Choosing a Solar Lithium Battery
There are a few considerations when choosing which solar battery type to install. These include the battery’s cycle life, depth of discharge and storage environment.
Inconsistent charging can damage lead-acid batteries, while this has minimal effect on lithium batteries. Additionally, lithium batteries can withstand cold temperatures while delivering clean energy around the clock.
Lithium Ion Batteries
Lithium-ion is the most common battery type used in solar energy storage systems. They are typically more expensive than lead acid batteries, but they have a longer lifetime and higher efficiencies.
When choosing a solar lithium battery, you’ll want to consider its depth of discharge (DoD) and capacity. Most lithium batteries can be charged and discharged to about 80% of their total capacity before the battery begins to degrade. This is significantly higher than the 50% maximum DoD of most lead acid batteries, and it allows you to get the most out of your solar system.
A good solar lithium battery will also have an internal battery management system (BMS). This BMS protects your batteries from fluctuating voltage, current, and temperature conditions that could otherwise cause damage to your solar lithium battery cells.
In addition to the BMS, a high-quality solar lithium battery will have a protective circuit that limits cell voltage during charge and prevents the cell from dropping below its design limit during discharge. This helps to prevent metallic lithium plating, which can reduce the life of your battery.
As a result of these safety Solar Lithium Battery features, solar lithium batteries are one of the most popular choices for home solar energy storage and are widely available at big box stores, online retailers, and automotive dealers. They are also eligible for federal and state incentives such as the 30% solar tax credit, making them an affordable choice.
Lithium Iron Phosphate Batteries
Lithium iron phosphate batteries, or LFP batteries, are the latest solar battery of choice for off-grid solar systems and backup power. These batteries offer numerous advantages over lead-acid and lithium ion, including longer lifespans, higher temperature tolerances, true deep-cycle ability, safety and ease of use.
LiFePO4 batteries have a low self-discharge rate, which means they will hold their charge longer when sitting idle. This is important for a backup solar system, where batteries may be left unused for months at a time, but are ready to be deployed in the event of a blackout or other grid disruption. Lithium iron phosphate batteries also have a high DoD (depth of discharge) rating, which means they can be discharged to 80% without losing capacity or damage.
On a bookshelf in his home near Montreal, Denis Geoffroy keeps a small vial of lithium iron phosphate, a slate gray powder that he made nearly 20 years ago while helping the Canadian company Phostech Lithium scale up production for use in cathodes, the positive ends of batteries that contain the active materials used to create energy. He now hopes to help American Battery Factory, a Utah-based company that plans to serve the stationary energy storage market, by producing cathodes for its proposed cell factory in Arizona.
This will allow the company to source its cells from a single supplier, and cut costs while increasing quality and reliability. With lower prices and improved efficiency, LiFePO4 batteries are quickly replacing lead-acid as the new standard in solar backup power.
Flow Batteries
Flow batteries, also known as redox flow batteries, are electrochemical cells with two liquid solutions (anode and cathode) pumped adjacently past each other through a membrane, generating a charge by transferring electrons back and forth between the two. Flow batteries can store energy at higher capacity and longer duration than other solar lithium batteries.
Currently, most commercial flow battery systems use vanadium as the liquid electrolyte. The 23rd element on the periodic table, vanadium has a unique property of being Solar Lithium Battery able to hold and lose electrons without losing its material properties like other battery cell materials degrade over time. Currently, most flow battery applications for solar include load leveling and stabilization on the electricity grid for electric power companies or as uninterruptible power sources at factories and offices.
Flow batteries are relatively expensive to purchase and build, largely because they require large tanks of the electrolyte solution, which must be cooled and regulated. However, once operational, they have a lower levelized cost of storage than other solar lithium batteries. The long duration of iron flow batteries makes them ideal for storing renewable energy and providing back-up power at industrial or critical infrastructure sites. The size of an iron flow battery is a fraction of the size of Li-ion batteries, and can fit into a standard shipping container.
Lead Acid Batteries
Lead acid batteries cost less up front but require regular maintenance and don’t last as long as lithium battery chemistry. Lithium Iron Phosphate (LiFePO4) batteries, on the other hand, have a longer lifespan, are more efficient, and require no venting or watering.
In a lead-acid battery, negative lead plates (anodes) are connected to positive lead dioxide plates (cathodes) and separated by an electrolyte – a mixture of sulfuric acid and water. The reaction between the anode and cathode creates a solid of lead sulfate on each plate that is surrounded by the electrolyte. The current supplied by the charger reverses this reaction and converts the sulfate back to lead. This causes a gassing of hydrogen and oxygen, which is why batteries are typically vented to prevent an explosion hazard during charging.
It is important to check a lead-acid battery’s water level regularly and add water as needed. The leaking hydrogen and oxygen gasses produced by the battery during charging can cause damage and reduce battery life.
Adding more electrolyte to the battery can make it more resistant to water loss, but it will also increase the weight of the battery and decrease its energy density. Other designs, such as AGM and gel batteries, use a ‘captive electrolyte’ to immobilise the sulfuric acid and minimise gassing. This makes them less sensitive to temperature variations and easier to maintain but they still don’t have the high power output of lithium batteries.
