although lithium-ion batteries have a low self-discharge, they do not benefit from long-term charging.

This kind of solar battery is generally low maintenance, and has high specific energy with a long lifespan. Compared to lead-acid, lithium batteries usually cost more. In addition, they may require a protection circuit to regulate the current and voltage.

Generally, lithium-ion batteries can supply more cycles than lead-acid, making them great for delivering ancillary services to the grid. One energy-saving trait of lithium-ion, which makes it a good option for a solar system, is its high charge and discharge efficiencies. These batteries also lose less capacity when idle, which is useful in solar installations where energy is only used occasionally.

 

Other alternatives

 

Nickel Cadmium

 

Nickel-cadmium batteries are generally characterized by low maintenance and tolerance to a wide range of temperatures. They come in different sizes and performance levels, with long shelf life. However, this kind of solar battery has a high discharge rate and low energy density, which makes it a relatively poor choice for permanent off-grid supply. Also, it requires special disposal like lead-acid batteries, because of that danger its toxicity could cause the environment.

 

Sodium Nickel Chloride

 

Also called ZEBRA cell, the sodium nickel chloride battery has high recyclability with no emission at all. It requires no ventilation or maintenance. Its high energy density makes it a great backup option for grid supply.

 

Comparing Solar Batteries

 

When it comes to selecting which solar battery to use, you’ll have to consider some specific characteristics for a more detailed choice. Some things to consider are:

 

Capacity

 

Capacity simply describes the solar battery’s ability to store electrical power. Lithium batteries are characterized by higher capacity than all kinds of lead-acid batteries due to their higher weight. You will need about 8 lead-acid batteries to power a 5.1kW, while just two lithium-ion solar batteries will get the same job done. The higher energy density of the lithium battery means that it can be installed in hard-to-reach places, as they can fit more capacity into less space. You may face several challenges with lithium’s heavy weight if you’re installing these solar batteries yourself. Nickel-cadmium and sodium nickel chloride also both have a wide capacity range.

 

Depth of Discharge (DoD)

 

A solar battery’s DoD is the usable part of its capacity and a recommended DoD of at least 40% would give you optimal usage of the battery. Lead batteries generally have a DoD of 50%, while nickel-cadmium batteries are rated at 15%. Exceeding this mark before recharging will decrease a battery’s lifespan. Lithium-ion and sodium nickel chloride solar batteries, on the other hand, have 80% DoD, which implies a higher usable capacity.

 

Solar Battery Life & Warranty

 

When deciding which solar battery to implement in your system, its battery life is the best indication of its ability to preserve its capacity. One charge cycle is simply the charge back up from a discharge and it’s the main measure of the battery’s lifespan. Also, the number of cycles that your solar battery will go through will depend on the intensity of its use. This attribute will differ for even the same type of solar battery and is affected by the battery’s depth of discharge. A warranty is always a good sign of dependability in any brand or product, and that also goes for solar batteries.

 

Round-trip Efficiency

 

The round-trip efficiency of a solar battery is the difference between the available energy and the amount of energy used for charging it. Just like with the DoD, the higher a battery’s round-trip efficiency, the better. Lithium-ion solar batteries win when it comes to efficiency (95%) as they have the highest conversion rate of solar power to electrical energy. What this means is that you may need to install fewer solar panels and batteries depending on your system’s configuration.

The charge rate is another thing to pay attention to when selecting your solar battery, as it indicates the speed with which it will be refilled when connected to a charger. It’s a function of the capacity and expressed in fractions such as C/4. Lead-acid, with a charge rate of C/5, can take up to twice as long as lithium-ion solar batteries to charge, especially during the bulk phase.

With these parameters in mind, you can accurately plan and install your solar system. Depending on what you hope to use the system for (backup or main supply), you can choose which kind of solar battery would best serve you.

Flooded lead-acid and lithium-ion batteries are ideal for a full-time, off-grid supply of different levels of use. If you’re looking for a battery to use in your vacation home or somewhere you won’t be spending much time around the year, then the sealed lead-acid type is your best bet. It requires zero-maintenance and has a low self-discharge rate.

When selecting a battery for backup purposes alone, you have to consider the frequency of power outage on your grid supply to determine how many times it’ll be used throughout the year. If it won’t be used for more than a couple of times, then you will benefit more from a low maintenance battery like the sealed lead-acid solar battery. The lithium-ion type is best recommended for powering industrial sites where heavy use may be regular.

 

End of Life Solutions

 

Enterprise and utility-scale solar installations will have environmental regulation compliance concerns regarding not only the kinds of solar batteries used, but also the decommissioning of panels, recycling of racking, and disposal of inverters. A direct-to-refinery solar battery recycling approach ensures that disposal is handled responsibly.

A no-landfill disposal plan should comply with standards such as:

  • R2:2013
  • ISO 9001:2015
  • ISO 14001:2015
  • ISO 45001:2018

If your company is in need of bulk solar panel or batter disposal, in the terms of 100+ units, contact a solar recycling specialist at We Recycle Solar for more information.

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