Why Lithium Battery technology is suitable for power backup ?

Main chemical component

Lithium Battery technology are different from other chemistries due to their high energy density and low cycle cost. Lithium batteries come in about six common chemistries, each with its unique strengths and weaknesses. For renewable energy applications, the main chemical component is lithium iron phosphate (LiFePO4). This chemistry offers excellent safety, excellent thermal stability, high current ratings, long cycle life, and abuse resistance.

Stable lithium chemistry

Lithium iron phosphate (LiFePO4) is extremely stable lithium chemistry compared to almost all other lithium chemistries. The battery is assembled from a naturally safe anode material (iron phosphate). Compared to other lithium chemistries, iron phosphate promotes strong molecular bonds that can withstand extreme charging conditions, extend cycle life, and maintain chemical integrity over multiple cycles. That’s why lithium iron phosphate batteries have excellent thermal stability, long cycle life, and resistance to abuse. LiFePO4 cells are not prone to overheating and do not “thermal runaway”, so they will not overheat or burn when subjected to mishandling or harsh environmental conditions.

Easy to storage

Unlike submerged lead-acid batteries and other battery chemistries, lithium batteries do not emit dangerous gases such as hydrogen and oxygen, nor do they have the risk of exposure to corrosive electrolytes such as sulfuric acid or potassium hydroxide. In most cases, these batteries can be stored in a confined area without risk of explosion, and a properly designed system does not require active cooling or ventilation.

Adjustment Lithium pack to different voltage

Lithium batteries are components made up of many batteries, such as lead-acid batteries and many other battery types. Lead-acid batteries have a nominal voltage of 2V/cell, while lithium batteries have a nominal voltage of 3.2V. So to achieve a 12V battery, four batteries are usually connected in series. This gives LiFePO4 a nominal voltage of 12.8V. 8 cells are connected in series to form a 24V battery with a nominal voltage of 25.6V, and 16 cells are connected in series to form a 48V battery with a nominal voltage of 51.2V

Lithium Battery technology are used as VRLA battery replacement

Lithium Battery technology are often used as a drop-in replacement for lead-acid batteries because they have very similar charging voltages. The maximum charging voltage of a four-cell LiFePO4 battery (12.8V) is usually between 14.4-14.6V (depending on different manufacturer standards). Lithium batteries are unique in that they do not need to absorb a charge or maintain a constant voltage state for long periods of time. Usually when the battery reaches the maximum charging voltage no more charging is required. The discharge characteristics of lithium iron phosphate (LiFePO4) batteries are also unique. During discharge, lithium batteries will maintain a higher voltage than lead-acid batteries typically under load.

Lithium Battery technology do not need to be fully charged on a regular basis

A significant advantage of Lithium Battery technology over lead-acid battery is that they do not suffer from insufficient cycling. This is a situation where the battery cannot be fully charged until it is discharged again the next day. This is a very big problem for lead-acid batteries, which can cause significant plate degradation if cycled in this way over and over again. Lithium Iron Phosphate (LiFePO4) batteries do not need to be fully charged on a regular basis. As a practical matter, the overall life expectancy of the battery can be improved with a small partial charge rather than a full charge.

Lithium Battery technology efficiency

Lithium Battery technology efficiency is a very important factor when designing a solar power system. The round-trip efficiency of an average lead-acid battery (full to empty to full) is about 80%. Other chemicals may be lower. The round-trip energy efficiency of lithium iron phosphate batteries is as high as 95-98%. That alone is a major improvement for a system that lacks solar power in winter, and generator charging can save a lot of fuel. The absorption charge phase of lead-acid batteries is particularly inefficient, resulting in efficiencies of 50% or less. Considering that lithium batteries do not absorb charge, the charging time from full discharge to full charge can be as short as two hours. Lithium batteries can be discharged almost completely at their rated value without significant adverse effects.

BMS Protection

In lead-acid batteries, current will continue to flow even when one or more of the batteries are fully charged. This is the result of electrolysis that occurs within the battery, where water is split into hydrogen and oxygen. This current helps to fully charge the other batteries, naturally balancing the charge on all the batteries. However, a fully charged lithium battery has a very high resistance and will flow very little current. The lagging battery is therefore not fully charged. During balancing, the Battery Management System BMS will apply a small load to a fully charged battery to prevent it from overcharging and allow other batteries to catch up.

Conclusion

Lithium Battery technology have many advantages over other battery chemistries. They are a safe and reliable battery solution without the fear of thermal runaway and/or catastrophic meltdown, an important possibility for other lithium battery types. These batteries offer extremely long cycle life, and some manufacturers even guarantee the battery can be cycled up over 3,000 times. With continuous discharge and charge rates up to C/2 and round-trip efficiency up to 98%, it’s no surprise that these batteries are gaining popularity in the industry, and Lithium Iron Phosphate (LiFePO4) batteries are a perfect energy storage solutions.